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Title:
HYDRODYNAMIC ELECTROPROCESSING OF SOLUBLE CONDUCTING POLYMERS
Document Type and Number:
WIPO Patent Application WO/1998/038224
Kind Code:
A1
Abstract:
The present invention provides a process for preparing a soluble conductive polymer comprising the step of electrochemically polymerising a monomer and/or an oligomer, or two or more different monomers and/or oligomers, or derivatives thereof, in an electrolytic cell comprising monomer and/or oligomer solution, an electrolyte and an electrode assembly, wherein the monomer and/or oligomer solution is in a hydrodynamic relationship with respect to said electrode assembly. Also provided is an electrochemical cell and an apparatus for hydrodynamic processing of soluble electroconductive polymers as well as soluble conductive polymers prepared by the process disclosed herein.

Inventors:
Wallace, Gordon George (55 Acacia Avenue, Gwynneville, NSW 2500, AU)
Innis, Peter (7 Jarndyce Avenue, Ambarvale, NSW 2560, AU)
Zhou, Dezhi (1/87 Murray Road, Corrimal East, NSW 2518, AU)
Application Number:
PCT/AU1998/000133
Publication Date:
September 03, 1998
Filing Date:
February 27, 1998
Export Citation:
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Assignee:
UNIVERSITY OF WOLLONGONG (Northfields Avenue, Wollongong, NSW 2522, AU)
Wallace, Gordon George (55 Acacia Avenue, Gwynneville, NSW 2500, AU)
Innis, Peter (7 Jarndyce Avenue, Ambarvale, NSW 2560, AU)
Zhou, Dezhi (1/87 Murray Road, Corrimal East, NSW 2518, AU)
International Classes:
C08K3/00; C08F2/58; C08G61/12; C08G73/00; C08G85/00; C08L101/00; C25B3/10; H01B1/12; (IPC1-7): C08F2/58; C08G73/06; C08G75/00; C25B3/00
Foreign References:
JPS6160900A
JPS60203608A
JPS59207933A
US4502934A
US4968393A
JPS62274086A
JPS63317689A
JPS60137922A
Other References:
WEST C.D. - Essentials of Qualitative Analysis, page 224, (1987), McGRAW-HILL, XP002946486
See also references of EP 0963381A1
Attorney, Agent or Firm:
Baldwin, Shelston Waters (60 Margaret Street, Sydney, NSW 2000, AU)
Download PDF:
Claims:
THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:
1. A process for preparing a soluble conductive polymer comprising the step of electrochemically polymerising a monomer and/or an oligomer, or two or more different monomers and/or oligomers, or derivatives thereof in an electrolytic cell comprising monomer and/or oligomer solution, an electrolyte and an electrode assembly, wherein the monomer and/or oligomer solution is in a hydrodynamic relationship with respect to said electrode assembly.
2. A process according to claim 1, wherein the polymer is substantially fully soluble in an aqueous solvent.
3. A process according to claim 1 or claim 2, wherein the polymer is a homopolymer.
4. A process according to claim 1 or claim 2, wherein the polymer is a copolymer.
5. A process according to any one of the preceding claims, wherein a monomer and/or an oligomer, or two or more different monomers and/or oligomers, or their derivatives, are soluble in an aqueous solvent.
6. A process according to any one of the preceding claims, wherein the monomer or two or more different monomers, or their derivatives, are selected from the group consisting of, pyrrole, thiophene, aniline, 3alkysulfonate substituted pyrrole/thiophene, 3carboxyl substitute pyrrole, sulfonated anilines and their derivatives.
7. A process according to claim 6, wherein the monomer or two or more different monomers, or their derivatives, are selected from the group consisting of pyrrole (Py), 2 aminobenzene sulfonic acid (ASA), 3methoxyaniline5sulfonic acid (MSA), 2 methoxyaniline 5 sulfonic acid (2MSA) and [4(3 pyrrolyl)]butanesulfonate (PyB S).
8. A process according to any one of the preceding claims, wherein the monomer and/or oligomer solution further comprises a polyelectrolyte.
9. A process according to claim 8, wherein the polyelectrolyte is selected from the group comprising polyvinyl sulphonate (PVS), dextran sulphate, chondroitin sulphate, polyglutamic acid, polyacrylic acid, heparin sulphate and an electronically conducting polyelectrolyte.
10. A process according to any one of the preceding claims, further comprising a polymeric dopant to enhance solubility of the polymer.
11. A process according to any one of the preceding claims, wherein the electrolytic cell is of the flowthrough type.
12. A process according to any one of claims 1 to 10, wherein the electrolytic cell is of the stationary type.
13. A process according to any one of the preceding claims, wherein the electrode assembly comprises a working electrode and a counter electrode.
14. A process according to claim 13, wherein the working electrode is an anode.
15. A process according to claim 13 or claim 14, wherein the electrode assembly further comprises a reference electrode.
16. A process according to any one of claims 13 to 15, wherein the working and/or the counter electrode is in a microarray configuration.
17. A process according to any one of claims 13 to 16, wherein the working and/or the counter electrode is modified with a coating of a compound.
18. A process according to claim 17, wherein the compound induces electrocatalytic effects.
19. A process according to claim 18, wherein the compound is a polymer.
20. A process according to claim 19, wherein the polymer is polyaniline.
21. A process according to any one of claims 17 to 20, wherein the compound prevents deposition of the polymer on the electrode assembly.
22. A process according to any one of the preceding claims, wherein the hydrodynamic relationship is established by way of flow of monomer and/or oligomer solution past the electrode assembly.
23. A process according to any one of the preceding claims, wherein the hydrodynamic relationship is established by way of agitation of the monomer and/or oligomer solution.
24. A process according to any one of the preceding claims, wherein the hydrodynamic relationship is established by way of an electrode assembly which is moveable with respect to the monomer and/or oligomer solution.
25. A process according to claim 24, wherein the moveable electrode assembly comprises a rotating working electrode.
26. A process according to claim 25, wherein the rotating working electrode has a rotation rate of 0 to about 400 rev. min.~l.
27. A process according to claim 26, wherein the rotation rate is 0 to about 100 rev. mm.
28. A process according to any one of the preceding claims, wherein the monomer solution comprises NaNO3, pTS, NH40H, NaOH, pyridine, KCl or water.
29. A process according to any one of the preceding claims, wherein the electrolyte comprises NaNO3, pTS, NH40H, NaOH, pyridine, KCl or water.
30. A process according to any one of claims 11 to 29, wherein a flow rate of the monomer and/or oligomer solution in the flowthrough type cell is about 30mL/min to about 120 mL/min.
31. A process according to claim 30, wherein the flow rate is about 90 mL/min.
32. A process according to claim 30, wherein the flow rate is about 20 mL/min.
33. A process according to any one of claims 30 to 32, wherein the flow of the monomer and/or oligomer solution is a pulsed flow.
34. A process according to any one of the preceding claims, wherein a potential of +0.65V to +0.95V is applied.
35. A process according to claim 34, wherein the applied potential is +0.75V.
36. A process according to claim 34, wherein the applied potential is +0.50V.
37. A process according to any one of claims 34 to 36, wherein the potential is applied as a pulsed potential.
38. A process according to any one of the preceding claims, wherein the monomer and/or oligomer concentration is about 0.05M to about 0.15M.
39. A process according to claim 38, wherein the monomer and/or oligomer concentration is 0.010M.
40. A process according to any one of the preceding claims, further comprising a supporting electrolyte.
41. A process according to claim 40, wherein the supporting electrolyte comprises NaNO3, pTS, NH40H, NaOH, pyridine, KCl or water.
42. A process according to any one of the preceding claims, wherein the polymerisation is conducted over a time period of about 15 minutes to 30 hours.
43. A process according to claim 42, wherein the time period is about 90 minutes.
44. A process according to claim 42, wherein the time period is about 75 minutes.
45. A process according to any one of the preceding claims, wherein the monomer and/or oligomer solution comprises at least two different monomers and/or oligomers, or derivatives thereof.
46. A process according to claim 45, wherein the two different monomers and/or oligomers are present in a ratio of about 1:1 to 1:10.
47. A process according to claim 45, wherein the two different monomers and/or oligomers are present in a ratio of about 1:9.
48. A soluble conductive polymer produced by a process according to any one of claims 1 to 47.
49. A soluble conductive polymer according to claim 48, wherein the polymer is a homopolymer or a copolymer.
50. A soluble conductive polymer according to claim 48 or claim 49, wherein the polymer is soluble in an aqueous solvent.
51. Electrochemical cell for hydrodynamic electrochemical processing of conductive polymers comprising a first compartment having a working electrode and a second compartment having a first counter electrode, wherein the first and second compartments are separated by an ion exchange membrane and wherein the first compartment comprises means for establishing a hydrodynamic relationship between said working electrode and a monomer and/or oligomer solution when introduced into said first compartment, and comprising means for controlling applied potential and/or applied current and the degree of hydrodynamic relationship.
52. Electrochemical cell according to claim 51, which is a static electrolytic cell.
53. Electrochemical cell according to claim 52, wherein the means for establishing a hydrodynamic relationship is a working electrode which is movable with respect to its position within the monomer and/or oligomer solution.
54. Electrochemical cell according to claim 53, wherein the working electrode is capable of continuous rotation about its longitudinal axis.
55. Electrochemical cell according to claim 53, wherein the working electrode is capable of continuous movement in a vertical plane.
56. Electrochemical cell according to claim 53, wherein the working electrode is capable of continuous vibration.
57. Electrochemical cell according to any one of claims 51 to 56, further comprising inlet and outlet ports in at least the first compartment.
58. Electrochemical cell according to claim 57, which is a flowthrough electrolytic cell.
59. Electrochemical cell according to claim 57 or claim 58, wherein the means for establishing a hydrodynamic relationship is a flow of monomer and/or oligomer solution past the working electrode.
60. Electrochemical cell according to any one of claims 57 to 59, wherein a monomer solution is capable of flowing from the inlet to the outlet port past the working electrode.
61. Electrochemical cell according to any one of claims 51 to 60, further comprising a reference electrode.
62. Electrochemical cell according to claim 61, wherein the reference electrode is Ag/AgCl.
63. Electrochemical cell according to any one of claims 51 to 62, further comprising a third compartment and a second counter electrode, wherein the third compartment is separated from the first compartment by an ion exchange membrane.
64. Electrochemical cell according to claim 63, wherein the first and second counter electrodes are the same.
65. Electrochemical cell according to any one of claims 51 to 64, wherein the ion exchange membrane is lined on the side facing the first and/or the third compartment with filter paper.
66. Electrochemical cell according to any one of claims 51 to 65, wherein the working electrode is composed of reticulated vitreous carbon.
67. Electrochemical cell according to any one of claims 51 to 66, wherein the first and/or the second counter electrodes are composed of reticulated vitreous carbon.
68. Electrochemical cell according to claim 66 or claim 67, wherein the reticulated vitreous carbon has a porosity of 100 pores per inch (PPI) and a surface area of 65.6 cm2/cm3.
69. Electrochemical cell according to any one of claims 51 to 65, wherein the first and/or the second counter electrodes are composed of platinum.
70. Electrochemical cell according to any one of claims 51 to 69, wherein the working electrode and/or the first and second counter electrodes are in the form of a microarray electrode.
71. Electrochemical cell according to any one of claims 51 to 70, wherein the working electrode and/or the first or the second counter electrodes are selected from the group comprising porous metal, sinterred ceramic and conducting cloth electrodes.
72. An apparatus for hydrodynamic electrochemical processing of soluble conductive polymers comprising two or more electrochemical cells according to any one of claims 51 to 70, coupled into an assembly.
73. An apparatus according to claim 72, wherein each of the cells within the assembly is capable of being controlled separately with respect to applied potential, applied current, temperature and/or the hydrodynamic relationship between the working electrode and a monomer and/or oligomer solution when introduced into the first compartment.
Description:
TITLE: "HYDRODYNAMIC ELECTROPROCESSING OF SOLUBLE CONDUCTING POLYMERS" TECHNICAL FIELD The present invention relates to hydrodynamic processes for electrochemical production of soluble conductive polymers and to electroconductive polymers produced by such processes. The invention also relates to apparatus used for electrochemical production of soluble conductive polymers.

