Haupt‐ und seitenkettenkristallinität bei isotaktischen poly(1‐alkylethylen)en, 2. Röntgenographische, kalorimetrische und ramanspektroskopische untersuchungen am <i>it</i>‐poly(1‐eicosylethylen)

Abstract

Abstract Isotactic poly(1‐eicosylethylene) shows three polymorphic modifications. The orthorhombic modification I is formed during melt crystallization at a cooling rate ϕ&lt;2,5K.s −1 . The dimensions of the unit cell are calculated to be a =0,75 nm, b =8,8 nm and c =0,67 nm. The heat of fusion is 145J.g −1 , the melting point is 363K. The monoclinic modification II is crystallized from the polymer solution ( a =0,53 nm, b =10,8 nm, c =0,77 nm, β=94°). The heat of fusion amounts to 120J.g −1 , the melting point is 356K. Modification III is formed during rapid quenching of the melt. The side‐chains crystallized closely packed in layers. Modification III shows no main‐chain crystallinity. The heat of fusion is 40J.g −1 , the melting point is 348 K. The crystal field splitting in the Raman spectrum of modification +1418/1440cm −1 indicates an arrangement of the side‐chains as in orthorhombic polyethylene with two chains in the subcell. The subcells of both modifications II and III contain only one chain each.