REVERSE OSMOSIS MEMBRANES

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to and claims priority from commonly owned US

Provisional Patent Applications: 1) US Provisional Patent Application Serial No. 62/453,534, entitled: Chemically Modified Reverse Osmosis Membranes, filed on February 2, 2017; and, 2) US Provisional Patent Application Serial No. 62/490,055, Highly Efficient Reverse Osmosis Membranes, filed on April 26, 2017, both of the disclosures of which are incorporated by reference herein.

TECHNICAL FIELD

The present invention is directed to Reverse Osmosis (RO) membranes. BACKGROUND OF THE INVENTION

Reverse osmosis (RO) is a process that separates components from a fluid stream by passage of the fluid through a porous medium (membrane). In membrane filtration, the membrane acts as a selective barrier that permits passage of some components and water ("permeate" stream) and retains others ("concentrate" stream); splitting one feed- stream into two streams. It is common to classify membranes and membrane separation processes according to the size of the separated components, structure properties, driving force and mode of operation. The major membrane separation processes that are typically used in water systems are: reverse osmosis, nanofiltration (NF), ultrafiltration (UF) and microfiltration (MF). A driving force (active as external pressure) is required to cross the membrane barrier. RO membrane filtration (i.e. desalination) is an active pressure-driven process.

Polyamide thin-film composite (PA-TFC) membranes are currently the main type of membrane used for RO desalination. A thin active polyamide skin is formed on top of a microporous support layer which is usually made of a polysulfone, to create a thin film composite (TFC) membrane. The polyamide layer is formed by interfacial polymerization. The process is based on a polycondensation reaction between two monomers, and occurs at an interface between an aqueous solution containing one monomer (such as meta-phenylenediamine (MPD)) and an organic solution containing a second monomer (trimesoyl chloride (TMC)).

In the desalination process, external pressure, higher than the chemical potential, motivates water passage through the skin, from the high salt concentration (saline solution), to the low salt concentration area on the support side (desalted water), against the concentration gradient.

Reducing the concentration gradient by altering the difference in free energy between the two sides of the membrane (e.g., virtually increasing the concentration of the desalted water) results in a lower external pressure being required for the process, making the desalination processes more energy efficient. To date, this has been accomplished with the addition of solutes to the desalted water, known as forward osmosis. However, this solute addition requires constant maintenance, rendering solute addition as cost prohibitive.

In typical commercial use, RO membranes are in a spiral wound configuration, where several flat sheet membranes are glued together pair-wise, on three sides to form pockets, with a permeate spacer in between. The membrane pockets are rolled around a tube creating feed and permeate channels. The spiral wound units are enclosed in series in a multiple-unit pressure vessel, wherein the number of membrane units per pressure vessels are typically 1 to 8. Example spiral wound RO membrane systems include Model Numbers S-85, S-255, S-850, S-1600, S-3600, S-7200, S-18000 and S-36000, commercially available from New Logic Research, 1295 67 ^th Street, Emeryville, CA 94608, www.vsep.com. FIG. 1 shows a system with multiple pressure vessels 10, each pressure vessel 10 including the aforementioned spiral wound units.

Salt concentration to the membrane feed along a pressure vessel 10 is increased as the permeate water flows to the permeate channels and from one membrane to the next. The concentrate stream after the first membrane element is the feed to the second and soon, thus a feed concentration gradient is created along the pressure vessel 10, as well as an osmotic pressure gradient. As a result, the osmotic resistance to water flow, in the later elements, is higher. At a constant applied pressure this results in lower driving force, thus the water flow through these elements decreases. SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to molecules, membranes, apparatus and systems for RO processes, where the performance improved, e.g. flux is increased without decreasing the salt rejection.

Embodiments of the present invention disclose reverse osmosis (RO) membranes with an additive molecule, for example, a peptoid, covalently bound to one or more molecules of the membrane layers, improving the performance of the membranes when compared to conventional equal non-additive bound membranes (baseline). The disclosed (RO) membranes exhibit greater flux efficiency along each of the units in a multiple unit RO pressure vessel, when compared to the aforementioned baseline unit, e.g., a non-peptoid bound membrane, such as polyamide (PA) thin film composite RO membranes in a spiral wound configuration, where the membrane sheets are formed by interfacial polymerization of meta-phenylenediamine (MPD) and trimesoyl chloride (TMC) (over a support).

Embodiments of the present invention disclose membrane additives and/or modified membranes that require lower pressure to provide a given flux, or provide a greater flux at a given pressure.

