Structural organization of syndiotactic polypropylene films quenched at different temperatures

Films of highly syndiotactic polypropylene (sPP) were quenched at different temperatures between 0 degrees C and 100 degrees C and analyzed as soon as prepared and after 1 month of aging at room temperature. Wide-angle X-ray diffractograms (WAXDs) showed that all the samples crystallized in the diso rdered helical form I, with the crystallinity increasing both on increasing the quenching temperature and on aging, although to a lower extent. The an alysis of sorption and diffusion of dichloromethane vapor at low activity s hows that, in some samples, the fraction of impermeable phase is consistent ly higher than the crystalline fraction. This induced us to hypothesize the presence of an intermediate phase, or mesophase, not crystalline, yet impe rmeable to the vapors. The fraction of mesophase decreases on increasing th e quenching temperature, and it is a very small quantity at 100 degrees C. The dynamic-mechanical analysis showed two transitions in the aged samples, which could correspond to the lower and upper glass transitions, already s uggested for aged films of isotactic polypropylene (IPP).