o, alkoxy and alkylthio; or wherein R and R are as defined for R and R other than hydrogen; or together R and R collectively form a 5- to 6-membered ring wherein said ring may contain 0, N or S or halogen substituent; provided that at least one of R and R is other than hydrogen, said repeating unit (II) occupying 5 %--100% of said copolymer and wherein said polyurethane elastomer (b) is obtained b