Study on conformational transition phenomena of poly(methyl methacrylate) in acetonitrile near theta conditions

Abstract

The coil-globule transition for poly(methyl methacrylate);(PMMA) has been studied in a theta solvent, acetonitrile (theta =45 degreesC). The viscosity of PMMA was measured as a function of temperature in the range 26-55 degreesC. The contraction and expansion of the molecular chains are determined using the measured viscosity values. The temperature dependence of the intrinsic viscosity can be represented by a master curve in a alpha (3)(eta)\tau \M-W(1/2) (g(1/2) mol(-1/2)) versus \tau \M-w(1/2) (g(1/2) mol(-1/2)) plot, where tau = \T-theta\/T is the reduced temperature and M-w-is the weight-average molecular weight. A universal plot of reduced viscosity versus reduced blob parameter (N/N-c) shows the attainment of the collapsed state below the theta temperature. The dimensions of PMMA in acetonitrile (M-w = 3.15 x 10(6) g mol(-1)) decrease to 63 % at 26 degreesC of those in the unperturbed state. The results in this work are compared with those previously published. (C) 2000 Society of Chemical Industry.