BACKGROUND ART The use of electrochemical methods to produce conducting electroactive polymers such as polypyrroles, polythiophenes and polyanilines (I-III shown below) has been shown to have significant benefits over the chemical oxidation approach.

Some particularly notable advantages are the following: A greater range of counterions can be incorporated. The only requirement is that the counterion salt (X+A-) be sufficiently conductive to sustain the polymerisation current.

. The energy input for the reaction can be controlled as a function of time. For example, it has been shown that the use of pulsed potential polymerisations induces unique properties in the resultant conducting polymer material. Others interested in the formation of polyanilines have demonstrated that optimal results are obtained when the potential of polymerisation is adjusted in-situ.

In general electroplating processes are employed since most conducting polymers are insoluble in common solvents. The limitation of this approach is that invariably heterogeneous structures are obtained. The morphology and composition near the electrode differ from those at the polymer solution interface and this inevitably leads to differences in chemical and physical properties eg. different contact angle measurements.

However the use of electrochemical processing need not be limited to the production of

insoluble conducting polymers. The same advantages discussed above are applicable in production of soluble materials, electrochemically.

Conducting polymers can be rendered soluble by the attachment of appropriate functional groups to the monomer prior to polymerisation. Interestingly the use of electrochemical methods to produce such soluble polymers has been limited.

It has been described recently how electropolymerisation can be used to produce organic solvent soluble conducting polymers based on alkyl pyrroles. Using the electropolymerisation method insoluble product was "filtered/collected" from the reaction via precipitation on to the electrode. The resulting product in solution was then highly soluble (some > 50% w/w). However, it was found that the elemental composition of the deposited polymers and that formed in solution varied markedly depending on the electrosynthesis conditions used.

It is an object of the present invention to overcome or at least ameliorate some of the disadvantages of the prior art.

SUMMARY OF THE INVENTION It has now been found that electrochemical processing of conducting polymers under hydrodynamic conditions can provide the synthetic flexibility required to produce soluble processable electro-functional polymers with tailorable properties. This technique permits the use of a wider range of dopant molecules (A-) which can impart special properties to the final product such as corrosion inhibition, conductivity, enhanced solubility and bioactivity. Thus, this technique also permits the production of polymers soluble in aqueous solvents, either by inclusion of dopant molecules or by way of polymerising suitably derivatised monomers and/or oligomers.

The large scale production of these polymers will also limit performance variation as the final commercial product would be produced from a common source rather than being synthesised as an individual product eg membrane, coating, sensor element and micro arrays.

The term "comprising" as used in the context of the present invention is used in an inclusive sense, that is to say in the sense of "including" or "containing". The term is not intended in an exclusive sense (ie. "consisting of' or "composed of').

The term "static cell" is used in the context of the present invention to differentiate a flowthrough cell arrangement from a cell in which the electrolyte and/or

monomer solution does not flow in and out of the compartments of the electrolytic cell.

This term does not refer to a static relationship between the ellectrode assembly and the electrolyte and/or monomer solution.

The term "hydrodynamic relationship" as used in the context of the present invention indicates that movement of electrolyte and/or monomer solution with respect to the electrode assembly takes place and includes situations where the movement is induced in the electrolyte and/or monomer solution alone as well as situations where the movement is induced in the electrode assembly. It would be clear to one skilled in the art that both the electrolyte/monomer solution and and the electrode assembly may be induced to move at the same time or intermittently.

According to a first aspect the present invention consists in a process for preparing a soluble conductive polymer comprising the step of electrochemically polymerising a monomer and/or an oligomer, or two or more different monomers and/or oligomers, or derivatives thereof, in an electrolytic cell comprising monomer and/or oligomer solution, an electrolyte and an electrode assembly, wherein the monomer and/or oligomer solution is in a hydrodynamic relationship with respect to said electrode assembly.

Typical monomers include 3-alkylsulfonate substituted pyrrole / thiophene, 3- carboxyl substituted pyrrole, sulfonated anilines and their derivatives. The majority of polymers arising from such monomers are self doped and typically have electrical conductivities lower than their unsubstituted forms. Unsubstituted monomers such as pyrrole, thiophene or aniline may also be used in the process of the present invention. The resultant polymer may thus be a co-polymer of self-doped and unsubstituted monomers.

Homopolymers or co-polymers containing unsubstituted monomers or oligomers may also incorporate other counterions, such as one or more high molecular weight/high charge density polyelectrolytes, achieving or enhancing solubility. Examples of suitable polyelectrolytes are polyvinyl sulphonate (PVS), dextran sulphate, chondroitin sulphate, polyglutamic acid, polyacrylic acid or heparin sulphate. Electronically conducting polyelectrolytes such as poly(methoxyanilinesulfonic acid) may also be incorporated as the dopant with unsubstituted homopolymers or co-polymers. Oligomers may be suitably employed in place of monomers.

Preferrably, the polymer obtained is soluble in an aqueous solvent but solubility in other solvents is also contemplated and can be easily achieved by using either suitably derivatised monomers or suitable dopant compounds mentioned above.

Electrochemical, rather than chemical. processing of these materials is preferable.

Preferably, the monomers used in the process are derivatised with sulfonic acid, for example 2-aminobenzene sulfonic acid (ASA), 3-methoxyaniline-5-sulfonic acid (MSA), 2- methoxyaniline-5 -sulfonic acid (2-MAS) and [4-(3 -pyrrolyl)]butanesulfonate (PyBS), however other monomers and/or oligomers can also be used in the process of the present invention. A mixture of more than one type of derivatised monomer may also be used in a co-polymerisation process. A monomer however need not be derivatised in order to be useful in the production of a soluble conductive polymer according to the process of the present invention. Different levels of solubility may be achieved by using mixtures of derivatised and non-derivatised monomers, as discussed above. Solubility may also be achieved using conventional polymers and high molecular weight/high charge density polyelectrolytes in a flow through cell arrangement.

Electropolymerisation of the monomers can be achieved under constant current or constant potential conditions. Benefits can also be achieved if pulsed current or pulsed potential are employed.

In a preferred embodiment the hydrodynamic relationship between the electrolyte and the electrode assembly results from the provision of an electrode which is movable with respect to the electrolyte and/or monomer solution. For example, the electrode may be able to rotate about its longitudinal axis, move from side to side or move up and down.

Alternatively. in a more preferred embodiment, the hydrodynamic relationship is achieved by providing a circulating electrolyte and/or monomer solution, for example in a flow through cell. An electrolytic cell of this type may have inlet and outlet ports arranged such that the monomer and/or oligomer solution flows past the electrode assembly. In such a process the electrode assembly may comprise a movable or a static electrode.

In yet another preferred embodiment the hydrodynamic relationship between the electrolyte and the electrode assembly is such that the electrode remains substantially

free of polymer deposition and the newly formed conductive polymer is substantially all in solution. The movement of electrolyte and/or monomer solution relative to an electrode can also be achieved in a number of different ways, all of which would be clear to a skilled addressee.

According to a second aspect the present invention consists in a soluble conductive polymer produced by a process according to the first aspect.

The conductive polymer obtained in the process of the present invention may be a homopolymer or a co-polymer and is preferrably soluble in an aqueous solvent.

According to a third aspect the present invention consists in an electrochemical cell for hydrodynamic electrochemical processing of conductive polymers comprising a first compartment having a working electrode and a second compartment having a first counter electrode, wherein the first and second compartments are separated by an ion exchange membrane and wherein the first compartment comprises means for establishing a hydrodynamic relationship between said working electrode and a monomer and/or oligomer solution when introduced into said first compartment, and comprising means for controlling applied potential and/or applied currentand and the degree of hydrodynamic relationship.

