Methods for attaching polymerizable ceragenins to water treatment membranes using silane linkages

1. A method of attaching alkene-functionalized ceragenins to a surface of a polymer substrate using a silane-based coating and a Type-I compound, comprising, in the order listed:

a) applying a silane-based coating to a surface of a polymer substrate, wherein the coating contains free amine groups;

b) treating the silane-based coating with a Type-I compound comprising acid halides with an attached halogen atom that can be abstracted to leave a stable radical;

c) contacting the Type-I treated surface with a monomer solution comprising an alkene-functionalized ceragenin monomer, a comonomer, and a solvent;

d) adding a copper-based catalyst and a nitrogen-based ligand to the monomer solution contacting the surface, thereby initiating an atom-transfer radical polymerization (ATRP) reaction; and

e) forming ceragenin-containing copolymer reaction products that are chemically grafted to the surface of the polymer substrate via amide and siloxane linkages;

wherein no UV light is required to initiate the polymerization reaction.

2. The method of claim 1 , wherein the comonomer is an α,β-unsaturated carbonyl-type monomer; and the Type-I compound is 4-(chloromethyl)benzoyl chloride (CMBC) or bromoisobutyryl bromide; wherein 4-(chloromethyl)benzoyl chloride (CMBC) has the following structure:

and bromoisobutyryl bromide has the following structure:

3. The method of claim 1 , wherein the alkene-functionalized ceragenin is selected from the group consisting of CSA-105, CSA-113, CSA-109, and CSA-120; the Type-I compound is 4-(chloromethyl)benzoyl chloride (CMBC); the ceragenin comprises amine end groups that are protonated; the comonomer is selected from the group consisting of acrylamide, acrylic acid, acrylonitrile, methyl acrylate, methyl methacrylate, and maleic anhydride; and the solvent comprises a mixture of water and methanol.

4. The method of claim 1 , wherein the polymer substrate comprises a polyamide membrane.

5. The method of claim 1 , wherein the silane-based coating has a thickness ranging from 1 monolayer to 1 micron.

6. The method of claim 1 , wherein the polymer substrate comprises a polyethylene spacer; and wherein:

step a) comprises exposing the polyethylene spacer to an argon/oxygen plasma for at least 1-10 minutes, followed by exposing the spacer to air; immersing the spacer in a solution of 3-aminopropyltrimethoxysilane (APTMOS) in toluene (1 to 10 wt %) for at least 90 minutes at room temperature; and rinsing the spacer with toluene and then with ethanol;

step b) comprises contacting a surface of the spacer with a solution of 4-(chloromethyl)benzoyl chloride (CMBC) in dichloromethane (1 to 10 wt %), followed by heating the solution to reflux temperature for at least 20 minutes, then removing and washing the spacer with dichloromethane, and drying in air at room temperature;

step c) comprises adding a copper(I) bromide catalyst (1-25 weight % based on mass of monomers) and a 2,2′-bipyridine ligand (1-25 weight % based on mass of monomers) to the monomer solution;

step d) comprises allowing the polymerization reaction to proceed for at least 1 hour at room temperature, and rinsing the spacer with ethanol;

wherein a mole fraction of ceragenin in the monomer solution ranges from 2 to 100%, and a total monomer concentration ranges from 0.01 to 1 M; and

wherein no UV light is required to initiate the polymerization reaction.