Abstract: A fractionable elastic polypropylene which has an inherent viscosity of 1.5-9, exhibits no yield point, has a tensile set not exceeding 150% and contains about 10 to 80% by weight of a diethyl ether-soluble fraction having an inherent viscosity exceeding 1.50. This polypropylene is a direct reaction product and thus need not be separated into its component parts to be a useful elastomer. Also described is the diethyl ether-soluble polypropylene fraction of the direct reaction product which has about 0.5% to about 5% isotactic crystallinity and exhibits birefringence when a film formed from said fraction is viewed under crossed Nicol prisms in a polarizing microscope at about 25.degree. C. or is stretched between crossed polarizing sheets at about 25.degree. C. The diethyl ether-soluble fraction itself is a useful elastomeric material.

Abstract: A fractionable, elastomeric polymer of 1-butene consisting essentially of 30% to 80%, by weight, of an ether-soluble fraction having an intrinsic viscosity exceeding 1.5 and an infrared crystallinity value of about 1% to 15%; and 20% to 70%, by weight, of an ether-insoluble fraction having an infrared crystallinity value of about 20% to 55%; said polymer having an nmr isotacticity of about 20% to 50% and an intrinsic viscosity exceeding 1.5; elastomeric copolymers of 1-butene; polymer blends containing said elastomeric polymers; and a catalytic process for making said elastomeric polymers.