A composition, comprising: (a) at least one copolymer comprising repeating units of formula (I) wherein RA is a hydrocarbon group, optionally substituted with -OH, -SH, -COOH, NR'2, -COOR', -CONR', -CHO, with R' representing H or C1-3 alkyl, and with RA being selected such that the repeating unit of
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