Isotactic Polypropylene-Based Stereoregular Diblock Copolymers: Syntheses and Self-Assembly

The preparation of polyolefin-based stereoregular diblock copolymers (BCPs) by postpolymerization of hydroxy-capped isotactic polypropylene (iPP) led to the successful generation of a series of structurally well-defined iPP-based stereoregular BCPs for self-organizing into various nanostructures. The hydroxy-capped iPP prepolymer was synthesized by using ansa-metallocene catalysts to mediate the selective chain transfer to alkylaluminums during isospecific polymerization of propylene, leading to the production of alkylaluminum end-capped iPP as the preliminary product. Subsequently, in-situ 02/1-1202 treatment of the resulting aluminum-capped iPP led to the successful preparation of hydroxy-capped iPP. The terminal hydroxyl end group of the iPP-based prepolymer was allowed to undergo tosylation reaction that led to the production of tosyl group end-capped iPP with a quantitative functional group conversion ratio. Subsequently, coupling the tosyl group end-capped iPP with living anionic poly(2-vinylpyridine) (P2VP) provided a series of structurally well-defined iPP-based BCPs. Various microphase-separated nanostructures can be obtained by taking advantage of the synthesized stereoregular BCPs for self-assembly. Furthermore, an interesting phase transformation from cylinder phase with hexagaonal packing to gyroid phase with bicontinuous structure can be induced by shearing the samples at the ordered melt state.