Embodiments of the invention are such that the impact said for example percentage of the flux improvement of the chemical modification of the peptoid bound membranes differs in the various RO units of the multiple -unit RO pressure vessel, according to the technological needs.

Embodiments of the invention provide a chemically modified, peptoid additive bound reverse osmosis (RO) membrane exhibiting better performance along the vessel and in each of the units in a multiple-unit RO pressure vessel, when compared to a baseline non-peptoid bound membrane, e.g., a RO spiral wound unit, where the membranes are formed by interfacial polymerization of MPD and TMC (over a support).

According to another aspect, there is provided a method of producing a reverse osmosis membrane, the method comprising:

providing a porous support layer;

providing a skin layer; binding at least one additive molecule, for example, a peptoid molecule to the molecules forming the skin layer (e.g., via meta-phenylenediamine-Peptoid (MPD-P)) and attaching the skin layer to the support layer.

The resultant membrane improves reverse osmosis performance parameters are selected from the group consisting of reduced energy consumption, lower pressure required, higher throughput, higher water recover, improved permeability at various pressures at varied ambient conditions and combinations thereof, when compared to a non-peptoid bound membrane.

Embodiments of the invention are directed to a peptoid of Formula I meta- phenylenediamine-Peptoid (MPD-P):

I

wherein

Ri is NH ₂ , COOH, CH ₃ , or CH=CH ₂

R ₂ is CH ₃ , (CH ₂ ) ₂ OH, or (CH ₂ ) ₂ OCH ₃

R ₃ is C=0, or CONH-CH ₂ -CO and

N is greater than 2.

Optionally, the n is 3 to 7.

Embodiments of the invention are directed to a reverse osmosis (RO) membrane comprising: a support; and, a skin layer comprising a composition of meta- phenylenediamine (MPD) molecules and at least one peptoid additive molecule bound to the MPD molecules (MPD-P).

Optionally, the RO membrane is such that the bond between the at least one peptoid additive and the MPD molecules of the skin layer is includes a covalent bond.

Optionally, the reverse osmosis membrane is such that the at least one peptoid additive molecule is selected from the group consisting of: meta-phenylenediamine- Peptoid (MPD-P) and para-phenylenediamine-Peptoid (PPD-P). Optionally, the reverse osmosis membrane includes an interface between the support and the skin, such that the MPD-P and PPD-P molecules embed at least proximate to the interface.

Optionally, the reverse osmosis membrane is such that the support intermeshes with the skin layer in a physical engagement.

Optionally, the reverse osmosis membrane is such that the support is porous.

Optionally, the reverse osmosis membrane is such that the support is selected from the group consisting of: polysulfones and polyethersulfones (PES).

Optionally, the reverse osmosis membrane is such that the skin layer additionally includes trimesoyl chloride (TMC).

Optionally, the reverse osmosis membrane additionally comprises one or more of molecules including: polyamides, cellulose acetates, polyimides, polybenzimidazole and mixtures thereof.

Optionally, the reverse osmosis membrane is such that the skin layer includes a first layer of a composition of the meta-phenylenediamine (MPD) molecules and at least one MPD-P (meta-phenylenediamine peptoid), and second layer of MPD molecules over the first layer, wherein the MPD-P molecules is not embed in the surface of the membrane body.

Embodiments of the invention are directed to a spiral wound membrane unit for reverse osmosis (RO). The spiral wound membrane unit comprises: a plurality of reverse osmosis membranes, with at least one of the reverse osmosis membranes, comprising: a support; and, a skin layer comprising a composition of meta- phenylenediamine (MPD) molecules and at least one peptoid additive molecule bound to the MPD molecules of the skin layer.

Optionally, in the spiral wound membrane unit, the at least one of the reverse osmosis membranes is such that the bond between the at least one peptoid additive and the MPD molecules of the skin layer is includes a covalent bond.

Optionally, in the spiral wound membrane unit, the at least one of the reverse osmosis membranes is such that the at least one peptoid additive molecule is selected from at least one of: meta-phenylenediamine-Peptoid (MPD-P) and para- phenylenediamine-Peptoid (PPD-P). Optionally, in the spiral wound membrane unit, the at least one of the reverse osmosis membranes includes MPD-P or PPD-P molecules embed at least proximate to the interface between the support and the skin.

Optionally, in the spiral wound membrane unit, the at least one of the reverse osmosis membranes is such that the support intermeshes with the skin layer in a physical engagement.

Optionally, in the spiral wound membrane unit, the at least one of the reverse osmosis membranes is such that the support is porous.

Optionally, in the spiral wound membrane unit, the at least one of the reverse osmosis membranes is such that the support is selected from the group consisting of: polysulfones and polyethersulfones (PES).

