Studies of the amorphous region of polymers. II. Relationship between change of structure and glass-transition temperature in polycarbonate

A study of the effect of drawing on the glass transition temperature T_g of amorphous polycarbonate was carried out. The T_g attains a maximum at a draw ratio in the range from 1.6 to 2.0. The relationship between the change of structure and T_g is discussed in terms of the configurational entropy and the rate of molecular motion in local mode relaxation. The variation of T_g with drawing may be explained by using the iso-entropy theory. The frequency of the maximum in the dielectric loss f_max and the dielectric relaxation strength Δε of the β mechanism changed with drawing in the same way as that of T_g. Based on the parallel behavior in these results, it is reasonable to consider that the β process of local mode relaxation of polyesters such as PC and PET reflects the structure of the glassy state.