Allyl-Terminated Polypropylene Macromonomers: A Routeto Polyolefin Elastomers with Excellent Elastic Behavior.

Wereport the design, synthesis, and physical/mechanical propertiesof graft copolymers containing semicrystalline polypropylene sidechains and amorphous ethylene/α-olefin copolymer backbones.These materials, a new class of semicrystalline, polyolefin-basedthermoplastic elastomers, are made in two steps. First, allyl-terminatedsyndiotactic or isotactic polypropylene macromonomers are synthesizedwith controlled microstructure and molecular weight using bis(phenoxyimine)titaniumor chiral ansa-zirconocene catalysts, respectively.Second, a pyridyl-amido hafnium catalyst is used to copolymerize themacromonomer, ethylene, and an α-olefin with precise controlof composition and side chain incorporation. With highly crystallinepolypropylene side chains and amorphous backbones of low glass-transitiontemperatures (<−55 °C), the samples have strain-to-breakvalues up to 1400% and elastic recovery above 85% at maximum strainsup to 1000%. The synthetic method described herein does not requirethe use of a living polymerization catalyst; in addition, the mechanicalproperties of these graft copolymers exceed those of the best linearblock polyolefins. [ABSTRACT FROM AUTHOR]