The dynamic Young's modulus, E, and birefringence of bisphenol A poly
carbonate were measured over the glassy to rubbery plateau zone. Measu
rements were performed over the frequency range of 1 to 130 Hz at vari
ous temperatures between 148 and 170-degrees-C. A modified stress-opti
cal rule was applied in characteristic analysis of the glassy and glas
s transition regions. It was earlier proposed to replace the stress-op
tical rule which, generally, was valid only at relatively low frequenc
ies corresponding to rubbery plateau and rubbery flow regions. E coul
d be separated into two component functions, E(R) and E(G)*. The stre
ss-optical coefficients,C(R) and C(G), associated with the respective
components were 5.0 x 10(-9) and 3.5 x 10(-11) Pa-1. In constructing m
aster curves of E(R) and E(G)* with the method of reduced variables,
an unlike temperature dependence was found. This result could account
for the breakdown of the time-temperature superposition principle for
E reported by several investigators.