Crystal structure of isotactic poly(4‐methyl‐1‐pentene)

The crystal structure of isotactic poly(4‐methyl‐1‐pentene) was determined by x‐ray analysis. The unit cell is tetragonal, P4b2, with α = 18.70 Å and c (fiber axis) = 13.68 Å; it contains four molecular chains each consisting of seven monomeric units in the fiber period. The molecular conformation is essentially a (7/2) helix, but deviates slightly from the uniform (7/2) helix. The unusual low density is discussed from the structural point of view.