Evidence of Nodular Morphology in Syndiotactic Polypropylene from the Quenched State

The structure and morphology of samples of syndiotactic polypropylene (sPP) having different stereoregularity with concentration of rrrr pentads from 78 to 95.8%, crystallized by quenching the melt to 0 °C, is analyzed by wide-angle X-ray scattering and atomic force microscopy. The fast cooling from the melt induces the formation of nanocrystals of the trans-planar mesomorphic form of sPP resulting in a morphology characterized by the presence of globular entities (nodules) and absence of higher-order superstructures. It is shown that the nodule sizes depend on the stereoregularity of the sPP samples and the permanence time at 0 °C. The observed nodular morphology is completely different from the lamellar morphology typically obtained in sPP samples melt-crystallized at a lower cooling rate. This result indicates that crystals of different shape, size, and higher-order organization can be generated by changing the crystallization pathway.