wherein L is a linking group linking O and Q and Q is C(Z)???D wherein D is O or CR1R2 wherein R1 and R2 are independently H, alkyl or aryl and Z is H or C(Y)???O wherein Y is R3, OR3 or NR3R4 wherein R3 and R4 are independently H, alkyl or aryl and wherein any of L, R1, R2, R3 and R4 may be taken together to form a ring with the proviso that at least two of the A's in the polymer are QL. Usually