TITLE “Thin films with PPO base with crystalline nanoporous phases or active co-crystalline phases with chain orientation perpendicular to the film plane and procedure for the obtainment thereof’

FIELD OF THE INVENTION

The present invention relates to thin films with PPO base with crystalline nanoporous phases or active co-crystalline phases with chain orientation perpendicular to the film plane (c-perpendicular orientation) and a procedure for the attainment thereof. In particular, the PPO film has a thickness lower than 25pm and crystalline nanoporous phases or active co-crystalline phases with a degree of orientation f _c -0.05 and preferably f _c -0.10. More particularly, the procedure comprises the absorption/desorption of host molecules (guest) by an amorphous PPO film in controlled kinetics absorption conditions.

STATE OF THE ART

Crystalline nanoporous phases are characterized by the presence of molecular-size cavities, which can be used for hosting and possibly releasing host molecules with low molecular mass.

Crystalline nanoporous phases are well-known for two commercial polymers, syndiotactic polystyrene and poly(2,6-dimethyl-1 ,4-phenylene)oxide (commonly known as polyphenylene oxide or by means of the acronym PPO).

In the scientific literature article Nagendra, B.; Cozzolino, A.; Daniel, C.; Rizzo, P.; Guerra, G.; Auriemma, F.; De Rosa, C.; D’Alterio, M. C.; Tarallo, O.; Nuzzo, A. “Two Nanoporous Crystalline Forms of Poly(2,6-dimethyl-1 ,4-phenylene)oxide and Related Co-Crystalline Forms”, Macromolecules 2019, 52, 9646-9656 it is described that the PPO comprises two crystalline nanoporous forms, respectively termed form a and form (3, easily recognizable by applying the WAXD (wide-angle X-ray diffraction) and FTIR (Fourier transform infrared) techniques.

Such crystalline nanoporous phases are obtained starting from co-crystalline phases, i.e. from crystalline phases which contain host polymer chains and guest molecules with low molecular mass. The obtainment of crystalline nanoporous phases occurs following the removal of the host molecules from co-crystalline phases, with suitable techniques, such as for example shown in the patent LIS2013280534 or in the scientific literature article Guerra, G.; Daniel, C.; Rizzo, P.; Tarallo, O., “Advanced materials based on polymer cocrystalline forms”, J. Polym. Sci., Part B: Polym. Phys. 2012, 50, 305-322.

PPG specimens with crystalline nanoporous phases are capable of absorbing high amounts of host molecules even when these are only present in traces, as is shown for example in the scientific literature article Daniel, C.; Longo, S.; Fasano, G.; Vitillo, J. G.; Guerra, G., “Nanoporous Crystalline Phases of Poly(2,6-Dimethyl-1 ,4- phenylene)oxide”, Chem. Mater. 2011 , 23, 3195-3200 and in the scientific literature article Daniel, C.; Pellegrino, M.; Venditto, V.; Aurucci, S.; Guerra, G., "Nanoporous- crystalline poly(2,6-dimethyl-1 ,4-phenylene)oxide (PPG) aerogels”, Polymer 2016, 105, 96-103.

Polymers with crystalline nanoporous phases can also have high diffusiveness, i.e. high kinetics of absorption of the host molecules, if produced in the form of specimens with high surface area, such as powders, microfibers and aerogels.

Also known is the possibility to prepare PPG films with crystalline nanoporous phases which have preferred orientations of the chain axes parallel or perpendicular to the film plane, in brief respectively indicated as c-parallel and c-perpendicular orientations, as demonstrated in the scientific literature article Rizzo, P.; Gallo, C.; Vitale, V.; Tarallo, O.; Guerra, G., "Nanoporous-crystalline films of PPG with parallel and perpendicular polymer chain orientations”, Polymer 2019, 167, 193-201.

The known procedures which allow obtaining PPG films with c-perpendicular orientation provide for absorption at room temperature, i.e., 20°C, of several specific host molecules, such as for example dibenzyl ether, carvone and limonene.

