| Abstract: | Metallocene-based homogeneous Ziegler–Natta catalysts produce mono-olefin-terminated oligopropenes with narrow molecular weight distributions, controlled stereoregularities, and molecular weights ranging from 100 to 30,000 g/mole in high yield slurry and solution processes. Steric and molecular weight control are influenced by metallocene structures, and by polymerization conditions such as temperature and propene concentration. Predominantly mono-vinylidene-terminated oligopropenes are attractive intermediates, and feedstock for the synthesis of a variety of polypropylene materials, including blends, block and graft copolymers. The key step is the chain end functionalization of the vinylideneterminated oligopropenes via double bond conversion reactions, followed by the controlled synthesis of polypropylene block and graft copolymers. In melt and solution processes the olefinic end groups have been converted into a variety of polar functional groups, e.g. hydroxy, carboxy, succinic anhydride, thiol and acrylic groups. The thiol-terminated oligopropenes are chain transfer agents in radical methylmethacrylate polymerization with chain transfer constant measured to be 0.2. Acrylic monomers and styrene are grown onto the thiol end group via a chain transfer reaction, thus producing a family of block copolymers, e.g. poly(propene-b-methylmethacrylate) and poly(propene-b-styrene). As demonstrated by SEM fracture surface analysis, the poly(propene-b-styrene) block copolymers are efficient dispersing agents for compatibilizing polystyrene/polypropene (70/30) blends. Homo- and copolymerization of acrylic oligopropene macromonomers yield novel classes of graft copolymers with pendant isotactic or atactic oligopropene chains. Hydroxy-terminated oligopropenes are useful initiators in caprolactone polymerization to form poly(propene-b-caprolactone) block copolymers. IR spectroscopic studies demonstrate that succinic anhydride-terminated oligopropenes, obtained by ene-type addition of maleic anhydride to the olefinic oligopropene end group, react with oligomeric diamine-terminated polyamide-6,6 in the melt to yield polypropene-b-polyamide-6,6-b-polypropene triblock copolymers. |