Optionally, in the spiral wound membrane unit, at least one of the reverse osmosis membranes is such that the skin layer additionally includes trimesoyl chloride (TMC).

Optionally, in the spiral wound membrane unit, the at least one reverse osmosis membrane additionally comprises one or more of molecules including: polyamides, cellulose acetates, polyimides, polybenzimidazole and mixtures thereof.

Optionally, in the spiral wound membrane unit, the at least one reverse osmosis membrane is such that the skin layer includes a first layer of a composition of the meta- phenylenediamine (MPD) molecules and at least one MPD-P (meta-phenylenediamine peptoid) bound to the MPD molecules, and second layer of MPD molecules over the first layer.

Optionally, in the spiral wound membrane unit, the at least one reverse osmosis membrane includes a plurality of reverse osmosis membranes.

Embodiments of the present invention include a pressure vessel for reverse osmosis including at least one spiral wound membrane unit comprising: a plurality of reverse osmosis membranes, with at least one of the reverse osmosis membranes, comprising: a support; and, a skin layer comprising a composition of meta- phenylenediamine (MPD) molecules and at least one peptoid additive molecule bound to the MPD molecules of the skin layer. Optionally, in the spiral wound membrane unit of the pressure vessel, the at least one of the reverse osmosis membranes is such that the bond between the at least one peptoid additive and the MPD molecules of the skin layer is includes a covalent bond.

Optionally, in the spiral wound membrane unit of the pressure vessel, the at least one of the reverse osmosis membranes is such that the at least one peptoid additive molecule is selected from at least one of: meta-phenylenediamine-Peptoid (MPD-P) and para-phenylenediamine-Peptoid (PPD-P).

Optionally, the pressure vessel includes 1 to 10 spiral wound membrane units.

Embodiments of the invention are directed to a method of synthesis of a meta- phenylenediamine-Peptoid (MPD-P) peptoid of Formula I above, using a solid phase synthesis (SPPS) on a Rink Amide resin. The method comprises the stages of:

i. Resin Fmoc deprotection

ii. Bromoacylation with bromoacetic acid and Ν,Ν'- diisopropylcarbodiimide(DIC)

iii. Amine displacement with methoxyethanamine activated by hydroxybenzotriazole (HOBT) and DIC.

iv. Repetition of stages ii and iii for n-1 times.

v. Amine displacement with glycine activated by HOBT and DIC vi. Coupling boc-l,3-diaminobenzoic acid

vii. Cleavage of the peptoid product from the resin with trifluoroacetic acid; and,

viii. Purification of the peptoid.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the arts to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of a conflict, the specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only, and not intended to be limiting. Throughout this document, all molecules, compositions and references to positions in molecules and/or compositions are in accordance with International Union of Pure and Applied Chemistry (IUPAC) standards. BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

Attention is now directed to the drawings, where like reference numerals or characters indicate corresponding or like components. In the drawings:

FIG. 1 is a photograph of a series of pressure vessels in a desalination unit;

FIG. 2 is a diagram of a membrane manufacturing cycle in accordance with an embodiment of the invention;

FIG. 3A is a diagram of the interfacial polymerization process demonstrating the molecular bonding of a peptoid to other molecules forming the skin of a membrane body in accordance with an embodiment of the invention;

FIG. 3B is an illustration of the MPD-P molecule;

FIG. 3C is an illustration of the covalent bonding of the MPD-P and TMC of the membrane skin;

FIG. 3D is a macroscopic illustration of the membrane body with peptoid tails embedded into the membrane body;

FIGs. 4A and 4B are diagrams of two layers MPD-P embedded membranes;

FIG. 5 is a diagram of a pressure vessel in accordance with an embodiment of the invention and a graph of various parameters associated with potential operation of the pressure vessel;

FIG. 6 is a graph of permeate flux versus applied pressure for a chemically bound peptoid membrane and a membrane absent peptoids in accordance with EXAMPLE 3;

FIG. 7 A is a diagram of a pressure vessel in accordance with EXAMPLE 4; and, FIG. 7B is a graph of permeate flux versus feed salt concentration (Cs), for the peptoid bond membranes and non-peptoid bound membranes in accordance with EXAMPLE 4. DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description. The invention is capable of other binding embodiments, or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

