Mesophase formation in isotactic polypropylene copolymers

Abstract

The main results related to the mesophase formation in the different isotactic polypropylene (iPP) copolymers are reviewed in this chapter. It is shown that fast scanning calorimetry (FSC) is mandatory for analyzing the process at the lower comonomer contents. On the contrary, the cooling rates required for the relatively high contents fall in the typical range of conventional DSC experiments, so that the mesophase development can be much more easily investigated (although there is an obvious decrease of the degree of order). Additionally, diffraction experiments under real time conditions (by means of synchrotron radiation) are also examined, which are used for establishing the specific character of the phases implicated. The main conclusion is that the cooling rates necessary for obtaining the mesomorphic state decrease progressively with increasing counit content, although important differences are reported depending on the comonomer type. Thus, it is shown that the content and size of the counit are influencing in a different way the rate of mesophase development and the transition temperatures. FSC experiments for studying the corresponding crystallization and mesophase rates of formation under isothermal conditions on iPP and copolymers are also reviewed.