CRYSTALLINE ISOTACTIC TRANS-1,4-POLY(1,3-PENTADIENE) - EXPLANATION OF A STRESS-INDUCED CONFORMATIONAL TRANSITION

A conformational energy analysis is performed in order to explain the different conformations assumed by isotactic trans-1,4-poly(1,3-pentadiene) when crystallized under stretching conditions or not. The basic idea is that, while in an unstretched sample any configurational defect on the tertiary carbon atoms may be confined in the interlamellar region, stress-induced crystallization enhances the probability of configurational defects being embedded within an ordered environment. Results clearly indicate the cis-conformation as the most suitable to overcome conformational strains induced by defects in the crystalline phase, while the skew-conformation is preferred in an ordered environment.