Embodiments of the present invention are directed to compositions of peptoid molecules that are incorporated into RO membranes, such that the RO membranes require lower pressure to provide a given flux, or provide a greater flux at a given pressure. Peptoid molecules are, for example, synthesized on Rink amide resin using a process similar to the standard "submonomer" protocol or Solid State Peptide Synthesis (SPPS). Specifically, the carboxylate of N ^a -Fluorenylmethyloxycarbonyl (Fmoc)-protected (and sidechain-protected) peptoid is activated and then coupled to the secondary amino group of the resin-bound peptoid chain. Removal (deprotection) of the Fmoc group is then followed by addition of the next monomer, as disclosed in Zuckermann, et al., Efficient Method for the Preparation of Peptoids [Oligo(N -substituted glycines)] by Submonomer solid phase synthesis, J. Am. Chem. Soc, 114 (26), pp. 10646-10647 (1992). In other methods, each N-substituted glycine monomer is assembled from two readily available "submonomers" in the course of extending the peptoid olygomer. The submonomer method has been also adapted to a robotic synthesizer, as disclosed in Zuckermann et al., Efficient Method for the Preparation of Peptoids [Oligo(N -substituted glycines)] by Submonomer Solid-Phase Synthesis, Int. J. Pepl. Protein Res. 40, pp. 498-507 (1992).

In this method, peptoids are synthesized with precise control over the sequence of highly diverse side chain functional groups, enabling a robust investigation of structure- property relationships. Peptoids are also synthesized using a "wet" method, for example, of 10-steps synthesis, including: Preparation of trifluoroacetamido ethanol, condensation to 2-trityltrifluoroacetamidoethanol, reduction to 2-tritylamino ethanol, followed by two cycles of bromoacylation and amine displacement steps, condensation of the I ^s and 2 ⁿ cycle products, followed by bromoacylation and amine displacement step, condensation with succinic anhydride, and removing trityl protecting group with acetic acid.

Embodiments of the invention provide peptoids and a peptoid containing molecules, including meta-phenylenediamine peptoid (MPD-P), and para- phenylenediamine peptoid (PPD-P), which are used for the preparation of chemically modified peptoid-bound reverse osmosis (PB-RO) membranes. The MPD-P and PPD-P peptoids are covalently bound to one or more of sheet-membrane rolled in a spiral wound unit, thus imparting the membrane an improved performance as compared to a non- peptoid bound (baseline) membrane (detailed above).

FIG. 2 shows an example process for membrane vessel element manufacturing. Initially, a peptoid tail is covalently bonded to one of the molecules forming the membrane skin, for example MPD - monomer of the membrane; thus, synthesizing for example the MPD-P molecule in which the peptoid is covalently bond to the MPD, in box 202. The membrane sheet is then fabricated, at box 204, by embedding the peptoid additive molecule, for example, MPD-P, into the membrane sheet, known as a skin, by processes including interfacial polymerization. The skin is physically intermeshed with a support, e.g., a porous support, such as polysulfones or polyethersulfones (PES) to complete the membrane, also known as a membrane body (the terms "membrane" and "membrane body" used interchangeably herein). The now fabricated membrane sheets are rolled into a spiral wound unit, at box 206, with the spiral wound units placed into pressure vessels and RO array, which are used in desalination plants, at box 208.

Formation of the RO Membrane

Thin-film composite (TFC) membranes with a polyamide (PA) top selective skin over polysulfone support are the most common reverse osmosis (RO) membranes currently used for desalination and thus these membranes were selected as a starting point for membrane modification.

The thin film composite (TFC) reverse-osmosis membrane is comprised of a porous support layer and a skin layer. The selective skin layer material is typically selected from a group consisting of: polyamides, cellulose acetates, polyimides, polybenzimidazoles and mixtures thereof; the support layer is typically selected from a group consisting of polysulfones, polyethersulfones (PES) and the like.

In a polyamide thin-film composite membrane (PA-TFC), the polyamide layer that plays the role of the secretive membrane skin, is usually a skin of, for example, approximately 100-200 nanometer (nm) thickness, which is formed on top of an approximatelyl50 micrometer (μπι) thick microporous support layer made of for example polysulfone on top of polyester, by an interfacial polymerization (IP) process.

The interface polymerization (IP) membrane-forming process is based on polymerization reaction which occurs at the interface between an aqueous solution containing one monomer and an organic solution containing a second monomer. An amine monomer like meta-phenylenediamine (MPD), or para-phenylenediamine (PPD), both molecular formulae as shown immediately below, and are commonly used to create the aqueous solution in the interfacial polymerization process forming the polyamide skin layer in a thin-film composite membrane. The amine monomer used to form a PA-TFC membrane can be selected from a group consisting of: meta, para or ortho-phenylenediamine.

p-phefiyierte iairisfse (PPD) m-pbenyienediafwfse (MPD)

N-substituted glycine peptoids stand out as an important family of peptidomimetic oligomers. Specific peptoid members of this family, possessing carboxylic end groups and hydroxyl or ether bearing side chains, were found to reduce the freezing point of water more than expected from their individual colligative effects.

