# US 10,766,005 B2 · Nanostructured polyelectrolytes for ion-selective membranes

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- Number: US 10,766,005 B2
- Document ID: US10766005B2
- Status: Granted
- Kind: B2
- Application number: 16/128,081
- Filed: 2018-09-11
- Published: 2020-03-12
- Granted: 2020-09-08
- Earliest claimed: 2018-09-11
- Assignees: National Technology & Engineering Solutions of Sandia, LLC
- Applicants: National Technology & Engineering Solutions of Sandia, LLC
- Inventors: Leo J. Small; Stephen Percival; Erik David Spoerke
- Web page: https://patentgrep.com/patent/US10766005B2

## CPC

- B01D 61/445: {with bipolar membranes; Water splitting}
- B01D 61/461: {comprising only a single cell, only one anion or cation exchange membrane or one pair of anion and cation membranes}
- B01D 69/02: characterised by their properties
- B01D 69/1216: {Three or more layers}
- B01D 69/125: {In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction}
- B01D 71/401: {Polymers based on the polymerisation of acrylic acid, e.g. polyacrylate}
- B01D 71/601: {Polyethylenimine}
- B01J 43/00: Amphoteric ion-exchange, i.e. using ion-exchangers having cationic and anionic groups; Use of material as amphoteric ion-exchangers; Treatment of material for improving their amphoteric ion-exchange properties (ion-exchange chromatography processes B01D15/36)
- C08J 3/245: {Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking}
- C08J 5/2256: {based on macromolecular compounds obtained by reactions other than those involving carbon-to-carbon bonds, e.g. obtained by polycondensation}
- C08J 5/2287: {After-treatment}
- C08J 7/042: {with two or more layers, where at least one layer of a composition contains a polymer binder}
- B01D 2323/30: Cross-linking
- B01D 2325/14: Membrane materials having negatively charged functional groups
- B01D 2325/16: Membrane materials having positively charged functional groups
- B01D 2325/42: Ion-exchange membranes
- C08J 2333/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof
- C08J 2369/00: Characterised by the use of polycarbonates; Derivatives of polycarbonates
- C08J 2379/02: Polyamines
- C08J 2433/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof
- C08J 2479/02: Polyamines
- C09D 133/04: Homopolymers or copolymers of esters {(C09D143/04 takes precedence)}
- C09D 179/02: Polyamines
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)

## Abstract

Nanostructured polyelectrolyte bilayers deposited by Layer-by-Layer deposition on nanoporous membranes can be selectively crosslinked to modify the polyelectrolyte charge density and control ionic selectivity independent of ionic conductivity. For example, the polyelectrolyte bilayer can comprise a cationic polymer layer, such as poly(ethyleneimine), and an anionic polymer layer, such as poly(acrylic acid). Increasing the number of bilayers increases the cation selectivity when the poly(ethyleneimine) layer is crosslinked with glutaraldehyde. Crosslinking the membranes also increases the chemical and mechanical strength of the polyelectrolyte films. This controllable and inexpensive method can be used to create ion-selective and mechanically robust membranes on porous supports for a wide range of applications.

## Claims

### Claim 1

A method to fabricate an ion-selective membrane, comprising the steps of:
providing a nanoporous membrane; and
layer-by-layer depositing at least one polyelectrolyte bilayer on at least one side of the nanoporous membrane, wherein the polyelectrolyte bilayer comprises a cationic polymer layer and an anionic polymer layer; and either
chemically crosslinking or charge-neutralizing the cationic polymer, thereby decreasing a cationic fixed charge in the polyelectrolyte bilayer; or
chemically crosslinking or charge-neutralizing the anionic polymer, thereby decreasing an anionic fixed charge in the polyelectrolyte bilayer; or
chemically crosslinking the cationic polymer with the anionic polymer, thereby decreasing both a cationic fixed charge and an anionic fixed charge in the polyelectrolyte bilayer.

### Claim 2 (depends on 1)

The method of claim 1, wherein the cationic polymer comprises an amine group.

### Claim 3 (depends on 2)

The method of claim 2, wherein the amine group comprises a primary or quaternary amine group.

### Claim 4 (depends on 2)

The method of claim 2, wherein the chemically crosslinking comprises crosslinking the amine groups of the cationic polymer with an amine-reactive crosslinker to form amine-to-amine bonds.

### Claim 5 (depends on 1)

The method of claim 1, wherein the anionic polymer comprises a carboxylic acid group or sulfonate group.

### Claim 6 (depends on 5)

The method of claim 5, further comprising charge-neutralizing the carboxylic acid groups of the anionic polymer with carboxylate-reactive agent.

### Claim 7 (depends on 1)

The method of claim 1, wherein the cationic polymer comprises an amine group and the anionic polymer comprises a carboxylic acid group.

### Claim 8 (depends on 7)

The method of claim 7, wherein the chemically crosslinking comprises crosslinking the amine groups of the cationic polymer with the carboxylic acid groups of the anionic polymer to form amide bonds.

### Claim 9 (depends on 8)

The method of claim 8, wherein the amine groups of the cationic polymer are chemically crosslinked with the carboxylic acid groups of the anionic polymer with a carbodiimide crosslinker.

### Claim 10 (depends on 7)

The method of claim 7, wherein cationic polymer comprises poly(ethyleneimine) and the anionic polymer comprises poly(acrylic acid).

### Claim 11 (depends on 10)

The method of claim 10, wherein the chemically crosslinking comprises crosslinking the amine groups of the poly(ethyleneimine), thereby decreasing a cationic fixed charge in the polyelectrolyte bilayer.

### Claim 12 (depends on 11)

The method of claim 11, wherein the poly(ethyleneimine) is crosslinked with glutaraldehyde.

### Claim 13 (depends on 10)

The method of claim 10, further comprising wherein the chemically crosslinking comprises crosslinking amine groups of the poly(ethyleneimine) with carboxylic acid groups of the poly(acrylic acid).

### Claim 14 (depends on 13)

The method of claim 13, wherein the poly(ethyleneimine) and the poly(acrylic acid) are crosslinked with N-(3-dimethylaminopropyl)-N′-ethylcarbodimide hydrochloride.

### Claim 15 (depends on 1)

The method of claim 1, where the at least polyelectrolyte bilayer comprises at least three polyelectrolyte bilayers.

### Claim 16 (depends on 1)

The method of claim 1, wherein the layer-by-layer depositing step comprises sequential dip coating of the cationic polymer layer and the anionic polymer layer.

### Claim 17 (depends on 1)

The method of claim 1, wherein the cationic polymer or anionic polymer or both further comprises at least one biomolecule.

### Claim 18 (depends on 17)

The method of claim 17, wherein the at least one biomolecule comprises an amino acid or peptide.