Phase transformation in quenched mesomorphic isotactic polypropylene

The transformation of mesomorphic phase to a-monoclinic crystal phase in qu enched isotactic polypropylene has been investigated by TEM, DSC and time-r esolved SAXS and WAXD methods. It is found that even though the initial app earance of the cluster structure in mesomorphic i-PP seems to support the m odel of a multi-step process for polymer crystallization, results indicate that the transformation is not spontaneous. In the cluster domains, a signi ficant fraction of chain segments must undergo a reorganization process in order to establish the correct registration of helical hands for crystalliz ation. In addition, a fraction of the ordered chains with correct registrat ion of helical hands should also serve as primary nuclei to initiate crysta llization. However, the entire cluster domains should not be considered as 'precursors'. The growth process via secondary nucleation eventually transf orms the cluster structure to the lamellar structure. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.