Viscoelastic photoelastic behavior of copolymers of styrene and 2-methoxyethyl methacrylate. I. Random copolymers

Publisher Website
Google Scholar
Abstract
Viscoelastic photoelastic behavior of random copolymers of styrene (S) and 2-methoxyethyl methacrylate (MEMA) was studied in the main transition and rubberlike regions. With increasing content of MEMA in the copolymer the superimposed curves of both mechanical and optical functions at a constant temperature are shifted along the time axis towards shorter times. It has been shown that this shift is mainly due to an increase of free volume in the system with increasing content of MEMA. A comparison of photoelastic functions at corresponding states shows that both the width of the transition region and the number of entanglements decrease linearly with increasing weight content of styrene in the copolymer. A change of sign from positive to negative of the optical functions of copolymers (with the exception of PMEMA itself) was found in the main transition region. The anisotropy of the statistical segment Δα in the rubberlike region decreases linearly with molar content of styrene. A comparison of values of Δα for PMEMA and PS with values of the optical anisotropy of monomeric units Δω for their various models suggests that the side chain in MEMA can rotate freely, whereas the phenyl groups in styrene units remain in the transverse position regardless of the content of MEMA.