| abstract |
A cyclic compound comprising m units of the formula Ia. n n n and n units of the formula (Ib) n n n joined together to form a ring, n wherein Y and y 2 are divalent bridging groups which may be the same or different in each unit; n R 0 is H or (C 1 -C 6 ) alkyl or is a metal or ammonium cation; n R 5 is H or (C 1 -C 60 ) alkyl or OH group; n j is 1 or 2; n R 3 is hydrogen, a hydrocarbyl or a hetero-substituted hydrocarbyl group; n each of R 1 , R 2 and R 4 , which may be the same or different, is hydroxyl, hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl, n with the provisos that n i) at least one of R 1 , R 2 , R 4 is hydroxyl, and m+n is 4 to 20, m is 1-8 and n is at least 3, and n ii) in formula Ia at least one OH group is in the meta or para position to the COOR 0 group and/or at least one R 5 group is OH. |