Viscoelasticity and Birefringence of Amorphous Polymers in the Glass Transition Zone

Abstract

Rheo-optical studies on viscoelasticity of amorphous polymers in the vicinity of the glass-to-rubber transition zone are reviewed. One of important progresses is a finding of the modified stress-optical rule, MSOR. The rule says that the stress has two molecular origins. One (R component) is due to the chain orientation like rubbery materials and the other (G component) is due to deformation of packing state of repeating units. The G component has common features for glass forming materials. The MSOR successfully explains many characteristic features of the viscoelasticity around the glass transition zone such as breakdown of time-temperature superposition principle. Another significance is that the MSOR provides a new method to analyze the viscoelasticity around the glass transition zone. The separation into the two origins gives better prospects on the relationship between viscoelasticity and the molecular structure. The method can be applied to other important issues including nonlinear viscoelasticity around the glass transition zone and sub-relaxations in the glassy zone.