thylene oxide repeat units and the molecular weight of the starting material (wherein all end groups are terminated by hydroxy groups) is about 1,040, [0120] wherein R1 and R2 each, independently of the other, is an alkyl group with from 1 to about 18 carbon atoms, [0121] wherein R1 and R2 each, independently of the other, is an alkyl group with from 1 to about 18 carbon atoms, and the like.