STRUCTURAL STUDY OF SYNDIOTACTIC POLYPROPYLENE GEL BY SOLID-STATE HIGH-RESOLUTION C-13 NMR

The molecular conformation and the phase structure of syndiotactic pol ypropylene gel were studied by infra-red and solid-state high resoluti on C-13 n.m.r. spectroscopies. It was found that the trans-trans-gauch e-gauche molecular conformation, that is most energetically stable in the bulk crystalline state of this polymer, is also formed in the gel. However, the methylene resonance lines of the gel observed in solid-s tate C-13 n.m.r. spectrum are somewhat different from that of the bulk crystal. The origin of this difference is attributed to a difference in the intermolecular interaction. The investigation of the phase stru cture revealed that the gel generally comprises three phases; the crys talline phase, noncrystalline amorphous phase, and crystalline-amorpho us interphase in a similar manner to the bulk crystals. About 64% of s olvent molecules in the gel are incorporated in the crystalline-amorph ous interphase as bound solvent and another 34% are in the amorphous p hase as free solvent. Copyright (C) 1996 Elsevier Science Ltd.