Gel Formation and Molecular Characteristics of Poly(N‐isopropylacrylamide) Prepared by Free‐Radical Redox Polymerization in Aqueous Solution

The molecular characteristics of poly(N‐isopropylacrylamide) (PNIPA), prepared by free‐radical polymerization using an aqueous redox initiator and reaction conditions comparable to those used in the synthesis of nanocomposite gels, were investigated by altering the monomer concentration ([NIPA]) and the polymerization temperature (Tp) across the transition temperature (LCST). When Tp n*) above which PNIPA partially forms gels in the absence of a chemical crosslinker, and the gel fraction increases with increasing [NIPA] and decreasing Tp. In the range of n LCST, gels were not formed regardless of [NIPA]. The structure and mechanism of formation of self‐crosslinked PNIPA gels are discussed. magnified image