Patent ID: 6872514

Claim:
A polymer comprising recurring units each having a functional group of the following general formula (1), and having a weight average molecular weight of 1,000 to 500,000, wherein R 1 is a methylene group, oxygen atom, sulfur atom or SO 2 , R 2 to R 5 each are hydrogen, fluorine, a straight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, —R 6 —SO 3 R 7 or —R 6 —SO 2 R 7 , at least one of R 2 to R 5 containing —R 6 —SO 3 R 7 or —R 6 —SO 2 R 7 , R 6 is a valence bond or a straight, branched or cyclic alkylene or fluorinated alkylene group of 1 to 20 carbon atoms, R 7 is fluorine or a straight, branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms which may contain a hydrophilic group such as hydroxyl, and “a” is 0 or 1.