It was found that the reduction of freezing point phenomenon may indicate the unexpected interaction effect between these molecules and water molecules, which results in a significant reduction of the water enthalpy. Synthesizing the Peptoid Additive (Molecule) for the RO Membrane

Meta-phenylenediamine peptoid (MPD-P) is a molecule in which the peptoid' s tail is covalently bound to the meta-phenylenediamine (MPD), an aromatic monomer used in the formation of a polyamide RO membrane.

Peptoid molecules are, for example, synthesized on Rink amide resin using a protocol following the standard "submonomer" protocol of the Solid-State Peptide Synthesis (SPPS).

An amine monomer like MPD, of the formula Molecular formula: C24H39N-7O8 bearing a peptoid substituent (MPD-P) at position 5 as shown immediately below is prepared, for example, using a process similar to SPPS or by any other suitable synthetic process. The peptoid substitution can be carried out on other positions and other monomers like PPD forming PPD-P or other similar molecules.

The MPD-P peptoid at position 5 of Molecular formula: C24H39N7O8 is synthesized using a solid phase synthesis (SPPS) on a Rink Amide resin comprising stages i. through vi., as follows:

Stage i. Resin Preparing. Swelling the Rink Amide resin with dichloromethane (DCM) followed by washing with dimethylformamide (DMF). Solvent evacuation is done using a vacuum pump with large trap.

Stage ii. Removing the resin Fmoc protecting group using piperidine in DMF, followed by washing with DMF and DCM.

Stage iii. Synthesis of the peptoid chain. Bromoacylation with bromoacetic acid and Ν,Ν'-diisopropylcarbodiimide (DIC) added to the resin followed by aggregation process, and washing with DMF and DCM. After washing, methoxyethanamine (MEA) is added to the resin.

Stage versus Repetition is performed for n-1 times, where n is the number of repeating monomer units. For example, with the MPD-P molecule shown above, with the molecular formula: C24H39N7O8 there are three repeat units, such that n=3.

Stage iv. Glycine is activated by hydroxybenzotriazole (HOBt) and DIC followed by coupling and washing with DMF, DCM and menthol respectively. A vacuum drying is conducted after the washing step.

Stage v. Cleavage of the peptoid product from the resin with trifluoroacetic acid (TFA) in water and TIS (under a stream of Nitrogen gas).

Stage vi. Precipitation of the concentrated product by addition of ice-cold t- butylmethyl ether (TBME) to the TFA solution followed by centrifugation for separating the product. Washing the separated product in ether, then dissolving it in double distilled water (DDW) and trifluoroacetic acid (TFA), and lyophilized to powder.Characterization of the final product and its purity using RP-HPLC and ESI-MS. The purity should be, for example, approximately at least 90 percent.

The resultant peptoid of Formula I, a metaphenylenediamine peptoid (MPD-P) is synthesized, with the following molecular structure:

Formula I

wherein,

Ri is NH ₂ , COOH, CH ₃ , or CH=CH ₂

R ₂ is CH ₃ , (CH ₂ ) ₂ OH, or (CH ₂ ) ₂ OCH ₃

R ₃ is C=0, or CONH-CH ₂ -CO and

n>2, for example 3-7

Bonding the Peptoid Molecules to the RO Membrane

The peptoid tail is initially covalently bonded to one of the molecules forming the membrane skin layer, for example MPD. By using the synthesis process described above, there results in MPD-P molecule. A membrane peptoid bond sheet is then fabricated, for example, by interfacial polymerization process. A peptoid substituted monomer, for example MPD-P, can be used in the interfacial polymerization membrane forming process replacing some of the MPD monomer; and forming a membrane in which a peptoid molecule is covalently bound to the membrane body. Similar molecules such as PPD-P can be also used in the same process or other, for the same purpose, binding peptoid molecules to the membrane body.

By binding MPD-P molecules to other molecules forming the skin (e.g. TMC) of the membrane body, the resultant skin develops a different structure including a change in the thickness of the polyamide barrier layer and its porosity properties, thus its resistance to water passage. The skin material is chemically similar to a non-additive, no difference in selectivity (intrinsic salt rejection) is expected. The presents of the peptoid in the membrane skin alters the solute local condition and believe to reduce the local free enthalpy of the permeate water; and thus, alters the concentration resistance over the membrane and the thus, lowered the external pressure that is required for the process, making the reverse osmosis desalination processes more energy favorable.

