Orientation and relaxation study of miscible polystyrene/poly(vinyl methylether) blends

The macroscopic deformation and relaxation of orientation of miscible polys tyrene/poly(vinyl methyl ether) (PS/PVME) blends containing between 50 and 100% PS have been studied using polarization modulation infrared linear dic hroism (PM-IRLD). PS/PVME films were stretched at T-g + 15 to a draw ratio of 2, at constant draw rates of 10 and 100 cm/min. During the deformation, the addition of the lower molecular weight PVME to the blends leads to an i mportant increase of the orientation function of PS. During the relaxation period, a fast decay of the PS orientation function occurs at short times, followed by a slow chain relaxation at longer times. The relaxation rate is faster in pure PS than in the blends, the increase of the PVME content lea ding to a hindered relaxation. The orientation function of PVME is small in all cases, but we have been able, for the first time, to measure directly its relaxation, which follows closely the trend observed for PS. However, n o relaxation coupling can be clearly observed between the two polymers, the relaxation rate of PVME being always faster than that of PS. These results demonstrate the efficiency of PM-IRLD to determine quantitatively the time dependence of the orientation function of several chemical groups in multi component systems during the orientation and relaxation processes.