| abstract |
A copolymer including a repeating unit represented by (I) wherein: Y is selected from: a carboxylic acid, sulfonic, phosphorous acid and phosphoric acid and their corresponding salt or ester; imino, amide, nitrile, hydrogen, hydroxyl and alkyl comprising from 1 to 6 carbon atoms; and R 1 , R 2 , R 3 , and R 4 are independently selected from: hydrogen, alkyl groups comprising from 1 to 6 carbon atoms, and R 1 and R 2 may collectively form a ketone group or a 9, 9' -fluorene group, and R 3 and R 4 may collectively form a ketone group or a 9, 9' -fluorene group; R 5 and R 6 are independently selected from: a bond and an alkylene group comprising from 1 to 6 carbon atoms; R 7 is selected from: hydrogen, alkyl, aryl, aralkyl and heteroaryl groups comprising from 1 to 8 carbon atoms which may be unsubstituted or substituted with carboxylic acid, sulfonic acid and phosphoric acid and their corresponding salt or ester, imino and amide; and X and X' are independently selected from: a carboxylic acid, sulfonic acid and phosphoric acid and their corresponding salt or ester, imino and amide; nitrile, hydrogen, alkyl having from 1 to 6 carbon atoms and alkoxy having from 1 to 6 carbon atoms. |