AMORPHOUS PHASE AND INTERPHASE ORGANIZATION OF SYNDIOTACTIC POLYPROPYLENE

Materials prepared by syndiotactic polypropylene of different stereoch emistry (62 divided by 96% r pentads) undergo transitions in the cryst al phase, which depend on the thermomechanical history. The interfaces and the amorphous phase may be affected by the crystallite organizati on and the stereoregularity of the material. MAS NMR techniques provid ed a tool for characterizing the arrangement and the mobility of the p olymer chains in the inter-crystallite region. Chemical shifts, line-w idth and relaxation parameters were determined as a function of record ing temperature and glass transition temperature of the material. The same parameters were followed in the presence of a plasticizer. The di fferent degree of intimacy of the phases was established by following the diffusion of magnetization among the hydrogen atoms of the amorpho us and the crystalline phase. Defective regions and boundary regions w ere also identified and showed a large amount of conformations in the trans arrangement; the relaxation times indicate the chains being rigi d and intimately mixed with the crystalline phase.