This invention relates to high melting
polyolefin copolymers suitable as
thermoplastic elastomers and catalysts and methods for their synthesis. These elastomeric olefin copolymers are characterized by a
mole fraction of crystallizable component Xc from about 30 to about 99%; low
glass transition temperatures, below -20° C., and typically below -50° C.; melting points above about 90° C.; high molecular weights; a molecular
weight distribution MW / Mn< / =10; and a narrow composition distribution between chains of < / =15%. The novel copolymers of the invention range from reactor blends to multiblock copolymers that can be sequentially fractionated into fractions of differing crystallinities, which fractions nevertheless show compositions of comonomers which differ by less than 15% from the parent
polymer (reactor product). The invention also relates to a process for producing such copolymers by utilizing an unbridged, substituted or unsubstituted cyclopentadienyl
metallocene catalyst that is capable of interconverting between states with different copolymerization characteristics, which interconversion is controlled by selecting the substituents of the cyclopentadienyl ligands so that the rate of interconversion of the two states is within several orders of magnitude of the rate of formation of a single
polymer chain. Where ri>rf the
polymer can be characterized as multiblock; where ri<rf, the result is a
polymer blend and where ri / rf is close to 1, the resulting polymer is a mixture of blend and multiblock. The
metallocene catalysts of the invention are able to interconvert between more than two states, with embodiments of four states being shown in FIG. 2.