A polymer hydrogel comprisinga. a polymer according to formula (I)comprisingi. A polymeric unit (A) according to formula (II)ii. A crosslinking unit (B) comprising a spacer and at least a functional moiety F1 and functional moiety F2;b. and water,whereinn = 100 - 10,000, preferable 250 - 2500, more preferable 500 - 1500;m = independently 2-10, preferably 3 or 4.