Preferably, the apparatus is a flow through cell, although a static cell having means of inducing movement of the electrolyte and/or monomer solution with respect to the electrode assembly is also contemplated. Thus a static cell may have an electrode assembly in which one or more electrodes is movable with respect to the monomer and/or oligomer solution, thus creating the hydrodynamic relationship between an electrode and the monomer and/or oligomer solution. Alternatively, a static cell having a fixed electrode assembly may have means for stirring the electrolyte, thus providing the required hydrodynamic relationship. Also preferred is a three-electrode cell comprising a working electrode, a counter electrode and a reference electrode. Microarray electrode configurations for any of the abovementioned electrodes are also suitable for use in the present process and can be produced in a flow-by or flow-through form.

The apparatus suitable for use in the present invention may be configured by assembling in parallel or in series more than one cell as described above. Each cell in

the assembly may be controlled separately or the entire assembly may be controlled centrally. Further, the cells arranged in series may have the electrolyte flow controlled such that at appropriate times it flows from for example one rotated/vibrating electrode cell or one flowthrough cell to another.

In any of the above described electrochemical cell configurations, modifying or pre-coating electrodes with, for example, polyaniline, prevents deposition of for example polypyrrole during its synthesis. Appropriate coating/modifiers could also be used to induce electrocatalytic effects. It is well known that polymers containing redox centres such as ferrocene (Lee, C. et al. Synth. Met. 1993, 55-57, 119-1122) metal complexes (Rohde, E. et al. Anal. Chim. Acta. 1983, 278, 5) or even conducting polymers (Kost, K.M. et al. Anal. Chem. 1988, 60, 2379) themselves can exhibit electrocatalytic effects, reducing the potential required to induce particular processes. In the context of the present invention such a reduction in potential can increase cell efficiency as well as decreasing polymer deposition on the working electrode.

According to a fourth aspect the present invention consists in an apparatus for hydrodynamic electrochemical processing of soluble conductive polymers comprising two or more electrochemical cells according to the third aspect, coupled into an assembly.

Preferably each cell within the assembly can be controlled separately with respect to applied potential, applied current, temperature and/or the hydrodynamic relationship between the working electrode and a monomer and/or oligomer solution when introduced into the first compartment.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an example of one type of flow through cell configuration which can be used for electroprocessing of conductive polymers.

Figure 2 is cyclic voltammograms obtained at a Pt disc electrode in 0.5M NaOH (a) and then addition of 0.5M ASA(b), 0.5M MSA (c), 0.25M ASA + 0.25M MSA (d).

Scan rate: 50mV/s.

Figure 3 is UV-vis spectra of polymerisation samples obtained from a flow- through cell at the polymerisation times of 0 min (a), 15 min (b), 30 min (c), 60 min (d), 120 min (e), 180 min (f), 240 min (g) and 300 min (h) respectively. Polymerisation solution: 0.5M ASA in 0.5M NaOH. Applied potential: +1.00V. Flow rate: 100ml/min.

Figure 4 is UV-vis spectra of polymerisation samples obtained from a flow- through cell at the polymerisation times of 0 min (a), 15 min (b), 30 min(c), 60 min (d), 120 min (e), 180 min (f), 240 min (g) and 300 min (h) respectively. Polymerisation solution: 0.5M MSA in 0.5M NaOH. Applied potential: +1.00V. Flow rate: 100ml/min.

Figure 5 is UV-vis spectra of polymerisation samples obtained from a flow- through cell at the polymerisation times of 0 min (a), 15 min (b), 30 min (c), 60 min (d), 120 min (e), 180 min (t), 240 min (g) and 300 min (h) respectively. Polymerisation solution: 0.25M ASA and 0.25M MSA in 0.5M NaOH. Applied potential: +1.00V.

Flow rate: 100ml/min.

Figure 6 shows a side view of another example of a flow-through cell configuration.

Figure 7 shows a microarray-type electrode configuration for either flow-by or flow-through applications.

Figure 8 shows an example of a static cell which makes use of a moveable (rotatable) working electrode (anode).

DESCRIPTION OF THE PREFERRED EMBODIMENT Novel concepts have been devised that improve the processing of soluble conducting polymers. One aspect of the invention makes use of flow through electrochemical cells, an example of which is depicted in Figure 1.

Another example of a suitable configuration of a flow through cell is shown in Figure 6. This type of set up is particularly preferred as it enables the electrode contact time and hence polymerisation time to be accurately controlled. The potential can still be controlled in-situ (eg. pulsed potentials) and the use of a segmented reactor enables staged control as a function of polymerisation time, as shown in Schematic 1 below. The use of a flow through segmented reactor also enables samples to be drawn off at different points in the polymerisation and/or products added. In addition, gradient mixing of reagents at any stage with a mixing profile that varies throughout the polymerisation, is possible. Cell design can also include temperature control, make use of pulsed flow and include control for flow rate and feed gradients to optimise the process. The nature and choice of such control systems would be clear to persons skilled in the art.

Schematic 1: Samples off - for Analyses and Characterisation Feed 1 Feed 2 Cell2 Feed 3 t E / E2 / E3 Feed 4 Feed 5 eg. Feed 1. Monomer Feed 2. Supporting electrolyte Feed 3.Buffer Feed 4. Optional Feed 5. Optional In a preferred embodiment, independent potential control can be applied on each cell. The feed compositions may also be pre-programmed and the flow rate may be variable throughout the process.

Microarray electrode configurations are also suitable for use in the present process (Figure 7). These electrodes can be produced in a flow-by or flow-through form.

This can be achieved by putting a porous electrode such as reticulated vitreous carbon, in a resin. The spectrode can then be polished back.

The process of the present invention need not only rely on the use of a flowthrough cell. Other means of providing a hydrodynamic relationship between the working electrode and the monomer/oligomer solution can be used. For example. a stationary cell may be employed in which the working electrode is be moveable by rotation, vibration or movement along the vertical axis. Figure 8 shows an example of a rotating electrode assembly comprising within the cell receptacle (1) a rotatable anode (2) and a pair of stationary anodes (3). The moveable electrode may be a disc, a flat plate, a ring or other configuration and may be porous or non-porous. An example of a suitable electrode is platinum disc or a platinum ring electrode. Other materials well known in the art may also be suitably employed, for example porous metals, sinterred ceramics, conducting cloths and similar materials.

Conducting polymers, which can be prepared by the hydrodynamic process according to the present invention, can be rendered soluble by the attachment of appropriate functional groups to the monomer prior to polymerisation. Examples of such monomers are given below.

The invention will now be more particularly described by way of example only with reference to figures and specific embodiments.

EXAMPLES Instrumentation Electrochemical experiments were carried out in an electrochemical cell preferably of the type and configuration shown in Figures 1 or 6 and preferably was a three-electrode system.

Referring to Figure 1, which shows an example of a suitable flow through cell, a typical configuration consists of a first compartment (1) which contains a working electrode (3) and a second compartment (2) which contains an auxiliary or counter electrode (4). The two compartments are separated by a membrane (5), typically an ion- exchange membrane, to prevent mixing of fluids between the compartments. Either one or both of the compartments can have inlet (6, 8) and outlet (7, 9) ports to allow flow through of either electrolyte (ports 8 and 9) or monomer solution (ports 6 and 7). The electrodes are connected to a source of current and a controller via electrode connections (11).

Another suitable electrochemical cell is shown in Figure 6. This type of configuration comprises a first inner compartment (12) having a working (anode) electrode (14) and two additional outer compartments (13) each having a counter (cathode) electrode (15). The inner compartment is sandwiched between the other two outer compartments and separated from them by ion-exchange membranes (19). Filter paper (20) may also be interposed between the membranes and each of the two outer compartments. The electrodes are equipped with connections (16) to allow application of potential and control. The inner and/or outer compartments may also have inlet (17) and outlet (18) ports to allow circulation and flow through of electrolyte and/or monomer solution.

In the flow through cell, the working electrode and auxiliary electrode are preferably reticulated vitreous carbon.

A reference electrode (10) may be employed, typically a Ag/AgCl (3M Nail) electrode.

Electrochemical control was achieved using a Bioanalytical System (BAS) model CV-27, EG & G Princeton Applied Research (PAR) bi-potentiostat model 366 or potentiostat/galvanostat model 363 controlled by a MacLab with an Apple Macintosh computer. UV-vis spectra were obtained using a Shimadzu UV-VISIBLE spectrophotometer model UV-1601. IR spectra were obtained using a Michelson spectrometer model MB 154.

I. Preliminary Studies Example 1: Electrochemical properties of monomers in stationary cell Since the monomers used have good solubility in base, the electrochemical properties were initially investigated in aqueous NaOH using cyclic voltammetry. The cyclic voltammograms of monomers in 0.5M NaOH were obtained (Fig. 2). For ASA, no polymerisation current was observed below +0.80V. As the upper potential became more positive, brown coloured polymer was observed around the working electrode.

The oxidation peak was obtained at +1.40V. MSA can be oxidised more easily. The oxidation started at +0.50V and oxidation peaks appeared at +0.80V and +1.20V.

The possibility of copolymerisation was then considered by recording cyclic voltammograms in a solution containing a mixture of the t-wo monomers (MSA/ASA 1:1). Oxidation was observed at +0.55V and oxidation peaks appeared at +0.95V and +1.40V.

In order to deposit polymer on the working electrode, three methods (ie.potentiodynamic, potentiostatic and galvanostatic) have been investigated.

Using the ASA Monomer . Keeping the initial potential at -0.2V, cyclic voltammograms were run to different upper potential limits (between +0.80V and +2.00V) in the polymerisation solution for 20 cycles. No polymer deposition could be obtained.

. For ASA, potentiostatic polymerisation was investigated at +0.80V and +1 .00V respectively. At +0.80V, no polymerisation was observed, the current generated was very small. At E>+1.00V, ASA can be oxidised, the polymer formed was brown.

However, polymer deposition on the electrode was not observed.

. Galvanostatic polymerisation did not produce any polymer deposit on the electrode even when high current densities (1 0mA/cm2) were employed. The increase in potential at longer times is presumably due to depletion of the monomer.

;i Using the MSA Monomer No deposit was observed with cyclic voltammetry.

. Potentiostatically, polymer deposition was observed at Eapp = +0.80V and +1.00V.

However, at higher potentials, such as +1.50V, no electroactive polymer was deposited presumably due to polymer overoxidation.

