EVIDENCE OF 2 DIFFERENT CRYSTALLINE PHASES OF ISOTACTIC TRANS-1,4-POLY(1,3-PENTADIENE) - AN APPLICATION OF THE RIETVELD METHOD

ABSTRACT: An X-ray analysis has been performed according to the Rietveld whole-fitting method on a bulk-crystallized, annealed sample of isotactic trans-1,4-poly( 1,3-pentadiene). Calculated spectra have been obtained for different conformers in which the side methyl groups are in a cis or skew arrangement with respect to the adjacent double bonds. Comparison with the observed profile indicates that the skew conformation only gives a good agreement. This conclusion agrees with results already obtained by Neto et al. after a vibrational analysis of the same polymer. A comparison with intensities observed by Bassi et al. on an oriented fiber X-ray diagram shows however several major discrepancies. We deduce therefore the existence of two different crystalline phases that can be respectively observed in the bulk-crystallized polymer and in the sample stretched at a high temperature.