Crystallization Kinetics and Morphology of the Mesomorphic Form of Syndiotactic Polypropylene

For the first time the kinetics of formation of syndiotactic polypropylene mesophase close to 0 8C through differential scanning calorimetry has been investigated. The calorimetric data have been analyzed through the well-known Avrami analysis. We have obtained Avrami coefficients less or at most equal to 2, which are likely to indicate a nearly bidimensionality of the crystallites. The morphology of the mesophase, not known up to now, has been examined through atomic forcemicroscopy (AFM): lamellar structures have been observed. The fractal dimension of the AFM images has been evaluated through the box counting method. It resulted about 2, in a very good agreement with the calculated Avrami coefficients. An infrared and diffractometer analysis on samples kept for increasing times at 0 8C has also been performed to confirm the calorimetric data. The experimental results allow one to better clarify the kinetics of mesophase-formation. It has been found that a time of 3 h at 0 8C is actually necessary for the complete crystallization of the trans-planar mesophase, a longer time is needed to stabilize the mesophase domains when the sample is extracted from 0 8C at room temperature