. Application of a constant current, also resulted in oxidation of MSA. Using a low current density (2mA/cm2), the polymer produced was in solution, no polymer deposition was observed on the electrode. Using high current density, such as 1 0mA/cm2, a potential drop was observed indicating that polymer was deposited at the electrode surface.

The electrochemical behaviour of the monomers in other bases (NH40H and pyridine), neutral supporting electrolyte KCl and even without any supporting electrolyte has also been studied. Both monomers can be oxidised in all environments employed.

The oxidation potentials are summarised in Table 1.

Table 1 Oxidation peak potentials of monomers obtained in a range of supporting electrolytes. Supporting electrolyte Monomer NaOH NH40H Pyridine KCI H2O ASA +1.42 +1.34 +1.60 +1.10 +1.25 MSA +0.80, +1.20 +0.78, +1.14 +1.23, +1.56 +0.93, +1.42 +1.16 ASA/MSA +0.94,+1.40 +0.83, +1.36 +1.60 +0.93, +1.06 +0.95, +1.23 Conditions: monomer concentration = 0.5M (for ASA/MSA: 0.25M ASA + 0.25M MSA) in 0.5M NaOH, NH40H or pyridine; 0.1M (for ASA/MSA: 0.05M ASA + 0.05M MSA) in water or 0.1M KCl.

Example 2: Electrochemical polymerisation of MSA at a rotating electrode Since P(MSA) was deposited on the electrode surface, polymerisation at rotating electrodes was also investigated to determine the effect of hydrodynamic control.

Chronoamperograms obtained using potentiostatic polymerisation (E=+1.OV) were monitored. It was found that, as the rotation rate increased, the current decreased markedly (Table 2). At rotation rates above 400 rev min-1, polymer cannot be deposited.

Table 2 Effect of rotation rate on the deposition current of 3-Methoxyaniline-5-Sulfonic acid (MSA) under constant applied potential. Rotation rate (rev. min-1) 0 50 100 200 400 Current (mA) 12.10 11.20 9.10 2.50 0.25 Conditions: applied potential = +1.00V, 0.5M MSA in 0.5M NaOH.

Using constant current polymerisation at rotation rates below 50 rev min-1, a potential drop was always observed which indicates the deposition of polymer onto the electrode surface. At rotation rates above 70 rev min-1, no potential drop was found and no polymer deposition can be obtained. The polymerisation/deposition potential increased when the rotation rate increased (Table 3).

Table 3 Effect of rotation rate on the deposition potential of 3-Methoxyaniline-5- Sulfonic acid (MSA) under constant applied current. Rotation rate (rev min-1) | 0 | 10 I 20 30 50 70 j00 Potential (V) 0.51 1 0.5 0.52 iw$½¼0.55 1 0.83 1 0.87

Conditions: current density = 10 mA/cm2, 0.5M MSA in 0.5M NaOH.

Example 3: Electrochemical synthesis of sulfonated polyaniline using a flow- through system Electrochemical polymerisations of ASA, MSA, and ASA/MSA using the flow- through system was investigated using 0.5M NaOH and potentiostatically at E=+1 .00V.

At this potential, monomer can be oxidised while the overoxidation of polymer can be minimised. The flow rate used was 100ml/min. Samples were taken at different polymerisation times for UV-vis investigations. Compared with the samples before polymerisation, all polymerised samples showed UV-vis bands, which increased as the polymerisation time increased indicating polymer has been produced (Fig. 3-5).

After five hours, the polymerised solution was collected and poured into acetone.

The precipitate was collected on a kiriyama funnel using a water aspirator. The precipitate was washed with 100ml MeOH and then dried for 12 hours at 60 OC. The yield and electrical efficiency for three polymers were estimated and summarised in Table 4. The obtained polymers were characterised using UV-vis and IR and were as expected.

Table 4 Yield and electrical efficiency of electrochemical synthesis of sulfonated polyaniline. Polymer Yield Poly (ASA) 43.0% Poly (MSA) 39.8% Poly (ASA/MSA) 21.7% Conditions: applied potential = +1 .00V; monomer concentration = 0.5M (for ASA/MSA: 0.25M ASA + 0.25M MSA) in 0.5M NaOH. Flow rate: 100ml/min.

Polymerisation time = 5 hours.

Example 4: Characterisation of Conductive Polymers Using 80% water containing 0.2M NaNO3, 0.01M Na2HPO4, pH=9 and 20% methanol as eluent and using polyethylene glycol as calibrant, gel permeation chromatography (GPC) was carried out on samples obtained from flow cell experiments. These preliminary results (Table 5) indicate that only a small percentage (about 10%) of material has a high molecular weight. This may be related to the low

electrolyte cell efficiency under the conditions employed, the cell configuration, the arbitrary flow rate chosen and/or the composition of the feed solution. Despite these limitations, of particular interest is the ability to make the copolymer with low polydispersity.

Table 5 GPC data (molecular weight) for sulfonated polyanilines. Polymer M Mn Mw polydispersity Poly(ASA) 1466 1512 8272 5.470 Poly(MSA) 1446 834 8478 10.154 Poly(ASA/MSA) 1013 796 1300 1.634 Conditions: Eluent: 80% 0.2M NaNO3, 0.01M Na2HPO4, pH 9, 20% methanol. Flow rate: 1.0 ml/min. Calibrants: polyethylene glycol. Polymer sample concentration: 3 mg/ml in eluent. Mn = number average molecular weight; Mw = weight average molecular weight; Example 5: Electrochemical synthesis of poly (MSA) in different solvents Electrochemical synthesis of poly (3-methoxyaniline- 5-sulfonic acid), abbreviated as P(MSA), has been carried out in a range of different solvents including H2O, KCl, NH40H and pyridine. Electrochemical synthesis was monitored by taking UV spectra of samples at different polymerisation times. Molecular weights were obtained using gel permeation chromatography (GPC).

Electrochemical synthesis was performed using a flow cell consisting of a three- electrode system (Schematic 2 above). The anode and cathode components were separated by two membranes. Flow rate used was 40ml/min. The reference electrode employed was an Ag/AgCl (3M NaCl). Electrochemical control was achieved using EG & G Princeton Applied Research (PAR) potentiostat/galvanostat model 363 controlled by a MacLab interfaced with a Apple Macintosh computer. All polymerisation experiments were performed potentiostatically at +1 .OOV. UV-vis spectra were obtained using a Shimadzu UV-VISIBLE spectrophotometer model UV- 1601. GPC measurements were carried out by using a Waters M-6000A solvent devivery system, a PL Aquagel-OH=TSK Gel G3000PWXL columns. A Refractive Index Detector and a Rheodyne 7725 manual injector with the injection size of 200pal was employed. The data was collected with a PL Data Capture Unit (DCU), and analysed using PL Calibre version 6.0 GPC/SEC software. Data was collected at ipoint/sec. The eluent used was 80% 0.2M NaNO3, 0.05M Na2HPO4 (pH=9.0), 20% methanol with the flow rate of 1.0 ml/min. Polyethylene glycol was employed as calibrant.

The experimental conditions and results for each experiment are summarized in Table 6.

Table 6 Experimental conditions and results for P(MSA) Experiment Solvent Anode solution Cathode polymerisation yield number solution time (hrs) (%)(1) Nol H20 0.2M MSA in 0.5M KCI 8 51.3 H20 No2 KCI 0.2M MSA in 0.5M KCl 7 66.2 0.5MKC1 No3 pyridine 0.5M MSA in 0.5M KCl in 3* 18.0 0.5M pyridine 0.5M pyridine No4 NH40H 0.5M MSA in 0.5M NH40H 10 103.8 0.5M NH40H Legend: * = the generated polymer blocked the cell at polymerisation times around 3 hours. (1) = Calculated from mass of polymer precipitated from ethanol.

For each experiment the polymerisation solution (anode solution) was obtained by dissolving monomer MSA in the corresponding solvents. The cathode solution was solvent only except for where H20 and pyridine (non-electrolytes) were used. In these cases another electrolyte (KCl) was employed. Electrochemical synthesis was monitored by checking UV spectra of samples at different polymerisation times. It was assumed that the synthesis reaction was complete when the polymer UV absorbance reached a constant value. For the experiment in pyridine, the polymer generated precipitated in the course of the experiment. After about 3 hours the cell was blocked with polymer precipitate so that the experiment could not be continued.

To ensure the solubility of monomer (MSA), a basic ethanolic solution was used to precipitate the polymer. So a basic solution (0.2M NaOH) was used to adjust the pH of ethanol to 12. Addition of 5ml polymerisation solution to 250ml ethanol solution resulted in P(MSA) precipitation. After aging for 2 hours, the precipitate was collected on a kiriyama funnel using a water aspirator. The precipitate was washed with 100ml ethanol and then dried for 12 hours at 60"C. The yields for all experiments were estimated and summarised in Table 6 above.

Example 6: The measurement of molecular weight using GPC As described earlier, the molecular weights for all polymers obtained above were measured using GPC. As a comparison, molecular weight for the pre-precipitated polymer obtained in experiment No3 was measured as well. All results are summarized in Table 7. For electrosynthesis carried out in water or NH4 OH MWts of the order of 20,000 could be obtained. Electrosynthesis in KCl gave lower MWt but also lower polydispersity.

Table 7 GPC data (molecular weight) for P(MSA) obtained in a range of solvents. Number Solvent | Mp Mn Mw polydispersity Nol H20 4809 5531 25760 4.657 No2 KCl 5258 4030 5905 1.465 No3 NH40H 5400 4893 18050 3.688 Conditions: Eluent: 80% 0.2M NaNO3, 0.01M Na2HPO4, pH 9, 20% methanol. Flow rate: 1.0 ml/min. Calibrants: polyethylene glycol. Polymer sample concentration: 6 mg/ml in eluent.

II. Further studies Chemicals and reagents 2-Methoxyaniline sulfonic acid (2-MAS) was supplied by Nitto Chemical Industry Co., Ltd. HCl (32%), NaOH, NH40H (28% NH3 solution), and pyridine were used as received. The solvents used were of analytical grade. Water was deionised.

