Crystallization of Isotactic Polypropylene under the Spatial Confinement Templated by Block Copolymer Microdomains

We investigate the crystallization behavior of isotactic polypropylene (iPP) under the influence of nanoscale confinement templated by the microphase-separated structure of an iPP-based diblock copolymer system, isotactic polypropylene-block-atactic polystyrene (iPP-b-aPS). Three types of iPP microdomains, i.e., lamellae, cylinder, and sphere, were generated by controlling the composition of the diblock. The effect of microdomain morphology on the nucleation mechanism, crystallization kinetics, self-nucleation behavior, the population of the helical sequence of iPP block in the melt state, and crystal orientation have been systematically studied. It was found that the crystallization rate of iPP was predominantly controlled by homogeneous nucleation when the crystallization process was largely confined within the individual cylindrical and spherical microdomains. Such a nucleation mechanism and the highly frustrated crystal growth in the isolated microdomains led to the absence of Domain II and atypical c...