SUMMARY OF THE INVENTION

The Applicant has observed that the procedures which are known in the art are only effective for high thicknesses, comprised between 30pm and 400pm, while such procedures lead to the formation of non-oriented films or films with c-parallel orientation, if the thickness of the amorphous starting films is equal to or lower than 25 pm, i.e. for film thicknesses more frequently used by the industrial production world. The method of the present invention intends to overcome the disadvantages of the methods known in the art, and allows obtaining high levels of c-perpendicular orientation also for thicknesses equal to or lower than 25pm.

In particular, the Applicant has observed that with the method of the present invention it is possible to obtain thin films and surface coats (“coating”) with PPO base, having a thickness equal to or lower than 25pm, which contain crystalline nanoporous phases with a c-perpendicular orientation, with a degree of orientation fc — -0.05 and preferably fc^ -0.10.

In addition, the Applicant has observed that the crystalline nanoporous phases obtained with the method of the present invention show a degree of crystallinity above 5% and preferably above 15%.

The Applicant has observed that the formation of the c-perpendicular orientation is affected by the kinetics of absorption of the host molecule in the amorphous PPO.

In particular, the Applicant has observed that the greater the size of the host molecule and the lower the work temperature, both factors which reduce the absorption kinetics, the more one observed the formation of the c-perpendicular orientation.

Starting from such observation, the Applicant undertook a series of tests to evaluate the conditions for the formation of the c-perpendicular orientation as a function of the absorption kinetics. These can be measured by immerging an amorphous PPO specimen in a liquid comprising host molecules and evaluating the increase in weight of the PPO specimen as a function of the immersion time.

After extensive experimentation, the Applicant has surprisingly found that the formation of the c-perpendicular orientation in PPO films having a thickness equal to or lower than 25 pm required the use of host molecules with molecular volume greater than 0.20 nm ³ , preferably greater than 0.25 nm ³ , such as for example carvone, limonene, dibenzyl ether, eugenol and carvacrol, and was facilitated by an absorption kinetics slower than that achievable with the dibenzyl ether at 20°C.

The Applicant has also surprisingly observed that the PPO films having a thickness equal to or lower than 25 pm with c-perpendicular orientation had a transparency to visible light (400-800 nm) clearly greater than that of non-oriented crystalline- nanoporous films or with c-parallel orientation, such characteristic being particularly useful for improving the performance of devices for molecular sensing, above all of optical nature.

Therefore, a first aspect of the present invention is represented by a procedure for preparing a polyphenylene oxide (PPO) film having a thickness equal to or lower than 25 pm with crystalline nanoporous phases with chain orientation perpendicular to the film plane, comprising the following phases:

• preparation of an amorphous PPO film,

• formation of co-crystalline phases by means of absorption of host molecules,

• formation of crystalline nanoporous phases by means of removal of said host molecules, characterized in that said host molecules have a molecular volume greater than 0.20 nm ³ , and said absorption of host molecules occurs with a kinetics slower than that achievable with dibenzyl ether at 20°C.

In a first embodiment of the first aspect of the present invention said host molecules have a molecular volume greater than 0.25 nm ³ .

In a second embodiment of the first aspect of the present invention said host molecules are molecules of organic compounds, preferably selected from the group that comprises or consists of carvone, limonene, dibenzyl ether, eugenol, carvacrol, and mixtures thereof.

In a third embodiment of the first aspect of the present invention, said step of formation of co-crystalline phases takes place at a temperature equal to or lower than 20°C.

In a fourth embodiment of the first aspect of the present invention, said preparation of an amorphous PPO film is carried out by means of melt casting and subsequent cooling or by solution casting and subsequent evaporation of the solvent.

In a fifth embodiment of the first aspect of the present invention, said amorphous PPO film is a self-supporting film or is a coating of a substrate.

