| abstract |
A cyclic compound comprising m units of formula (Ia) and n units of formula (Ib) joined together to form a ring, wherein Y and Y2 are divalent bridging groups which may be the same or different in each unit; R0 is H or (C¿1?-C6) alkyl or is a metal or ammonium cation; R?5¿ is H or (C¿1?-C60) alkyl or OH group; j is 1 or 2; R?3¿ is hydrogen, a hydrocarbyl or a hetero-substituted hydrocarbyl group; each of R?1, R2 and R4¿, which may be the same or different, is hydroxyl, hydrogen, hydrocarbyl or hetero-substituted hydrocarbyl, with the provisos that i) at least one of R?1, R2, R4¿ is hydroxyl, and m + n is 4 to 20, m is 1-8 and n is at least 3, and ii) in formula Ia at least one OH group is in the meta or para position to the COOR0 group and/or at least one R5 group is OH. |