Cross-linked porous membrane from hydrolysis of ester-containing side chain and preparation method thereof

A preparation method for a cross-linked porous membrane from hydrolysis of an ester-containing side chain, wherein the cross-linked porous membrane is prepared through hydrolysis of a copolymer of the ester-containing side chain in a presence of a micromolecule porogen under an alkaline condition;

• the copolymer of the ester-containing side chain is prepared by copolymerization of styrene, an ester-containing monomer, a vinylbenzyl chloride monomer and an azodiisobutyronitrile initiator;
• the ester-containing monomer comprises butyl methacrylate, ethyl methacrylate or propyl methacrylate;
• the micromolecule porogen is lithium chloride;
• alkalis in the alkaline hydrolysis condition are sodium hydroxide and potassium hydroxide;
• the chemical structural formula of the cross-linked porous membrane is shown below:
• the preparation method comprising the following steps:
• (1) synthesizing the copolymer
• dissolving sodium sulfonated styrene in solvent N,N-dimethylformamide at room temperature;
• respectively adding styrene, the ester-containing monomer, the vinylbenzyl chloride monomer and the azodiisobutyronitrile initiator under nitrogen protection;
• precipitating the obtained solution in a mixture of ethanol and water after reaction for 16-24 h at 50-80° C.;
• and washing the obtained precipitate with a detergent and drying at vacuum to obtain a yellowish granular product which is the copolymer,
• wherein the ester-containing monomer comprises butyl methacrylate, methyl methacrylate and ethyl methacrylate;
• and a molar ratio of the styrene to the ester-containing monomer to the vinylbenzyl chloride to the sodium sulfonated styrene to the azodiisobutyronitrile initiator is 0-35:50-85:12.5:2.5:0.1, wherein a concentration of the sodium sulfonated styrene solvent is 0.125 mmol/ml;
• and the detergent is the mixture of ethanol and water;
• (2) cross-linked membrane forming
• dissolving the polymer prepared in the step (1) in a solvent at room temperature;
• adding a cross-linking agent and the micromolecule porogen after dissolving;
• molar weights of the cross-linking agent and the micromolecule porogen being 12.5% and 7.5% of the molar weight of the polymer;
• generating a cross-linking reaction for 30-60 minutes at room temperature to obtain a mixture;
• dropwise adding the mixture to a glass plate;
• and drying to obtain a dense membrane,
• wherein a mass ratio of the polymer to the solvent is 3%-10%;
• and the solvent is N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide or N-methylpyrrolidone;
• and the cross-linking agent is tetramethyl hexamethylene diamine, and the micromolecule porogen is lithium chloride;
• (3) preparing the porous membrane through alkaline thermal hydrolysis
• stripping the dense membrane from a surface of the glass plate at room temperature, and placing the dense membrane in deionized water;
• taking out the dense membrane, placing the dense membrane in aqueous alkali of 4-6 M, and hydrolyzing for 7-12 days at 60-90° C.;
• flushing the hydrolyzed dense membrane with deionized water and then immersing the hydrolyzed dense membrane in the deionized water for 24-48 h until a surface of the membrane is neutral;
• immersing the membrane with a neutral surface in sulfuric acid solution of 1 M, and placing the membrane into the deionized water after 24 h for standby.