In a sixth embodiment of the first aspect of the present invention, said removal of said host molecules takes place by a heat treatment.

In a seventh embodiment of the first aspect of the present invention, said removal of said host molecules takes place by absorption followed by desorption of host molecules of a volatile liquid compound. In an eighth embodiment of the first aspect of the present invention, said removal of said host molecules takes place by supercritical CO2 extraction.

A second aspect of the present invention is represented by a polyphenylene oxide (PPO) film having a thickness equal to or lower than 25 pm with crystalline nanoporous phases with chain orientation perpendicular to the film plane.

In a first embodiment of the second aspect of the present invention, said polyphenylene oxide film has a degree of orientation f _c < -0.05, preferably f _c < -0.10. In a second embodiment of the second aspect of the present invention, said crystalline nanoporous phases have a degree of crystallinity above 5%, preferably above 15%.

In a third embodiment of the second aspect of the present invention, said polyphenylene oxide film is a self-supporting film or a coating of a substrate.

In a fourth embodiment of the second aspect of the present invention, said substrate is made with a material selected from the group that comprises polymers, ceramics, glass, graphite, quartz, silicon and mixtures thereof.

A third aspect of the present invention is represented by a device for molecular separation, nanofiltration or molecular sensing comprising a polyphenylene oxide (PPO) film according to any one embodiment of the second aspect of the present invention.

A fourth aspect of the present invention is represented by a polyphenylene oxide (PPO) film having a thickness equal to or lower than 25 pm according to any one embodiment of the second aspect of the present invention with co-crystalline phases with chain orientation perpendicular to the film plane containing host molecules selected from the group that comprises or consists of molecules of organic compounds with antimicrobial activity, polar compounds and paramagnetic compounds.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows the X-ray diffraction figures, collected by sending the X rays parallel to the PPO film plane, having thickness of about 20 pm obtained in example 1 , which have the crystalline nanoporous phase a. Figure 2 shows the UV-Visible spectra of PPO films having thickness of about 20 pm in crystalline nanoporous form a, obtained in example 1 (curves a, b and c) compared with the spectrum of the amorphous starting PPO film (curve d).

Figure 3 shows the X-ray diffraction figures, collected by sending the X rays parallel to the PPO film plane having thickness of about 20 pm obtained in example 2, which have the crystalline nanoporous phase a.

Figure 4 shows the UV-Visible spectra of PPO films having thickness of about 20 pm in crystalline nanoporous form a, obtained in example 1 (curve (a) and (c)) compared with the spectrum of the amorphous starting PPO film (curve d).

Figure 5 shows the X-ray diffraction figures, collected by sending the X rays parallel to the PPO film plane having thickness of about 20 pm obtained in example 3, which have the crystalline nanoporous phase a.

Figure 6 shows the UV-Visible spectra of PPO films having thickness of about 20 pm in crystalline nanoporous form a, obtained in example 3 (curves (a) and (b)) compared with the spectrum of the amorphous starting PPO film (curve d).

Figure 7 shows X-ray diffraction figures, collected by sending the X rays parallel to the PPO film plane having thickness of about 20 pm obtained in example 4, which have the crystalline nanoporous phase a.

Figure 8 shows X-ray diffraction figures, collected by sending the X rays parallel to the PPO film plane having thickness of about 20 pm obtained in example 5, which have the crystalline nanoporous phase a.

Figure 9 shows the guest induced crystallization kinetics of amorphous PPO films immersed in benzyl ether at room temperature (squares) and in limonene at 40°C (circles) as described in Example 5.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a procedure for preparing a polyphenylene oxide (PPO) film having a thickness equal to or lower than 25 pm with crystalline nanoporous phases with chain orientation perpendicular to the film plane, comprising the following phases:

• preparation of an amorphous PPO film,

• formation of co-crystalline phases by means of absorption of host molecules, • formation of crystalline nanoporous phases by means of removal of said host molecules, characterized in that said host molecules have a molecular volume greater than 0.20 nm ³ , and said absorption of host molecules occurs with a kinetics slower than that achievable with dibenzyl ether at 20°C.

