Crystal Structure of Form I of Syndiotactic Poly(para-methylstyrene)

The crystalline structure of form I of syndiotactic poly(para-methylstyrene) is described. In this form, the polymer chains assume a s(2/1)2 helical conformation and are packed according to the space group P2 1 /a in a unit cell with a = 24.5 A, b = 12.4 A, c = 8.1 A, and y = 143.5°. The proposed model may be described by a stacking of layers of alternating right- and left-handed helical chains efficiently packed in an "interdigital structure" in which phenyl rings belonging to one chain interlock with the phenyl rings of the two adjacent chains of opposite chirality. A disorder in the correct succession of the layers is suggested. A possible similarity between this form and the nanoporous 6 form of syndiotactic polystyrene, suggested by the fact they are both obtainable by guest removal from a class clathrates, is analyzed.