Temperature and microstructure dependence of the Rheo‐optical properties of polybutadienes

The present investigation covers the isothermal stress–strain–birefringence behavior of various polybutadienes between −30°C and 110°C. Birefringence measurements were also made under constant stress as a function of temperature in the low temperature region between −30°C and −120°C. The polybutadienes studied were two high cis ‐1,4 (prepared by different catalysts), a linear medium cis , and an emulsion polybutadiene. At temperatures at which the photoelasticity theory could be applied, the segmental polarizability anisotropy, its temperature dependence, and other parameters associated with an elastic polymeric network were determined. The influence of the degree of crosslinking was examined. At the low temperatures, microstructure was shown to have a pronounced effect on the photoelastic properties, the crystallization phenomena, and the glass–rubber transitions.