Determination of the chain conformation of polypropylene in the crystalline state by neutron scattering

Abstract

Wide and small angle neutron scattering from melt-crystallised isotactic polypropylene mixtures of deuterated and protonated molecules were measured in aQ range of 0.003 A−1 to 0,8 A−1. The scattering curves between 0.1 A−1 and 0.8 A−1 are very sensitive to the amount of folding of the chains within a lamella. Different annealing conditions which influence the degree of crystallinit between 0.39 and 0.67 and the long spacing between 125 A and 245 A had an insignificant influence on the scattering in this range. For various arrangements of crystalline sequences scattering functions were calculated. Best agreement with the experimental scattering curves was obtained for a mixture of single and double crystalline sequences of equal proportion. An adjacent reentry folding model for the molecular conformation is not consistent with the experimental data.