The atactic polystyrene (a PS) was slowly uni axial stretched at temperature 30℃ above its Tg.The resulting samples were characterized by a series of measurements.The results of IR dichroism

WAXD and optical birefringence all showed that in the segmental sense the samples were nearly isotropic

while the global orientation was remained

this can be indicated by the large elastic recovery of samples heated to temperatures above Tg.These samples showed large anisotropy in the solution swelling

the thermal expansion and stressstrain behavior.