On the influence of the supermolecular structure on structural relaxation in the glass transition zone: free volume approach

The idea of two miscellaneous amorphous fractions in polymer is discussed. The effect of free volume on the segmental relaxation behaviour is examined for a wide range of polymers. The orientation of the amorphous regions induced by semi- or liquid-crystallinity results in the appearance of constrained and unconstrained amorphous structures. In this paper, which better describes a relaxation, both types of amorphous fractions are distinguished. One fraction behaves as a bulky amorphous material ('real'), whereas the other one ('semi-ordered') behaves as a partially ordered structure. This results in two types of loss peaks interspersed along the temperature scale. The heights of both loss peaks are quite sensitive to the amount of free volume. alpha relaxation is deeply related to glass transition, although these two Phenomena are distinct. Differential scanning calorimetry, dynamic mechanical thermal analysis and positron annihilation were used to study the effect of specimen treatment on the assignment of the glass transition event associated with 'semi-ordered' amorphous phases. In a series of experimental studies of chain mobility and free volume, our attention has been given to elucidating the correlation between glass transition, a relaxation and the free volume of polymeric system.