POLYESTER HYDROGELS

The present invention relates to a polyester comprising units derived from monomers A, B and C, wherein the group of monomers A consists of (a1) monomers A1, or (a2) monomers A1 and monomers A2, with monomers A1 and monomers A2 being present in a molar ratio of at least 31:69, preferably at least 4:1, wherein the monomers A1 are selected from the group consisting of aromatic sulfonated dicarboxylic acid based monomers of general formulae (I), (II), (III) and (IV), and wherein the monomers A2 are selected from the group consisting of non-sulfonated aromatic dicarboxylic acid based monomers of general formulae (V), (VI) and (VII); and wherein the group of monomers B consists of (b1) monomers B1, or (b2) monomers B1 and monomers B2, with monomers B1 and monomers B2 being present in a molar ratio of at least 1:9, preferably at least 4:1, wherein the monomers B1 are selected from the group consisting of unsaturated dicarboxylic acid based monomers of general formula (VIII), and wherein the monomers B2 are selected from the group consisting of saturated dicarboxylic acid based monomers of general formula (IX); and wherein the group of monomers C consists of (c1) monomers C1, (c2) monomers C2, or (c3) monomers C1 and C2, wherein the monomers C1 are selected from the group consisting of ethylene glycol based monomers of general formula (X), and wherein the monomers C2 are selected from the group consisting of propylene glycol based monomers of general formula (XI), and wherein the molar ratio of the units derived from the group of monomers A to the units derived from the group of monomers B is from 9:1 to 1:2.4, and wherein the molar ratio of the units derived from the groups of monomers A and B to the units derived from the group of monomers C is from 1.3:1 to 1:1.3. The polyester of the invention is preferably cross-linked.