ESTER METHYL-GROUP ROTATION IN POLY(METHYL METHACRYLATE) AND IN THE BLEND SOLUTION CHLORINATED POLYETHYLENE/POLY(METHYL METHACRYLATE) - A QUASI-ELASTIC NEUTRON-SCATTERING STUDY

Quasielastic neutron scattering (QNS) is employed to study the ester methyl group rotation in poly(methyl methacrylate) (PMMA) and, for the first time, in a solution chlorinated polyethylene/poly(methyl methacrylate) (SCPE/PMMA) blend. The QNS measurements for PMMA, SCPE and SCPE/PMMA were made in the temperature range 7-180, 17-290 and 40-290 K, respectively. and over the Q range 0.25-1.9 angstrom-1. Our results with respect to the bulk PMMA confirm the earlier assignment of the quasielastic broadening as being due to the ester methyl group rotation which persists at low temperatures, however, with decreasing intensity. Our results with respect to the phase separated-at 55 K above the cloud point curve-SCPE/PMMA blend revealed that blending of PMMA with SCPE produces a stronger effect on the O-CH3 population than a simple dilution. This is discussed in terms of the different mobilities of the two homopolymers which lead to an increase to the barrier to rotation and the proximity of the homopolymer chains in the blend.