Molecular orientation relaxation in binary blends of poly(methyl methacrylate) by rheo-optical Fourier-transform infrared spectroscopy

Abstract

Rheo-optical Fourier-transform infrared spectroscopy, a technique combining simultaneous mechanical measurements and infrared dichroism spectroscopy, has been employed in order to investigate the molecular chain orientation and orientation relaxation behaviour in uniaxially stretched films of binary blends of long perdeuterated and short undeuterated chains of linear poly(methyl methacrylate) (PMMA). The solution cast film samples have been stretched at constant strain rate up to 100% elongation and subsequently allowed to relax at constant strain at various temperatures above the glass transition temperature. The results reported here show that for the short-chain component a threshold value of molecular weight exists below which a drastic decrease of the long- and short-chain orientation and a change in the relaxation behaviour of the short chains are observed.