Enhancing the Crystallization Behavior of Isotactic Polypropylene via Trace Amounts of Olefinic (Co)polymers

Two synthetic strategies were developed to prepare macromolecular nucleating agents: (i) in situ homopolymerization of olefin monomers (vinylcyclohexane (VCH), 7-octenyltrichlorosilane (OctCS), dichloro[bis(5-hexenyl)]silane (Hex 2 CS), and dichloro[bis(7-octenyl)]silane (Oct 2 CS)) during the prepolymerization of Ziegler–Natta(Z-N) catalysts; and (ii) their in situ copolymerization with propylene under identical catalytic conditions. Specially, copolymers of olefin monomer and propene were first used as nucleating agents for the i PP sample. The resulting Z-N catalysts, now functionalized with macromolecular nucleating agents, were subsequently employed to synthesize isotactic polypropylene ( i PP) via propylene polymerization. Subsequently, the nucleation efficiency of these macromolecular agents in the obtained i PP was systematically investigated to elucidate their impact on crystallization behavior and polymer properties. Notably, the incorporation of both homopolymer and copolymer nucleating agents significantly enhanced the crystallization temperature ( T c ) of the synthesized i PP samples, which increased to 118–127 °C─representing a maximum rise of 10 °C compared to neat i PP. Moreover, the polarized optical microscopy (POM) results revealed that the incorporation of macromolecular nucleating agents significantly accelerated the crystallization kinetics of i PP, yielding smaller and more uniform α-form spherulites compared to neat i PP. It is highlighted that structural and mechanical benefits conferred by optimized nucleating agents offer insights into the development of high-performance i PP materials.