An atactic liquid hydrocarbon homopolymer comprising irregular head-to-tail enchainment of randomly recurring units in the homopolymer backbone, said units having the structure ##STR12## wherein R2 is C1 -C20 alkyl or hydrogen and m is an integer of 1 to 100, said homopolymer having a bromine number between 1.5 and 10 and molecular weight between 1000 and 10,000.