| abstract |
A polymer comprising repeating units A and optionally repeating units B wherein Z=S, Se, N—R and O; W is at each occurrence independently a monocyclic or polycylic moiety optionally substituted with 1-4 R a groups; Y, at each occurrence, is independently a divalent C 1-6 alkyl group, a divalent C 1-6 haloalkyl group, or a covalent bond; c is from 1 to 6. |