Crystal structure of form III and the polymorphism of isotactic of poly(4-methylpentene)

A preliminary model for the crystal structure of form III of isotactic poly(4-methylpentene-1) is suggested on the basis of structure factor calculations. Chains in 41 helical conformations are packed in a tetragonal unit cell with axes a = 19.38 Å and c = 6.98 Å; the space group is I41. The polymorphic behavior of poly(4-methylpentene-1) is discussed on the basis of conformational energy calculations on the isolated chain. The presence of different modifications is in accordance with energy minima present in the conformational energy map. © 1994 American Chemical Society.