The first step of the procedure of the present invention provides for the preparation of an amorphous PPO film.

The preparation of an amorphous PPO film is carried out by means of melt casting and subsequent cooling or by solution casting and subsequent evaporation of the solvent.

The casting can be attained as coating deposited on a suitable substrate, such as for example a substrate made with a material selected from the group that comprises ceramics, glass, graphite, quartz, silicon, polymers, such as for example ethylene polymers and copolymers, propylene polymers and copolymers, lactic acid polymers, polyamides, and mixtures thereof.

Any procedure of melt casting leads to the formation of an amorphous PPO film, while the obtainment of amorphous PPO films by solution casting requires a suitable selection of the solvent, of the concentration and of the procedure temperature. The solvent is preferably selected from the group that comprises or consists of organic solvents, such as for example chloroform, dichloromethane, tetrachloromethane, dichloroethane, trichloroethane, trichloroethylene, benzene, o-dichlorobenzene, trichlorobenzene, toluene and methyl benzoate. The concentration of the PPO in the solvent are preferably selected in the interval from 1 % to 10%, preferably from 1% to 5% by weight with respect to the weight of the resulting solution. The temperature of evaporation of the solvent is preferably higher than the room temperature, preferably higher than 60°C.

The second step of the procedure of the present invention provides for the formation of co-crystalline phases by means of absorption of host molecules, preferably molecules of an organic compound.

The host molecules have a molecular volume greater than 0.20 nm ³ , preferably greater than 0.25 nm ³ .

The molecular volume of the host molecule can be calculated by means of the following equation: V = M /6 NA where M and S are respectively the molecular mass and the density of the host molecule, and NA is the Avogadro’s number (6.022x10 ²³ ).

The absorption of the host molecules can be carried out via immersion in a liquid or via vapor exposure, preferably via immersion in a liquid. The liquid can be constituted by the pure organic compound or by a solution thereof in inert solvent, i.e. unable to be absorbed.

The absorption kinetics of the host molecules must be slower than the absorption kinetics of dibenzyl ether at 20°C. The absorption kinetics can be evaluated by immerging an amorphous PPO in the organic compound in liquid phase or in a solution thereof and evaluating the increase in weight of the PPO specimen as a function of the immersion time.

The absorption kinetics can be controlled by varying the temperature and/or by using suitable organic compounds or mixtures thereof or solutions in inert solvents, i.e. unable to be absorbed by the PPO, such as for example methanol, acetone or water.

Advantageously, the absorption step takes place at a temperature equal to or lower than 20°C, preferably equal to or lower than 15°C, more preferably equal to or lower than 10°C.

Preferably, the organic compounds used are carvone, limonene, dibenzyl ether, eugenol, carvacrol, mixtures thereof and solutions thereof in inert solvents.

The third step of the procedure of the present invention provides for the transformation of the co-crystalline phases with c-perpendicular orientation into crystalline nanoporous phases with the same orientation, by means of removal of the host molecules.

The removal of the host molecules can be carried out

• by means of a heat treatment,

• by means of absorption followed by desorption of host molecules of a volatile liquid compound, or

• by supercritical CO2 extraction.

Advantageously, the heat treatment occurs at temperatures greater than 30°C, preferably between 30°C and 200°C, more preferably between 50°C and 150°C. The procedure of absorption/desorption of host molecules is preferably conducted at temperatures comprised between 0°C and 80°C, more preferably between 10°C and 50°C.

Preferably, the useful volatile liquid in the present invention is selected from the group that comprises or consists of acetonitrile, acetone, methyl ethyl ketone and methanol.

