Synthesis of functionalized isotactic polypropylene dielectrics for electric energy storage applications

The structure-property relationship of isotactic polypropylene (f-PP) copolymers containing various comonomer units that change the semicrystalline morphology and increase dielectric properties was examined. The f-PP copolymers were prepared by the copolymerization of propylene with various comonomers, using both homogeneous and heterogeneous isospecific Ziegler-Natta catalysts. Both borane and silane functional groups were known to be stable in Ziegler-Natta catalysis systems, and the resulting borane- and silane containing PP copolymers were further interconverted into the corresponding OH containing polymers (III). The OH group content in the copolymer III was determined by the peak intensity and protons in the O-Si-(CH₃)₃ group of the copolymer II or the CH2-OH group of the copolymer III. The high molecular weight, characteristically tapered PP-OH copolymer (III); prepared by the heterogeneous Ziegler-Natta catalyst shows high crystallinity with a unique network structure, via interchain OH groups dimerization (H-bonding), offering high polarizability and good reversibility.