Electrochemical characteristics of 2-MAS in a stationarv cell The electrochemical characteristics of 2-MAS in a stationary cell were investigated in a three-electrode cell. The working electrode was a platinum disk of 0.05cm diameter. The auxiliary electrode was a platinum mesh and the reference electrode was Ag/AgCl (3M NaCl). Cyclic voltammograms and chronoamperograms were obtained by sweeping the potential or applying a constant potential with a Bioanalytical Systems (BAS) CV-27 Voltammograph which was interfaced with an ADInstruments/4e Maclab.

Flow Cell System The Flow Cell employed was designed by Intelligent Polymer Research Institute (IPRI). It is a three-electrode cell that consists of a working electrode and two auxiliary electrodes between which the working electrode is positioned. The working electrode

and the auxiliary electrodes were separated by a Nafion ion-exchange membrane, which was protected from polymer deposition by filter paper.

Polymerisation of 2-MAS in the Flow Cell System Polymerisation of 2-MAS was performed in the Flow Cell system.

The catholyte was NH40H solution, and the polymerisation solution was 2- MAS/NH4OH solution. The potential was applied using a Potentiostat/Galvanostat (a PAR Model 273A).

The electrochemical polymerisation process was monitored using HPLC and GPC as well as UV-visible (UV-vis) spectrophotometry.

HPLC was carried out using an Alltech Altima Cl 8U aniline specific column that was connected to a Dionex LC gradient pump set at a flow rate of 0.8ml/min with a LINEAR UV-vis 200 detector set at 236nm.

The distribution of polymer molecular weights in polymerisation samples was determined using a Gel Permeation Chromatography (GPC) set up. The GPC columns were Waters Ultrahydrogel 120 and 250, with a MWt range of 200 to 5000 and 1000 to 80000, respectively. The columns were connected to a Shimadzu (LC-1OAT) pump set at 0.6ml/min and kept at 350C. A LINEAR UV-vis 200 detector set at 254nm was employed, and was interfaced with a Shimadzu CBM- 1 OA Communications Bus Module. Data was recorded using an IBM computer with Shimadzu LC-10 (v1.2) software. Molecular weights were calculated using the Shimadzu GPC software for the LC-10 software. The calibrants were polystyrene sulphonate-sodium salt.

A Shimadzu 1601 UV-VIS spectrophotometer was used to monitor the polymerisation process.

Separation of polymer products The separation or recovery of polymer from the polymerisation solution was carried out by two different methods.

(a) Acetone Treatment The solution was added into acetone (polymerisation solution: acetone = 1:10) and the precipitate collected on a funnel and washed with acetone, and then dried.

(b) Dialysis

The polymer solution was dialysed against water using dialysis tubing. The polymer was recovered by evaporation using a rotary evaporator-and then dried.

Electrochemical properties The conductivity of polymers was measured using the ASTM four point probe technique. A Hewlett Packard 34401A Multimeter and a PAR 363 Potentiostat/Galvanostat were used for the conductivity measurement.

Example 7: Stationary Cell Voltammetry As discussed earlier, cyclic voltammetry (CV) of aniline during growth shows two pairs of distinct redox peaks that grow in magnitude as polymer is deposited.

However, the cyclic voltammogram of 2-MAS was different from that of aniline. Only one oxidation peak was observed at 1 .0V and no redox peaks were observed at more negative potentials. Furthermore, the response obtained did not grow on subsequent sweeps, indicating that no deposition occurred on the electrode and that the product was soluble in water. The hydrodynamic voltammogram obtained using the small platinum electrode was similar to the CV data.

Chronopotentiograms recorded during polymerisation showed that the observed potential increased as the applied current density was also incresased. Overoxidation of 2-MAS occurred when current densities greater than 0.8mA/cm² were employed. The electrochemical characteristics of 2-MAS in HCl solution were similar to those obtained in water. However two oxidation peaks (+0.88V and +1.30V) were observed. The hydrodynamic voltammogram suggests that overoxidation of 2-MAS occurred at potentials greater than 0.95V.

Cyclic voltammograms were obtained in three different basic solutions (sodium hydroxide, ammonium hydroxide, pyridine). They all exhibited an oxidation peak at about 1.or. The effect of the concentration of 2-MAS on the voltammetry was investigated. From chronoamperograms, it can be seen that increasing the concentrations of 2-MAS is advantageous. Markedly higher currents were observed for oxidation of 0.5M 2-MSA when NH40H was used as supporting electrolyte. This corresponds with the lower oxidation potential observed for 0.5M 2-MSA in NH40H.

Example 8: Electrochemical Polymerisation Of 2-MAS In A Flow Cell System Ammonium hydroxide (NH40H) was used as supporting electrolyte. The composition of the polymerisation solution was 0.5M 2-MAS/0.5M NH40H.

Hvdrodvnamic Voltammetry Of 2-MAS In The Flow Cell System Previous HDV's were recorded using a Pt disc electrode. Due to change of cell type, it was necessary to investigate the hydrodynamic voltammetry of 2-MAS in the RVC based Flow-Through System. The polymerisation current reached a limiting value at potentials > 0.90V.

Effect Of Reaction Time On The Electrochemical Polymerisation Of 2-MAS The conversion of 2-MAS (at +0.90V) as a function of reaction time was investigated using HPLC to determine residual monomer. After 22 hours, all MAS had been consumed.

Effect of potential on the polymerisation of 2-MAS The electrochemical polymerisation of 2-MAS was performed using different applied potentials in the Flow Cell System. The applied potential had a marked effect on the conversions of 2-MAS where at low applied potentials (e.g. 0.50V), the conversion per unit time of MAS was low. This conversion efficiency increased with application of more positive potentials. This result was consistent with the hydrodynamic voltammetry data obtained above. However, the applied potential also had an effect on the molecular weight of the polymer obtained. Under mild oxidation conditions (e.g. 0.50V), the maximum molecular weight of the polymer obtained was higher. From GPC data, it was confirmed that the low molecular weight fraction increased when polymerisation was carried out at higher potentials.

Example 9: Electrochemical Polymerisation Of 2-MAS At Low Potential As discussed above (see GPCs) the polymers obtained consist of both high and low molecular weight components. With an increase in potential, the low molecular weight component increased. Electrochemical polymerisation of 2-MAS at 0.5V was therefore studied.

Effect of Reaction Time on Molecular Weight of Polvmers at 0.5V GPC analyses were carried out to determine the MWt of polymers produced after different reaction times. Compared with previous experiments, the distribution of molecular weights was improved. With increased reaction time, the higher molecular weight fraction also increased, with values up to 22,000 being obtained. However, after 30 hours, the distribution moved towards lower molecular weights. After 47 hours reaction, the molecular weights decreased to 8128 and three peaks (degradation by- products) appeared on the GPC plot.

Effect of Flow Rate For processing soluble conductive polymers, flow rate is related to the contact time of the polymerisation solution with the electrodes, so it directly affects the polymerisation.

(i) Low Flow Rate (20ml/min) At low flow rate, the polymers obtained were mainly composed of the high molecular weight components. Molecular weights of these components increased up to 30 hours of synthesis. The highest molecular weight fraction obtained was 29,000.

(ii) High Flow Rate (1 00ml/min) The molecular weight of polymer product vs reaction time were studied. After 28 hours, the molecular weight of polymers began to decrease and the degradation of polymers was observed.

Comparsion of Different Flow Rates The molecular weight of the polymer products obtained decreased with increased flow rates, while the yield of polymers per unit time also decreased. Their distributions are different from each other, but it is clear a high flow rate may be disadvantageous to the polymerisation of 2-MAS. Conductivities of samples obtained at different flow rates are shown in Table 8.

Table 8: Conductivities of P(2-MAS) Obtained at 0.5V for 30 hours Conductivity (S/cm) No Samples* 2Omllmin 40ml/min 100ml/min 1 ~ P(2-MAS), by Acetone 6.2x10-3 5.9x10-3 4.3x10-3 2 P(2-MAS), HC1 Evapor 4.9x10-3 4.8x10-3 3 P(2-MAS), 1M HC1 2.2x10-2 6.8x10-3 5.1x10-3 4 P(2-MAS), by Dialysis 8.3x10-2 4.8x10-2 --

Example 10: Electro-synthesis of P(2-MAS) using stepped potential Experimental The flowthrough cell was used. An Ag/AgCl (3 M KCl) reference electrodewas employed. 2- MAS (10%) was adjusted with NH4 OH to a pH 4.4 - 4.5. Flow rate was set at 100 ml per minute. Applied potential was stepped down from El to E2 (i.e.

E1>E2). Operating temperature was 28-30"C.

P(2-MAS) SeParation P(2-MAS) solution o acetone precipitation < filtration o fridge drying e grinding < P(2-MAS) o pellet making.

Dialysis To prepare dialysed P(2-MAS), the a prepared P(2-MAS) solution was dialysed for 24 hours using a dialysis tubing with Mw cut off of 12,000. The dialysed solution was further concentrated by vacuume vaporisation and then followed by the above separation.

The electrical conductivity of the P(2-MAS) was also measured using standard condition as described previously. A P(2-MAS) pellet was made by usign 100 mg P(2- MAS) powder and pressed at 400-600 atm for 10 seconds using the Kbr pellett maker. A four probe conductivity measurement device was used in which only four small points were in contact with the sample. A more accurate measurement can be achieved with this technique. However, any commercially available sensitive conductivity measurement device can be employed.

Results UV-vis spectra of P(2-MAS) versus poymerisation time were obtained and these spectra were mainly used for monitoring the progress of the electropolymerisation process. Due to its well characterised absorption bands, the overoxidation of P(2-MAS) can also be found through the analysis of its UV-vis spectra.

In three different step-potential experiments, only slightly band shift (292 nm to >300 nm) was found. The band shift, to some extent, was caused by the overoxidation of P(2-MAS).

The GPC molecular weights were also obtained. The highest average molecular weight was obtained when El was +0.60V and E2 was +0.50 V. A conversion rate of 91 % was achieved within 20 hours of polymerisation.