Advantageously, the procedure of supercritical CO2 extraction is conducted under pressure, preferably at values comprised between 50 and 350 bar, more preferably between 150 and 250 bar, at a temperature equal to or higher than the room temperature, preferably at values comprised between 20°C and 70°C, more preferably between 25° and 60°C, in a time period comprised between 30 and 500 minutes, preferably between 60 and 300 minutes.

The polyphenylene oxide (PPO) film having a thickness equal to or lower than 25 pm with crystalline nanoporous phases with chain orientation perpendicular to the film plane (c-perpendicular) of the present invention can be in the form of self- supporting film or coating of a substrate.

Advantageously, the thickness of the polyphenylene oxide (PPO) film of the present invention is comprised between 1 and 25 pm, in particular between 5 and 20 pm, ends included.

The PPO film of the present invention shows an optical transparency greater than that of non-oriented films with PPO base and much greater than that of films with c- parallel orientation.

In particular, it was determined that for PPO films of the present invention with thickness of about 20 pm, the transmittance in the visible wavelength interval between 400 nm and 800 nm is above 80%, and at the wavelength of 600 nm it is increased by at least 15% and 30% with respect to films with the same crystalline nanoporous phase, but non-oriented or with c-parallel orientation.

The crystalline nanoporous phases comprised in the PPO film can be the form a and/or the form [3 identified and described in the scientific literature article Nagendra, B.; Cozzolino, A.; Daniel, C.; Rizzo, P.; Guerra, G.; Auriemma, F.; De Rosa, C.; D’Alterio, M. C.; Tarallo, O.; Nuzzo, A. “Two Nanoporous Crystalline Forms of Poly(2,6-dimethyl-1 ,4-phenylene)oxide and Related Co-Crystalline Forms”, Macromolecules 2019, 52, 9646-9656. The degree of orientation (f _c ) of the PPO film of the present invention is equal to or lower then -0.05, preferably equal to or lower then -0.10, more preferably equal to or lower than -0.15.

The degree of orientation fc can be measured by means of the method described in the work Rizzo, P.; Gallo, C.; Vitale, V.; Tarallo, O.; Guerra, G., "Nanoporous- crystalline films of PPO with parallel and perpendicular polymer chain orientations”, Polymer 2019, 167, 193-201.

Such method is based on an azimuthal scanning of the reflection with Miller 001 indices, as observed in the diffraction figure of X rays collected with the incident beam of X rays parallel to the film plane (EDGE model).

Such degree of orientation f _c is equal to 0 in the case of crystals that are completely non-oriented, it is equal to -0.5 in the event in which all the crystals in the film have their crystallographic axes c, i.e. the chain axes, perfectly perpendicular to the film plane (c-perpendicular orientation), it is equal to +1 in the event in which all the crystals in the film had their crystallographic axes c, i.e. chain axes, perfectly parallel to the film plane (c-parallel orientation).

The degree of crystallinity of the crystalline nanoporous phases of the PPO film of the present invention is equal to or higher than 5%, preferably above 15%.

The degree of crystallinity for PPO film is measured by means of differential calorimeter (DSC) measurements, evaluating the enthalpy of fusion of the specimen and assuming that the enthalpy ef fusion of the completely crystalline specimen is equal to 43 J/g.

The polyphenylene oxide (PPO) film having a thickness equal to or lower than 25 pm with crystalline nanoporous phases with chain orientation perpendicular to the film plane (c-perpendicular) of the present invention is adapted to be used for different applications, for example in devices for molecular separation, for nanofiltration or for molecular sensing, above all of optical nature, where their greater transparency constitutes a considerable advantage with respect to other materials and with respect to the same PPO with c-parallel orientation or nonoriented.

In addition, the polyphenylene oxide (PPO) film having a thickness equal to or lower than 25 pm with crystalline nanoporous phases with chain orientation perpendicular to the film plane (c-perpendicular) of the present invention is adapted to attain PPO films with co-crystalline phases with chain orientation perpendicular to the film plane containing host molecules selected from the group that comprises or consists of molecules of organic compounds with antimicrobial activity, polar compounds and paramagnetic compounds.

