This work reports thermal and mechanical properties of a series of olefin copolymers synthesized by living coordination copolymerization of ethylene (E) and 1-hexene (H) with a fluorinated bis(phenoxyimine) titanium(IV) catalyst. The EH copolymers have ultrahigh molecular weights (UHMW), very narrow molecular weight distributions (MWD) and random distributions of ethylene and 1-hexene units along chain backbones. It is found that both high molecular weight and high 1-hexene incorporation give improved tensile properties, such as high modulus and excellent elasticity, in comparison to commercial polyolefin elastomers. Samples with M-w > 10(6) g/mol and F-2 > 25 mol% do not break even at an elongation of 1700%, and still have recoveries of >95%. An UHMW di-block copolymer containing a crystalline PE block and an amorphous EH block is also synthesized and compared. DSC, TEM and tensile tests reveal some interesting unique properties. (C) 2015 Elsevier Ltd. All rights reserved.