Carbonated Water Mediated Preparation of Poly(N-isopropylacrylamide) Thermoresponsive Gels and Liquids

Carbonic acid solution was used a medium for the free radical polymerization synthesis of poly(N-isopropylacrylamide) (p-nipam) thermoresponsive polymer as an alternative to conventional inert gas purging. It was found that p-nipam cross-linked gels or linear liquids and p-nipam/dextran magnetite composite gels could be very rapidly prepared and large gels recovered intact from open air vessels. A porogen was necessary for high thermoresponse, and dextran use resulted in microporous composite gels that gave optimal thermal response at weight ratio of p-nipam:dextran of 4:1. Up to 82% weight loss was rapidly obtained upon warming above the lower critical solution temperature. Analysis of products was made by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), and superconducting quantum interference device (SQUID). A simplified and efficient overall method for preparation of biomedical polymers is shown. A wider application of H2CO3 solution as a viable alternative media and to allow open air aqueous polymerizations of water soluble or hydrophilic monomers is indicated.