Examples of compounds with antimicrobial activity are represented by ethanol, methyl-p-hydroxybenzoate, thymol, eugenol and carvacrol. PPO films with cocrystalline phases comprising host molecules of compounds with antimicrobial activity have application in packaging microbe-sensitive goods, such as for example medical devices.

Examples of polar compounds are represented by para-nitroaniline. PPO films with co-crystalline phases comprising host molecules of polar compounds have application in films with ferroelectric properties, to be used in sensors or actuators or storage devices.

Examples of paramagnetic compounds are represented by 2,2,5,5-tetramethyl-4- piperidin-1-oxyl (TEMPO). PPO films with co-crystalline phases comprising host molecules of paramagnetic compounds have application in the preparation of molecular materials and devices.

The present invention will now be illustrated with reference to materials and methods described by way of non-limiting example in the following experimental part.

EXPERIMENTAL PART

Example 1

A PPO film (Film (a) of the invention) with thickness of 20 pm with crystalline nanoporous phase a, whose chain axes have a c-perpendicular orientation, with fc = -0.18 the following procedure of the invention was obtained:

• preparation of an amorphous film of 16 pm thickness by means of casting procedure at 60°C from a chloroform solution with a polymer concentration of 2% by weight,

• crystallization in the co-crystalline phase by immerging the amorphous film in dibenzyl ether at 5°C for 6 hours, and

• removal of dibenzyl ether by means of absorption/desorption of acetonitrile at room temperature. X-ray diffraction figure, collected by sending the ray parallel to the film plane (EDGE model), for the film (a) with crystalline nanoporous phase is shown in figure 1 a. Diffraction figure shows that the arcs that correspond to the hkO indices are centered on the meridian and therefore indicate the presence of a c-perpendicular orientation. The diffraction peaks at 20 = 4.5°(100), 7.1 °(010), 9.0°(200), 11.3°(210), 15.1 °(310) clearly indicate the presence of the crystalline nanoporous form a.

The quantitative evaluation of the degree of orientation of the film (a), carried out by an azimuthal scanning of the reflection 001 , has allowed determining fc = -0.18.

The quantitative evaluation of the degree of crystallinity % _c of the film (a), carried out by means of DSC scanning and evaluation of the enthalpy of fusion, has allowed determining % _c = 41 %.

X-ray diffraction figure of EDGE type, for a PPG film (comparison film (b)) with a thickness of 20 pm crystallized by the absorption of dibenzyl ether at 20 °C, i.e. with the procedure already described in the literature, is shown in figure 1 b, after removal of the host molecules. The diffraction peaks of form a, present as rings, clearly indicate the presence of the crystalline nanoporous form a, but the absence of orientation.

The x-ray diffraction figure of EDGE type, for a PPO film (comparison film (c)) with a thickness of 20 pm obtained from a casting procedure at room temperature from 1% trichloroethane (TCE) solution, is shown in figure 1c, after removal of the host molecules. The diffraction peaks of the form a, present as arcs centered on the equator of the figure, indicate the presence of a c-parallel orientation of the crystalline nanoporous form a.

The UV-Visible spectra of the aforesaid films (a), (b) and (c) are compared in figure 2 with that of an amorphous film with the thickness of about 20 pm.

The film (a) of the invention with c-perpendicular orientation has a transparency in the visible region (curve a) not far from that of the amorphous film (curve d). In the entire region of the visible spectrum (400-800 nm), the film (c) with a c-parallel orientation has a clearly lower transparency (curve c) while the non-oriented film (b) has an intermediate transparency (curve b).

In particular, the transmittance at 600 nm of the film (a) with c-perpendicular orientation is 90%, equal to that of the amorphous film (d), while it is reduced to about 70% for the non-oriented film (b) and to about 44% for the film (c) with c- parallel orientation.