The electrical conductivity of the P(2-MAS) was also measured before and after dialysis. It was found that the electrical conductivity can be increased by up to 70 times through dialysis. In addition, an electrical conductivity value of 0.70 S/cm has been achieved after dialysing the P(2-MAS). A variation in electrical conductivity between different experiment was found. This phenomenon is believed to be caused by the sample being chosen for the dialysis. Only those final P(2-MAS) products (solutions) were chosen and dialysed in this series of experiment.

Table 9 Result of varying the potential during a polymerisation run. Potential Profile Ave. Mwt/ Highest Mwt Conductivity as After dialysis prepared 0.6Vo0-13 hrs 10,959 24,021 0.08 0.20 0.5Vo13-18 hrs 0.7V 0-10 hrs 8,468 17,230 0.01 0.70 0.5V 11-29 hrs 0.7V 0-10 hrs 6,563 16,500 0.003 0.20 0.55V 11-20 hrs Example 11: Electropolymerisation of 2-MAS under selected constant potential conditions The EC synthesis was carried out using the IPRI cell. The IPRI cell consisted of three separate compartments, i.e. working electrode compartment and two counter electrode compartments. The electrode material used is RVC - a macro-porous carbon material with high effective surface area. A Ag/AgCl reference electrode was set up in the working electrode compartment in order to control the potential.

Electrochemical polymerisation was carried out at +0.50 V (vs Ag/AgCl) at a flow rate of 20 mL/min or 100 mL/min.

A light yellow coloured solution was observed after about 30 minutes of polymerisation. The solution was darker with increased polymerisation time.

The pH began to increase after 5 hours and was approximately 7 upon completion of the polymerisation.

Output Current Profile The change in the observed current is another indicator of 2-MAS polymerisation and is indicative of oxidative efficiency. The current was observed to be independent of flow rate.

Uv-Vis Srectrophotometry Study The UV-vis spectra of P(2-MAS) show two characteristic peaks (475 nm and 299 nm). The 299 nm peak is closely related to the MAS monomer concentration while the 475 nm peak is related to P(2-MAS) in the solution. It was found that the monomer concentration slowly decreased while the polymer concentration increased as a function of the time. No degradation in the electronic structure was observed over the first 24 hours of polymerisation. This observation was supported by the GPC profiles obtained as will be discussed later.

Gel Permeation Chromatography Analysis The molecular weight of the P(2-MAS) was analysed by GPC. All samples were diluted 10 times except the sample at 43 hours which was diluted forty times due to the higher concentration of polymer present.

The maximum molecular weight fraction as well as the average molecular weight increased for the first 26 hours and then decreased with further polymerisation, which might be an indicator of degradation of P(2-MAS). As indicated by the 43 hours sample, the monomer peak area was getting smaller and its concentration in solution about 5.5% by weight. This can also be roughly interpreted as 94.5 % of MAS has been converted into P(2-MAS).

In the initial stage, the average molecular weight was low. The average molecular weight was greater than 10,000 after 26 hours of polymerisation, with the high molecular weight fraction around 23,000. Further polymerisation increased the average molecular weight, but reduced the high molecular portion from 23,000 to 12,000. The molecular weight fraction distributions shows that after 26 hours the two major synthesis products were 41% 1,000-3,000 daltons and 53% greater than 10,000. After 46 hours of synthesis this improved to 16% 1,000-3,000 daltons and 80% > 10,000 daltons. When compared with GPC profiles of chemically prepared P(2-MAS), the chromatogram of electrochemically prepared P(2-MAS) after 43 hours was similar to that of chemically

Example 12: Electrosynthesis Of P(2-MAS) At +0.50 V And 20 MVMin Without Using The Anion-Exchange Membrane Experimental conditions: Polymerisation sol: 125 mL of 10% (w/w) 2-MAS monomer solution with its pH adjusted to pH 4.50 using 28% ammonia Polymerisation cell: IPRI small-scale cell with RVC electrode without membrane Flow rate: 20 mL per minute Potential applied (Eapp): 0.50 V vs Ag/AgCl (3M KCl) Results The UV-vis spectra shows no evidence of over-oxidation, and the P(2-MAS) concentration increased with the synthesis time.

The average molecular weight of P(2-MAS) was in the order of 10,100 in 21 hours excluding the remaining 2-MAS monomer from the average molecular weight calculation. In this case if higher conversion rates (such as that at higher polymerisation potential) can be obtained then the goal of an average molecular weight of over 10,000 can be achieved.

The electrical conductivity of the P(2-MAS) pellets was measured using the four- probe technique. The average conductivity was around 0.02 S/cm (TablelO).

Table 10: Comparison of the electrical conductivity of P(2-MAS) under different condition Experimental condition Electrical conductivity (S/cm) 0.5 V and 20 mL/min 0.02 0.5 V and 100 mL/min 0.02 0.5 V and 20 mL/min without membrane 0.02 0.6 V and 100 mL/min 0.01 0.65 V and 100 mL/min (dialysed) 0.2 *P(2-MAS) was separated using the acetone and then dried. P(2-MAS) pellets of 0.06 cm thickness were made using 100 mg of P(2-MAS) and pressed at 400 kg/cm2 for 10 seconds. Four-probe conductivity was measured with these P(2-MAS) pellets.

prepared P(2-MAS) but, the P(2-MAS) prepared electrochemically had a significantly higher upper molecular weight fraction.

At the higher flow rate, (100mL/min) the GPC chromatograms show a similar pattern to that obtained at lower flow rate. However, loss of the higher MWt fraction was not obvious at longer polymerisation times.

These values are higher than those obtained in previous experiments, including chemically prepared P(2-MAS).

Conversion Of 2-MAS The conversion of 2-MAS to P(2-MAS) was analysed with the HPLC. The conversion rate o: is expressed as <BR> <BR> <BR> C1<BR> <BR> of=(l- )x100% <BR> <BR> CO where the Co and Ct are the 2-MAS concentration at the time of 0 and t.

The conversion of 2-MAS to P(2-MAS) was dramatically affected by the hydrodynamic condition employed. Lower flow rate tends to result in high conversion rate. The conversion of 2-MAS at flow rate of 20 mL/min is around 75% and 96% after 24 hours and 48 hours respectively. While the conversion rate is only about 50 % at 100mL/min after 24 hours polymerisation. GPC plots revealed similar values for the conversion of the monomer 2-MAS, which might be used as an alternative method for conversion evaluation.

P(2-MAS) Separation And Conductivity Measurement The P(2-MAS) was separated by adding acetone in a ratio of 10:1. P(2-MAS) precipitates were formed when the 24 hour-polymerisation solution was added drop wise. The precipitates were filtered and freeze dried. The final product was similar to that prepared chemically.

P(2-MAS) pellet was made by pressing the 100 mg P(2-MAS) powder at 400- 600 Kg/cm2 for 10 seconds. The electrical conductivity of the P(2-MAS) (samples at 24 hours for both 20 and 100mL/min) was then measured with an average value around 0.02 S/cm.

Example 13: Characterisation of Poly(l4-(3-pyrrolyl)]butane sulfonate) Homopolymer Synthesis Points: Electrolyte Volume: 100 mL . Catholyte: 100 mL 0.2 M NaNO3 I. Materials Sodium PyBS 98%+ was synthesised at IPRI. Sodium nitrate 99% and methanol (HPLC grade) were obtained from BDH Chemicals. 4-Toluene sulfonic acid sodium salt 98%+ was supplied by Merck-Schuchardt Co. di-Sodium hydrogen orthophosphate anhydrous (AR grade) was from AJAX Chemicals. Tetrabutylammonium dihydrogenphosphate (1 M) was from Aldrich Chemical Co. All solutions were prepared with deionised Milli-Q water.

II. Electronolymerisation of P(PvBS! homopolymer P(PyBS) was synthesised electrochemically by flowing the anolyte solution through a electrochemical flowthrough cell, Figure 6. The cell consisted of an anode compartment filled with reticulated vitreous carbon (RVC). This anode was sandwiched between two RVC cathodes of similar dimensions and separated by anion exchange membrane (Neosepta) to prevent mixing between the anode and cathode compartments.

All electrode potentials were measured relative to a Ag/AgCl reference electrode.

Princeton Applied Research (PAR) model 363 and 273A Potentiostat/Galvanostat were used for the potentiostatic polymerisation. A MacLab interfaced with a Macintosh computer was employed for recording the PAR model 363 electropolymerisation data and a PC interface was used to record the PAR 273 electropolymerisation data.

A total synthesis time of 90 min has been used for each experiment with sampling intervals every 15 min for GPC, HPLC and UV-Vis determinations. Electrical conductivity and yield were measured for each soluble and deposit polymer fractions after dialysis (12,000 Dalton cut off) with water.

Characterisation of P(PVBS) GPC GPC was performed using a Shimadzu LC-1OAT Liquid Chromatograph system with Waters Ultrahydrogel 120 and 250 columns to determine the molecular weights of P(PyBS). The mobile phase consisted of 80% (0.2 M NaNo3(aq) and 0.01 M

Na2HPO4(aq)) + 20% Methanol. A flow rate of 0.8 mL/min. was used and absorbance was monitored at 254 nm with 50 pL injections of each -sample (1: 5 dilution). The soluble fractions and deposited fraction were all analysed by GPC.

HPLC Monomer conversion rate was measured by using a Waters 501 HPLC with a Alltima C18, 5 mm (250 x 4.6 mm) column. The mobile phase was 50% methanol/water (0.005 M tetrabutyl ammonium phosphate) at a flow rate of 0.6 ml/min. Soluble fraction samples with 1: 50 dilution were monitored at 236 nm with 50 pL injections.

UV-visible spectra A Shimadzu UV-visible Spectrophotometer UV-1601 was employed in this study. Soluble fraction samples with 1:20 or 1:40 dilutions were monitored at 300 to 1100nm.

Conductivity Testing The electrical conductivity of the P(PyBS) was determined using the four probe technique. The soluble and deposited samples were dialysed against water over night and dried down prior to testing the conductivity. The resulted polymer was then pressed to a pellet under 6 tons and its conductivity was measured.

Example 14: Optimisation of P(PyBS) Homopolymer Synthesis.

