CONFIGURATIONAL-CONFORMATIONAL STATISTICS OF ATACTIC POLYPROPYLENE

The configurational-conformational characteristics of polypropylene are discussed by considering every polymer chain as constituted by the periodic repetition of a sequence of monomeric units in a given configuration. Sample calculations are presented for the special case in which meso and racemic dyads are distributed according to Bernoullian statistics. Numerical results show that the characteristic ratio of atactic polypropylene reaches an asymptotic value of 5.34 when the size of the periodic sequence corresponds to six monomeric units. The temperature coefficient is calculated to be - 1.34 x 10(-3) K-1, in good agreement with experimental data reported in literature. The characteristic ratio of the mean-square radius of gyration, [R(g)2]/nl2, obtained from our calculations for the atactic polymer is 0.86. The effect of the fraction of meso dyads in Bernoullian polypropylene chains on the conformational and configurational entropy is also evaluated.