Example 2

A PPO film (Film (c) of the invention) with thickness of 20 pm with crystalline nanoporous phase a, whose chain axes have a c-perpendicular orientation, with fc = -0.3, is obtained with the following procedure of the invention:

• preparation of an amorphous film of 16 pm thickness by means of casting procedure at 60°C from a chloroform solution with a polymer concentration of 2% by weight,

• crystallization in the co-crystalline phase by immerging the amorphous film in a 50/50 by weight dibenzyl ether/limonene solution, at 20°C for 2 hours, and

• removal of the host molecules (dibenzyl ether and limonene), by means of absorption/desorption of acetonitrile at room temperature.

X-ray diffraction figure of EDGE type of the film (c) thus prepared in shown in figure 3c. The diffraction peaks clearly indicate the presence of the crystalline nanoporous form a. The arcs which correspond to the indices hkO are centered on the meridian and thus indicate the presence of a c-perpendicular orientation. The quantitative evaluation of the degree of orientation, by azimuthal scanning of the peak 001 , has allowed determining fc = -0.3. The quantitative evaluation of the degree of crystallinity %c of the film (c), carried out by means of DSC scanning and evaluation of enthalpy of fusion, has allowed determining _c = 44%.

The X-ray diffraction figure of EDGE type of the films crystallized via absorption at 20°C of only dibenzyl ether and only limonene are shown for comparison in figures 3a and 3b, respectively. The film (a) crystallized by absorption of dibenzyl ether at 20°C is essentially non-oriented (fc ~ 0, figure 3a) while the film (b) crystallized following absorption of only limonene has a low degree of c-perpendicular orientation (0 > fc > -0.05 ), moreover associated with a lower degree of crystallinity (% _c ~ 30%, from DSC measurements of the enthalpy of fusion).

The UV-Visible spectra of the aforesaid films (c) and (a) are compared in figure 4 with that of an amorphous film with thickness of about 20 pm. The film (c) of the invention with c-perpendicular orientation has a transparency (curve c) only slightly lower than the transparency of the amorphous film (curve d - T=90%). In the entire region of the visible spectrum (400-800 nm), the non-oriented film (a) (curve a) has a clearly lower transparency.

In particular, the transmittance at 600 nm of the film (c) of the invention with c- perpendicular orientation is 87%, substantially similar to 90% of the amorphous film (d), while it is reduced to about 70% for the non-oriented film (a).

Example 3

For the attainment of this example, PPO films were used having thickness of about 20 pm containing the crystalline nanoporous form a

(a) with c-parallel orientation, prepared according to the procedure described in example 1 (by casting procedure at room temperature of a solution of the PPO in TCE, which has X-ray diffraction figure of figure 1c), or

(b) with c-perpendicular orientation, prepared according to the procedure described in the example 2 (absorption of solution dibenzyl ether/limonene at room temperature, which has the X-ray diffraction figure of figure 3c).

The two films are introduced for 1 h in pure eugenol (well-known antimicrobial compound) at room temperature.

Following desorption at room temperature of eugenol by the two films for one day, the eugenol content of the two films becomes close to 15%, typical sum of host molecules in the crystalline nanoporous phase of the PPO.

The diffraction figures of EDGE type of the films (a) and (b) containing co-crystalline phases PPO/eugenol are respectively shown in figures 5a and 5b.

The centering of the reflections hkO on the equator (figure 5a) and on the meridian (figure 5b) clearly indicate that the absorption of large quantities of eugenol has not changed the type of orientation of the two starting films. Quantitative evaluations of the degree of orientation, based on azimuthal scans of the reflection 001 , indicate that it remains essentially unchanged.

The UV-Visible spectra of the films (a) and (b) are compared with that of the amorphous starting specimen (d) in Figure 6.

It is evident that the film (b) of the invention (curve b) has a transparency not far from that of the amorphous film (d) (curve d). In the entire region of the visible spectrum (400-800 nm), the film (a) with c-parallel orientation (curve a) has a clearly lower transparency.

