Scaling of the molecular weight-dependent thermal volume transition of poly(N-isopropylacrylamide)

Abstract

A series of narrowly distributed poly(N-isopropylacry-lamide) (PNIPAM) with molecular weight ranging from 8 × 104 to 2.3 × 10 7 g/mol were prepared by a combination of free radical polymerization and fractional precipitation. An ultrasensitive differential scanning calorimetry was used to study the effect of molecular weight on the thermal volume transition of these PNIPAM samples. The specific heat peak of the transition temperature (Tp.0) was obtained by extrapolation to zero heating rate (HR) because of the linear dependence of the transition temperature (Tp) on the HR. The relation between Tp.0 and the degree of polymerization (N) was investigated. © 2010 Wiley Periodicals, Inc.