ANALYSIS OF MODES OF PACKING OF THE MOST STABLE FORM OF SYNDIOTACTIC POLYPROPYLENE

Conformational energy calculations have been performed on the chain of syndiotactic polypropylene having s(2/1)2 symmetry with the aim to fi nd the best conformation in the crystalline field. A detailed packing analysis by molecular mechanics has been effected in order to clarify some features of the crystal structure of the most stable form. The cl ose packing is obtained along the direction of the b axis with chains having opposite chirality. A statistical arrangement of right-and left -handed chains is found in each site along the direction of the a axis . The results are in agreement with experimental data reported in the literature, and provide a satisfactory explanation of the discrepancie s present in previously proposed structures. (C) 1997 Elsevier Science Ltd.