Intrinsic viscosity-molecular weight relationships for poly(n-isopropylacrylamide) solutions

Abstract

Poly(N-isopropylacrylamide) prepared by free radical polymerization was successfully fractionated into several fractions by using a carefully water-freed acetone as solvent and n-hexane as non-solvent. Based on the viscometric and osmometric studies of these fractions, the intrinsic viscosity-molecular weight relationships were determined as: [॑]=9.59 ȕ10-3 Mn0.65膕(in tetrahydrofuran at 27ŶC)and [॑]=14.5 ȕ10-2 Mn0.50膕(in aqueous solution at 20ŶC)These relationships imply that the statistical segment of poly(N-isopropylacrylamide) takes a considerably extended form in water than it does in tetrahydrofuran. It was also found that the aqueous solution exhibited an abnormal concentration dependence of viscosity at temperatures higher than 25ŶC and the phase separation at 30ŶC. © 1987 The Society of Polymer Science, Japan.