A thin-film composite reverse-osmosis membrane is comprised of a porous support layer, and a selective skin layer, the skin layer formed with at least one peptoid molecule or a peptoid substituted monomer molecule covalently bound to the skin layer, with the peptoid molecules, e.g., at least the tails thereof, targeting the interfacial area in between the skin layer and the support layer. The skin layer and support layer, are typically physically intermeshed with each other.

The skin layer is typically selected from a group consisting of: polyamides, cellulose acetates, polyimides, polybenzimidazole and mixtures; the support layer is typically selected from a group including, for example, poly-sulfone and polyethersulfone (PES).

In one embodiment, the skin layer is a polyamide film layer of MPD-P molecules chemically, e.g., covalently, bound to molecules forming the skin layer. The covalent bonding is achieved, for example, by the addition of a trimesoyl chloride (TMC) organic solution to an aqueous MPD/MPD-P solution.

Membrane skin fabrication (on top of the support layer) is based on a process where an interfacial polymerization process of two aromatic monomers MPD (meta- phenylenediamine) in an aqueous solution and TMC (trimesoyl chloride) in an organic solution, are implemented. As shown in FIG. 3A, membrane skin fabrication on top of a support layer 300 is based on a process of interfacial polymerization (IP Reaction) of two aromatic monomers, MPD (meta-phenylenediamine) and TMC (trimesoyl chloride). MPD-P (meta-phenylenediamine peptoid), shown in FIG. 3B, is used in the interfacial polymerization membrane forming process replacing some of the MPD monomer, for example, in an aqueous solution of 10% MPD-P of total MPD monomer, and forming a membrane where a peptoid molecule is covalently bound to the skin 304 of the membrane body, as shown in FIG. 3C. As shown in FIG. 3D, the resultant membrane 302 includes a skin 304 over the support layer 300, the skin 304 resulting from the interfacial polymerization, with the peptoid tails 306 target the skin 304/support layer 300 interface.

Attention is now directed to FIGs. 4A and 4B. FIGs. 4A and 4B are schematic figures illustrating two layers fabrication processes. This fabrication is based on a common process where an interfacial polymerization process of two aromatic monomers MPD and TMC are implemented.

FIG. 4A is a schematic figure illustrating a two-layer fabrication process. Two single polyamide layers 402, 404, forming the membrane skin, were formed over a support 300. The first layer 402 is formed with MPD-P only, for example, on top of the support layer 300 using a diluted aqueous solution (1:9) containing only the MPD-P. The second layer 404, formed over the first layer 402.

FIG. 4B is another schematic figure illustrating a two-layer fabrication process. Two single polyamide (PA) layers 412, 414, forming a membrane skin, were formed over a support layer 300. The first layer 412 was formed on top of the support layer 300 using a diluted aqueous solution (for example, dilution ratio of 1:9) containing a mixture of MPD-P and MPD at a ratio of 100: 1. The MPD-P to MPD weight ratio was kept constant, for example at 2.5%. Two PA layers were formed. The second layer 414 was composed of MPD.

The example membranes of FIGs. 4A and 4B show that the MPD-P embeds in the interface between the membrane skin 402/404, 412/414 and the respective support (support layer) 300. The membrane skin 402/404, 412/414 is fabricated on top of the support layer 300, with the membrane skin 304 and support layer 300 physically intermeshed to form the membrane body or membrane.

Operation Performance Test of the RO Membranes

The membranes produced by the processes detailed above are operable in spiral wound units in a pressure vessels array, such as those shown in FIG. 1. Turning also to FIG. 5, there is shown an example model pressure vessel 500 with two conventional spiral wound RO (membrane) units 502, 503 and a spiral wound RO (membrane) unit 504 made of the peptoid bound membranes as disclosed above.

The pressure vessel 500 operates as saltwater, e.g., sea water, enters the pressure vessel 500 through a feed inlet 510 and is treated by the successive spiral wound units 502, 503 and 504. Permeate, the desalted water, exits through an outlet 512, while concentrate, the remaining concentrated saltwater, exits through an outlet 514, where, for example, it is returned to the sea.