In particular, the transmittance at 600 nm of the film (b) of the invention with c- perpendicular orientation is 85%, slightly lower than the value 90% of the amorphous film (d), while it is reduced to about 41 % for the film (a) with c-parallel orientation.

Example 4

A PPO film (Film (b) of the invention) with 20 j m thickness with crystalline nanoporous phase a, whose chain axes have a c-perpendicular orientation, with fc = -0.3, is obtained with the following procedure of the invention:

• preparation of an amorphous film of 16 pirn thickness by means of casting procedure at 60°C from a chloroform solution with a polymer concentration of 2% by weight,

• crystallization in the co-crystalline phase by immerging the amorphous film at the interface of a water/dibenzyl ether mixture, at 20°C for 30 minutes, and

• removal of the host molecules (water and dibenzyl ether), by supercritical CO2 extraction at 40°C and 250 bar for 1 hour.

The X-ray diffraction figure of EDGE type of the film (b) thus prepared is shown in figure 7b. X-ray diffraction figure of EDGE type of the same film crystallized via absorption at 20°C of only dibenzyl ether is shown for comparison in figure 7a.

Diffraction figure 7b shows that the arcs which correspond to the indices hkO are centered on the meridian and thus indicate the presence of a c-perpendicular orientation. The diffraction peaks at 20 = 4.5°(100), 7.1 °(010), 9.0°(200), 11 ,3°(210), 15.1 °(310) clearly indicate the presence of the crystalline nanoporous form a. The quantitative evaluation of the degree of orientation, by azimuthal scanning of the peak 001 , has allowed determining fc = -0.3. The quantitative evaluation of the degree of crystallinity % _c of the film (c), carried out by means of DSC scanning and evaluation of enthalpy ef fusion, has allowed determining %c - 43%.

Diffraction figure 7a shows only reflection rings, confirming the absence of orientation. Example 5

A nanoporous-crystalline a-form PPO film with a thickness of 20 pm, whose crystalline phase chain axes have a c-perpendicular orientation with fc = -0.27, is obtained by the following three-step procedure:

• preparation of the amorphous PPO film with thickness of about 15pm, by solution casting at 60 ⁰ C, from 2 wt% chloroform solution,

• co-crystallization of the amorphous PPO film by direct immersion in limonene guest at about 40°C, for about 15 min, and

• guest extraction from co-crystalline PPO films by scCO2 extractor at a pressure of 250 bar and at a temperature of 40°C, for 1 hour.

The 2D WAXD EDGE pattern of this film is shown in Figure 8b. For comparison, the 2D WAXD EDGE pattern of the nanoporous-crystalline a-form PPO film, as obtained from the same amorphous film by crystallization induced for immersion in liquid benzyl ether, at room temperature, is shown in Figure 8a

In the 2D WAXD EDGE pattern of Figure 8b, hkO reflections at 20 = 4.5° (100), 7.1° (010), 9.0° (200), 11.3° (210), 15.1 ° (310) appear as arcs centered on the meridian. This indicates the formation of c-perpendicular orientation. A quantitative degree of orientation, as evaluated by using the azimuthal scan of the 001 reflection, allows determining fc = -0.27. The degree of crystallinity of the PPO film is about 45%, as quantified by measuring melting enthalpy of DSC scans. The 2D WAXD EDGE pattern (Figure 8a) of a PPO film, crystallized by benzyl ether guest sorption at 20°C, shows instead only diffraction rings thus indicating the occurrence of unoriented nanoporous-crystalline a-form.

The kinetics of guest induced crystallization of amorphous PPO films, by sorption of benzyl ether guest at room temperature (20°C), and limonene guest at 40°C, are compared in Figure 9.

Figure 9 clearly showed that crystallization kinetic induced by limonene, although conducted at higher temperature, is slower than crystallization kinetic induced by benzyl ether at 20°C.