Abstract: The invention disclosed relates to novel branched chain hydroxy-terminated aliphatic azido polymers and copolymers with variable molecular weight (MW) and a single step method for the preparation thereof which involves respectively reacting a high (MW) 0.5-5.0.times.10.sup.6) solid rubbery polyepichlorohydrin (PECH) homopolymer and epichlorohydrin/alkylene oxide copolymer (PEEC), with an alkali metal azide in a suitable organic solvent, in the presence of an initiator at elevated temperature. The MW of the azido product may be controlled by including in the reaction mixture a basic degradation catalyst (such as LiOCH.sub.3 or NaOH) and varying the amount of catalyst. When the reaction is catalyzed, the MW of the product varies within the range 1,000-40,000 and the hydroxyl functionality is 2-10. Uncatalyzed reactions yield products with MW between 40,000 and 200,000 and a functionality of about 10.

Abstract: A castable polyurethane elastomer comprising the polymerization reaction product of a polyurethane prepolymer and 2,3-bis(hydroxymethyl) bicyclo [2,2,1] heptane as a chain extender. The elastomer has an advantageously low rebound property, which makes it particularly useful in shock absorber and anti-vibration mounting applications.