A theoretical operation of the model pressure vessel 500 is shown graphically over time. As the salt water passes through each of the spiral wound (membrane) units 502, 503 and 504, the driving pressure, i.e., energy needed to force the salt water through the spiral wound units 502, 503, 504, and represented by the line 521, increases for each successive unit. This increase in line 521 is, for demonstrative example, linear. The water flux, measured in product (desalinated) water volume passed through an area of the membrane, for a time period, is for example, represented as:

Flux = Volume of Product Water per square meter (area) of membrane per TIME The flux is illustrated graphically by the line 522. With the pressure vessel 500, flux decreases over time when the salt water is processed into resultant product water by the conventional spiral wound units 502, 503, but levels off while the salt water is passed through and processed by the spiral wound unit 504 made of the peptoid bound membranes as disclosed above. The feed concentration, which is a measure of NaCl in the water, and represented by line 523, increases as the feed water is filtered through consecutive spiral wound membrane units 502, 503, 504. The pressure vessel 500 typically includes one to ten, and for example one to eight spiral wound units, and, for example, five spiral wound membrane units. In accordance with the present invention one or more of these spiral wound units, are for example, spiral wound units of the disclosed peptoid bound membranes. The spiral wound units with the disclosed peptoid bound membranes can be in any order within the pressure vessel.

The flux improvement is determined by comparing the flux in a RO laboratory system mimicking the feed concentration increase in a pressure vessel with membrane provided with the chemically modified peptoid bound membranes of this invention to a similar RO membrane without chemical modification.

EXAMPLES

The following examples are not meant to limit the scope of the claims in any way. The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the described invention, and are not intended to limit the scope of the invention, nor are they intended to represent that the experiments below are all or the only experiments performed. Unless indicated otherwise, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Centigrade, and pressure is at or near atmospheric.

EXAMPLE 1 - Synthesis and purification of the peptoid oligomer MPD-P having the structure of FORMULA II

FORMULA II Molecular formula: C24H39N7O8

Chemical name: di-glycinamide methyl ketone, N'- amide, tri-N",N"',N"'- methylethylether, N'""- 1 ,3-phenylenediamine,5-oxopropyl

Solid-phase synthesis of peptoid oligomers was performed in fritted syringes on Rink amide resin. For example, 2.7 g of resin with a loading level of 0.7 mmol-g-l was swollen in dichloromethane (DCM) for 25 minutes (min), followed by washing the resin three times with dimethylformamide (DMF) for 1 min. Following swelling, the Fmoc protecting group was removed by treatment with 20% piperidine in DMF for 5 min followed by another wash for 20 min and followed by further washing as previously mentioned.

After de -protection and after each subsequent synthetic step, the resin was washed three times with DMF, one minute per wash, and three times with DCM, one minute per wash. Peptoid synthesis was carried out using three cycles of alternating the bromoacylation and amine displacement steps. For each bromoacylation step, a solution of bromoacetic acid (20 eq; 2.8 g) and Ν,Ν'-diisopropylcarbodiimide (DIC, 24 eq; 3.74 mL, added dropwise on water bath) was added to the resin, and the mixture was agitated for 20 min. For better yield, this step was repeated on each cycle (double coupling). After washing, methoxyethanamine (20 equivalents (eq); 1.74 mL) was added to the resin and agitated for 20 min. After the three cycles, glycine (5 eq) was activated by hydroxybenzotriazole (HOBt, 5 eq) and DIC (5 eq) for 10 minutes, before introducing it to the resin for 60 minutes coupling, for maximum yield, this step was repeated prior to Fmoc removal. The Fmoc-removal was achieved as mentioned in this EXAMPLE above, before, the last coupling step used the same procedure (as in this EXAMPLE above) as the glycine coupling, but instead used boc -protected 1,3-diaminobenzoic acid (5 eq). Final washing included using DMF, DCM and methanol respectively. When the desired sequence was achieved, the peptoid products were cleaved from the resin by treatment with 95% trifluoroacetic acid (TFA) in water (2.5%) and TIS (2.5%) for 120 minutes. After filtration, the cleavage mixture was concentrated under a stream of nitrogen gas for volumes less than 1 milliliter (mL). The produced was precipitated by addition of ice- cold t-butylmethyl ether (TBME) to the TFA solution and separated by centrifugation. The solid product was washed once in ether and then dissolved in 24 mL double distilled water (DDW) plus 0.1% Triethylamine (TFA) with 1 mL of acetonitrile lyophilized to powder. Peptoid purity was assessed by reversed phase high pressure liquid chromatography (RP-HPLC) using a C18 130A column. Detection was done by UV absorbance at 220 nm during a linear gradient conducted from 0% to 70% solvent B (25% water in acetonitrile and 0.085%) over solvent A (0.1% TFA in HPLC grade water) in 30 minutes with a flow rate of 1 mL min-1. MS (ESI): m/z = 576.3 calculated for C24H39N708Na [M]+; found: 576.2

EXAMPLE 2 - Preparation of a chemically modified peptoid-bound thin film composite polyamide membrane using the interfacial polymerization process

The membrane-forming system includes meta-phenylenediamine (MPD) in water, and trimesoyl chloride (TMC) in hexane. The PA skin films formed by interfacial polymerization (IP) are supported on microporous polysulfone (PSf) layer.