The optimisation of P(PyBS) homopolymer synthesis is shown below in Scheme 1. The optimisation process has been divided into four stages. For each experiment polymer yield, molecular weight (GPC), UV-vis spectra, monomer consumption (HPLC) and electrical conductivity was measured. A total synthesis time of 90 minutes was used for each experiment with sampling intervals every 15 min for GPC, HPLC and UV-vis determinations. Yield and electrical conductivity were determined after 90 minutes of synthesis and dialysis (12,000 Daltons cut off).

Stage 1 - Optimisation of flow rate.

Optimum flow rate were determined by varying the flow rate from 30 to 120 mL/min in 30 mL increments using 0.1 M PyBS, 0.2 M NaNO3 at 0.75 V.

Stage 2- Optimisation of Applied Potential.

Potentials from 0.55 to 0.95 V in 100 mV increments were investigated using 0.1 M PyBS, 0.2 M NaNO3 at the optimum flow rate (Stage 1)

Stage 3 - Optimisation of fPyBSj The effect of PyBS monomer concentration from 0.05 to 0.15 M was investigated using the optimum flow rate and potential (Stages 1 & 2) in the presence of 0.2 M NaNO3.

Stage 4 - Optimisation of Electrolyte Using the optimum conditions from stages 1 to 3 the synthesis electrolyte was changed from NaNO3 to either 0.2 M para-toluenesulfonate (p-TSNa) or none.

Scheme 2: P(PyBS) synthesis optimisation path.

(Note: Arrows indicate optimum condition to be used in following step.) Stage I Stage 2 Stage 3 Stage 4 Flow Eapp (V) PyBS (M) Electrolyte (mL/min) (M) 30 0.55 60 4 0.65 < 0.05 < 0.2M p-TSNa 90 0.75 0.10 none 120 0.85 0.15 0.95 Example 15: Homopolymer Optimisation: Stage 1 - Variation of Flow Rate.

The effect of flow rate on the conversion of the PyBS monomer to P(PyBS) from 30 to 120 mL/min was investigated using using both HPLC and GPC techniques, Figure 26, at 0.1 M PyBS, 0.2 M NaNO3 at a potential of+ 0.75 V vs Ag/AgCl. Flow rates at 90 and 120 mL/min were found to give better monomer conversion than the lower flow rates and had similar conversion profiles. Conversions of greater than 85% achieved within the first 30 minutes of synthesis. At the lower flow rates, conversion were noted to decrease with decreasing flow rate.

The heighest molecular weight was achieved at the lowest flow rate and decreased with increasing flow rate, with the exception of the 90 mL/min sample. The sample with the highest peak ratio, or purity, of 0.9 was at 90 mL/min and is consistent with the highest PyBS conversion discussed above.

The effect of flow rate on the formation of P(PyBS) was also monitored with synthesis time by GPC. The molecular weight distributions have been grouped into

four classes of less than 1000, 1000-2000, 2000-3000 daltons and the maximum observed (peak) molecular weight. Each class has been experessed as a percentage of the total polymer observed in the GPC anlaysis. At 30 mL/min there was relatively equal amounts of each polymer fraction present. This trend reversed after 60 minutes of synthesis when the lower molecular weight fractions were converted to higher molecular weight species. After 90 minutes of syntesis there was still significant amounts of lower molecular weight fractions, although continuing the syntheis for a longer time could have improved this situation. A similar trend was observed for 60 mL/min, but at 90 mL/min the lower molecular weight components were nearly converted to high polymer.

Interestingly, the molecular weight of the largest fraction at 6200 Daltons did not increase significantly after consumption of the lower molecular weight components. The rapid increase in molecular weight observed for 30 to 90 mL/min sample occurs when the monomer had undergone 80 % or better conversion. At 120 mL/min, the trend obsreved at the lower flow rates is reversed, with the lower molecular weight fractions becoming more significant with increasing synthesis.

The highest conductivity of 0.01 S/cm was observed at 90 mL/min. Electrical conductitiy appeared to be dependent upon molecular weight with the lower coductivities arising from the lower presence of the molecular weight fractions. At 90 mL/min these lower molecular weight components were at a minimum, hence the conductivity was higher. This also implies that conductivity can be significantly improved if the P(PyBS) polymer can be synthsised at higher molecular weights with a mono-disperse molecular weight.

From the above results it was determined that a electrolyte flow rate of 90 mL/min should be preferred as it represents the optimum for maximising monomer conversion, product purity and conductivity. The highest molecular weight was achieved at the lowest flow rate of 30 mL/min. This flow rate resulted in the formation of a significant amount of low molecular weight polymer, had poor monomer conversion and reduced product purity and conductivity.

Example 16: Homopolymer Optimisation: Stage 2 - Variation of Applied Potential The influence of applied potential, from 0.55 to 0.95V in 100 mV increments, on the synthesis of P(PyBS) was invesitgated using the optimum flow rate of 90 mL/min, 0.1 M PyBS and 0.2 M NaNO3. Conversion was noted to increase with increasing potential. Conversion trends were similar for all responses 0.65 V and above, while at 0.55 V the conversion rate was slower end less efficient. Potentials of 0.75 V and above have conversion efficiencies 90 % or better.

The P(PyBS) molecular weight after 90 minutes of synthesis increased with applied potential. Above 0.65 V the peak ratio of the average and peak molecular weight fractions were observed to be above 0.9 indicating that at these higher potentials, the final product had a high level of purity. At 0.55 V the peak ratio was 0.53 indicating that at this potential the electrode processes were less efficient than the higher potentials.

At 0.55 V the polymer was observed to have a high proportion of low molecular weight or oligomer fractions throughout the entire synthesis. This result is consistent with the data discussed above and indicates poor electropolymersiation. At 0.65 V the low molecular weight species produced during the early stages of synthesis were slowly converted into the desired high molecular weight product. Similar trends were observed for 0.75 V, 0.85 V and 0.95 V. The time to achieve conversion of 90% (or better) for the highest molecular weight fraction decreased from 60 minutes at 0.75 V to 15 minutes at 0.95 V indicating improved electro-efficiency at the higher potentials.

The optimum electrical conductivity was found to be 0.01 S/cm when a potential of 0.75 V. At higher potentials than 0.75V the'lowest conductivities out of all of the samples were observed. At potentials lower than 0.75 V, the resultant conductivities were better than the higher potentials but were still significantly lower. The 0.65 V sample had a conductivity of a similar order to the 0.75 V sample, but probably needed a longer synthesis time to convert to a more conductive form. The higher potential samples probably suffered over-oxidation effects. Under these conditions the monomer and low molecular weight oligomers were quickly converted to leave the high polymer that was subsequently damaged by the prolonged exposure to the higher potentials.

Thus, the formation of P(PyBS) can be achieved quickly when a preferred applied potential of 0.65 V to 0.95 V is applied. Molecular weigth also increases with

increasing applied potential with a high degree of monomer conversion. At potentials higher than 0.75V there is evidence of significant polymer over-oxidation. The results presented above suggest that the P(PyBS) is sensitive to applied potential and that prolonged synthesis past the point where the available monomer or low molecular weight oligomer is consumed can be detrimental. In the case of the 0.75 V sample, the synthesis conditions placed this sample at the edge of this effect, hence the electrical conductivity did not suffer the property degradation that were observed. This also implies that conductivity could be further improved if synthesis could be terminated at the point where these degradative processes are initiated. For the above reasons, the 0.75 V sample was preferred as it represents the optimal condition for the following studies.

Example 17: Homopolymer Optimisation: Stage 3 - Variation of PyBS Concentration The effect of varying the PyBS monomer concentration from 0.05 to 0.10 and 0.15 M was made with the optimal conditions of 0.75 V and a flow rate of 90 mL/min, using 0.2 M NaNO3 as the supportng electrolyte. The influence of monomer concentration on conversion after 90 minutes of synthesis is shown in Figure 34. These results clearly illustrate that 0.1 M PyBS performs better under these synthesis conditions.

The highest molecular weigtht was obtained at 0.05 M PyBS and decreased as the PyBS concentration increased. The ratio between the average and peak molecular weights showed that the highest product purity was achieved at 0.05 M PyBS and decreased with increasing monomer concentration. Eventhough this decreasing trend was observed, it must be noted that these ratios were large when compared with the other systems that have been discussed above.

At 0.05 M PyBS there is quick conversion to the highest molecular weight fraction of 8900 daltons with the electropolymerisation complete after approximately 45 to 60 minutes. At 0.1 M PyBS the conversion is slower but has good conversion of the low molecular weight species to high polymer. At 0.15 M PyBS the reaction is clearly incomplete with a large amount of intermediate oligomer species present.

The effect of monomer concentration on electrical conductivity is shown in Figure 37. The optimal conductivity was found to be at 0.2 M PyBS. The conductivity of the sample synthesised at 0.05 M PyBS was noted to be the lowest and was probably due to

overoxidation of the polymer due to the rapid consumption of the monomer within the early stages of synthesis. At 0.15 M PyBS the electrical conductivity was slightly higher than the 0.05 M PyBS condition but was significantly lower due to incomplete conversion of the polymer under the synthesis conditions being used.

The optimal monomer concentration was found to be 0.10 M PyBS as this condition gave the highest electrical conductivity and an intermediate molecular weight of 6200 daltons. Although the lower monomer concentration yields higher molecular weight polymer, this advantage was offset by the overoxidation effects that resulted from the monomer being rapidly consumed in the early stages of synthesis. The highest monomer concentration of 0.15 M exhibited incomplete reaction of the monomer and intermediates. These effects could possibly be avoided if the synthesis time was modified to suit the available monomer to either avoid over-oxidation or incomplete conversion.

Example 18: Homopolymer Optimisation: Stage 4 - Variation of Supporting Electrolyte The effect of changing the electrolyte, from 0.2 M NaNO3 to 0.2 M pTS and no electrolyte, using the optimum 0.75 V, 90 mL/min flow rate and 0.10 M PyBS conditions, on the conversion of PyBS after 90 minutes of synthesis was also examined.

The best conversion for all of the investigated systems was found to be in the absence of supporting electrolyte. The pTS electrolyte was found to give the most inefficient monomer conversion and was noted to be more difficult to synthesise than all other materials (ie. large iR effect within the cell).