A polysulfone (PSf) support membrane was immersed in deionized water overnight then removed from the water and positioned on a glass plate. A rubber gasket and a plastic frame were placed on top of the support membrane, and binder clips were used to hold the plate-membrane-gasket-frame stack together. 25 mL MPD solution of 0.015-0.15% MPD-P mixed with 1.5-2% MPD were poured into the frame and allowed to contact the PSf membrane for 2-5 minutes before draining the excess MPD solution. The frame and gasket were disassembled, and residual solution between the plate and the PSf membrane was removed using paper towels. Residual droplets of solution on the top surface of the PSf membrane were removed by rolling a rubber roller across the membrane back one time. Afterwards, the frame and gasket were dried and reassembled on top of the PSf membrane, and 15 mL of 0.5-0.1% (w/v) TMC/hexane solution were poured into the frame. After a few seconds, the TMC/ hexane solution was drained from the frame, and the frame and gasket were disassembled. The membrane was dried in air at ambient conditions for 10 min. Finally, the entire membrane was immersed in deionized water, and kept at 4°C until use. Example 3-Comparison between Peptoid Bund Membranes and Baseline Membranes

The MPD-P embedded membranes produced and described above, performed in terms of flux as a function of applied pressure. Flux was measured on a range of pressures between 48-58 bar. Experiments were conducted in a cross-flow cell at 25°C, with 32 gr/L NaCl feed solution, using flat-sheet membrane samples of 63 cm .

FIG. 6 presents flux versus applied pressure for peptide bound membranes (line 600) disclosed above, compare to baseline, i.e., non-peptoid bound membranes (line 602), these baseline and non-peptoid membranes as described in the BACKGROUND Section above, which are membranes produced above before peptoids are covalently bonded to the molecules of the membranes.

Line 600 shows improved performance of the peptoid bound membrane. As shown, the line 600 has shifted the flux/pressure relationship to the upper left. This means that the peptoid bound membrane achieves the same flux as the baseline membrane (line 602), at a lower pressure.

A flux of 20 LMH (liters/square meter/hour) at 5 bars less than that of the baseline membrane was achieved. An even greater improvement for a flux of 30 LMH was achieved for the peptoid bound membrane exhibiting a difference of 7 bars. EXAMPLE 4 - Improvement of the flux efficiency along membrane units in a 5-unit RO pressure vessel

A RO pressure vessel as shown in FIG. 7A was modeled. This model RO pressure vessel 700 includes four mimicries of spiral wound membrane units 702a-702d, and 704.

The concentration of feed water to each membrane element (for example, 702a-

702d, and 704 (FIG. 7A) along a pressure vessel is a function among others, of the element position along the vessel. Water productivity, term as water recovery, is limited by the net water drive which is a function among others, of the water concentration. At 50% water productivity the concentrate water at the exit of a vessel might get up to twice of the initial. The performance of peptoid bond membrane as a function of feed concentration was measured in a dead-end filtering apparatus in where the concentration of the solution in the feed tank, increases as permeate accumulated and the net pressure drive (external applied pressure minus osmotic resistance) decrease. Thus, less water flow across the membrane. Initial 32,000 ppm NaCl feed solution was used.

When using the chemical modified peptoid bound membranes in the unit 7004, the flux efficiency improves with the increase of the OPD along membrane units in the pressure vessel 700. The permeate water flow increases by for example, 18% in the first unit 702a, 22% in the second unit,702b, 29% in the third unit 702c, 42% in the fourth unit 702d and 85% flux flow increase in the fifth and last unit 704.

The chart in FIG. 7B details graphically the above permeate water flow improvements in the various units, showing the improvement of the flux when using the chemically modified membranes of EXAMPLE 2, compared with non-modified (baseline) membranes (detailed above) in increased concentration conditions along the units 704a-704d in the RO pressure vessel 700).

The improvement is determined by comparing the permeate water flux when using the chemically modified peptoid bound membranes (represented by line 730) of this invention to non-chemically modified peptoid bound membranes (represented by line 732).

The highest permeate water flux improvement, in percentages versus the non- chemically modified membrane, is achieved in the last membrane unit 704.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined by the appended claims and includes both combinations and sub-combinations of the various features described hereinabove as well as variations and modifications thereof, which would occur to persons skilled in the art upon reading the foregoing description.