The effect of electrolyte on the molecular weight after 90 minutes of synthesis presented a different picture. The pTS sample produced the highest molecular weight of all systems investigated with only synthesis at 0.95 V giving similar values. The lowest molecular weight was found to be in the presence of NaNO3. The ratio between the average and peak molecular weight fractions was also the highest with respect to all other systems previously investigated. The pTS and no electrolyte systems had the best performance of 95 % or better. The high peak ratio values were a result of the polymersiation being carried out under near optimal conditions.

The NaNO3 sample exhibits the early formation of a large amount of intermediate oligomers, followed by the conversion of thes oligomers to the high polymer. In the case of pTS, these intermediate species were less prevalent and the system tended to form mainly the high polymer fraction. Intersetingly, the pTS system did not form any copolymer fraction at 2000 to 3000 Daltons. In the case of no electrolyte, no intermediate species were present after 15 minutes of synthesis with all of the material converted through to the highest molecular weight fraction.

The highest electrical conductivity was observed for the NaNO3 electrolyte (0.01 S/cm) followed closely by pTS (0.0062 S/cm), with no electrolyte (5.0 x 1 10-5 S/cm) approximately three orders of magnitude less conductive than NaNO3. In the case of the NaNO3 electrolyte, the system was close to optimisation and the effects of over- oxidation are minimal. The pTS electrolyte exhibited quick growth, with few intermediate species present in solution prevent the polymer from becoming overoxidised during the 90 minute synthesis. The amount of the high molecular weight fraction was noted to decrease from 75 to 90 minutes giving further evidence for the degradation of the pTS sample at longer synthesis times. In the case of no electrolyte, only the high molecular weight fraction formed during the synthesis. Given the trends observed for the other systems, where the presence for oligomeric intermediates is nescessary for the formation of high conductivity, this sample was open to degradation throughout the entire synthesis and resulted in the lower conductivity.

Under the conditions investigated the NaNO3 electrolyte gave a polymer with the highest electrical conductivity. The pTS polymer, although the most difficult to polymerise, had a considerably higher moleclar weight than the NaNO3 system and a conductivity in the same order as the NaNO3. Given the evidence for the over-oxidation of the polymer in the presence of pTS after 90 minutes of synthesis, shorter synthesis time may result in better conductivities and a higher molecular weight product. In the case of no electrolyte, this system is inherently predisposed to over-oxidation and as a result should only be used with very short synthesis times (ie. < 15 min). This approach is feasible given the high rate of conversion that can be achieved within the cell.

Example 19: Copolymerisation studies - Stationary and RDE Co-polymerisation Given the efficiency of the electropolymerisation of the PyBS - monomer, an investigation into co-polymerisation of PyBS and pyrrole (Py) was made. These studies were made so as to minimise the amount of PyBS monomer in the synthesis electrolyte in order to reduce the final synthesis costs.

Co-polymerisation studies were made by performing a series of rotating disk electrode (RDE) and stationary electrode studies on the co-polymer of Py and PyBS. Co- polymers were investigated at Py / PyBS molar ratios of 50 / 50 (0.05 M / 0.05 M), 25 / 75 (0.025 M / 0.75 M) and 10 / 90 (0.010 M / 0.090 M) to give a total monomer concentration of 0.1 M. CV's and chronoamperograms have been attached as Appendix 2. All experiments were carried out on a 5 mm diameter Pt electrode at a scan rate of 50 mV/s with electrode rotation speeds of 0, 500, 1000 and 1000 rpm for a total of 5 cycles.

All chronoamperometric studies was carried out at 0.75 V (vs. Ag/AgCl). General trends for these studies are discussed below.

Example 20: Characterisation of polymer - CV and Chronoamperogram studies (i) Py/PyBS 50/50 In CV studies at a stationary electrode the copolymer was observed to coat the Pt electrode. No CV peak growth was noted and the deposited film had a passivating character. At 500 and 1000 rpm this CV trend was reversed as there was slight peak growth with the later cycles tending overlay. A thick tough co-polymer coating formed on the electrode surface during all CV experiments and no soluble polymer could be detected in solution. Chronoamperometric studies at 500 and 1000 rpm exhibited and increasing current indicating polymer deposition. The current signal also fluctuated during film growth indicating alternate growth and passivation of the deposited film. A thick adherent film formed at the electrode surface with no evidence of soluble copolymer formation.

(ii) Py/PyBS 25/75 Similar trends were observed in the CV studies on the 25/75 Py/PyBS co- polymer. At a stationary electrode the CV had showed passivating characteristics. At 500 and 1000 rpm this trend reversed with the peak growth increasing and the later cycles overlaying. This CV trend then reversed at 1500 rpm to the passivating trends observed

at 0 rpm. The chronoamperometric growth of the 25/75 copolymer at a stationary electrode exhibited a decreasing electrode current indicative of electrode passivation and consistent this the results observed for the CV study. At 500rpm this trend was reversed, as noted in the CV study, and a stable oxidation current increasing slowly with time was noted. At 1000 rpm a stable current response was noted but small decrease in oxidation time as the synthesis extended. At 1500 rpm the electrode response passivated as observed by the CV study under similar conditions. In both chronoamperometric and CV studies thick film formation was noted with no significant discolouration to the electrolyte to suggest soluble polymer formation.

(iii) Pv/PyBS 10/90 Identical CV trends as observed for the 50/50 and 25/75 Py/PyBS co-polymer studies were noted under 10/90 Py/PyBS conditions. At 0 rpm the CV had passivating characteristics. Upon electrode rotation at 500 and 1500 rpm clear peak growth was observed indicating polymer deposition. At 1500 rpm the CV returned to the passivating character observed at 0 rpm. Chronoamperometric studies at 500 and 1000 rpm initial current growth but at 1000 rpm there was a slight decrease of the observed current, although the deposit at the electrode surface did not passivate. Under both CV and chronoamperometric synthesis conditions a film was formed at the electrode surface but the deposit was not compact but rather crumbly in character. The electrolyte also exhibited some darkening indicative of some water-soluble polymer formation.

Example 21: Co-polymerisation of PoIy(Pyrrole-co- I4-(3-pyrrolyl)] butane sulfonate).

Following the results form the above copolymerisation studies the 10/90 Py/PyBS system was chosen for scale studies in the electrochemical flow cell Poly(Pyrrole-co-(4-(3-pyrrolyl))butane sulfonate), abreviated to P(Py/PyBS) was synthesised electrochemically by flowing the anolyte solution through a electrochemical flowthrough cell. The cell consisted of an anode compartment filled with reticulated vitreous carbon (RVC) with a 60 pore per inch (PPI) porosity (surface area 39.4 cm2/cm3). This anode was sandwiched between two RVC cathodes of similar dimensions and separated by an anion exchange membrane (Neosepta) to prevent mixing between the anode and cathode compartments.

Synthesis was carried out under the following conditions: Anode: 0.0901 M PyBS (aq), 0.00974 M Py and 0.2 M NaNO3 (at)(100 mL by SVF).

Cathode: 0.5 M NaNO3 (aq) (500 mL by SVF) Applied + 0.75 V vs Ag/AgCl for 4 hours.

Flow Rate: 120 mL/min The UV-vis spectrum suggested that the copolymer growth decreased significantly after 2 hours of synthesis with less free polymer in solution at longer synthesis times. After 4 hours of synthesis the soluble fraction of the P(PyBS) was dialysed to remove excess monomer and supporting electrolyte. There was a significant fraction of polymer deposited at the RVC anode surface. It was found that this fraction could be removed by washing the RVC anode in ca. 300 mL water. This fraction was also dialysed.

Example 22. Characterisation of ploymer - GPC Molecular weight analysis was preformed on soluble and deposited (resolubilised) copolymer fractions using GPC the method described above. The GPC report for the soluble and deposited fractions of the P(Py/PyBS) copolymer are summarised below.

Soluble Fraction of P(Py/PyBS) Mn = 4747 <BR> <BR> <BR> <BR> Mew=6521 <BR> <BR> <BR> <BR> <BR> <BR> PDI = 1.374 Deposited Fraction of P(Py/PyBS) My=6643 Mw= 15386 PDI = 3.436 The deposited fraction of the P(Py/PyBS) copolymer had a molecular weigth approximately 2000 Daltons higher than the solution fraction. This result is consistent with the homopolymer molecular weights discussed earlier in this report.

The GPC trace for the copolymer is shown in Figure 24. These results indicate that the majority of the co-polymer was formed within the first hour of synthesis. At later synthesis times there was less polymer present in solution with no change in the

molecular weight determined at each sample time. This implies that polymer was actually lost from the electrolyte solution to the anode surface. As indicated by the results presented for the homopolymer, the formation of the copolymer is a fast process with the reaction complete within the first hour of electrosynthesis. Significantly, there was no improvement in molecular weight by the adoption of a copolymer system. In fact, the molecular weight was lower (ca. 2000 - 3000 Daltons) than the homopolymer of P(PyBS).

HPLC analysis of the P(Py/PyBS) synthesis electrolyte was made using the method discussed above. It was noted that all of the available PyBS monomer was depleted after 60 minutes of synthesis. Secondly, the maximum yield of P(Py/PyBS) copolymer also coincided with the depletion of the PyBS monomer after 60 minutes of synthesis, as confirmed by GPC.

Example 23: Conductivity of P(PyBS) Homopolymer and P(Py/PyBS) copolymer.

The electrical conductivity of the P(PyBS) homopolymer and P(Py/PyBS) 10/90 copolymer was determined using the four probe technique. The test sample was prepared by combining the soluble and deposited fractions and dialysing for 48 hours. The polymer was then reduced to dryness by rotary evaporator and then re-dissolved in ca. 5 mL water. This solution was then cast onto a glass slide with a mask to give a rectangular sample of dimensions ca. 25 x 3 x 0.05 mm. The conductivity of the P(PyBS) homopolymer was determined to be (1.2 + 0.3) x 10-3 S/cm while the P(Py/PyBS) copolymer had a conductivity of (3.5 + 0.7) x 10-3 S/cm.

Although the foregoing describes specific embodiments of the invention, modifications apparent to the skilled addressee fall within the scope of the invention.