Radiopaque polymers

A hydrophilic polymer comprising pendent groups of the formula I:

• wherein:
• W is independently selected from —OH, —COOH, —SO3H, —OPO3H, —O—(C1-4 alkyl), —O—(C1-4 alkyl)OH, —O—(C1-4 alkyl)R2, —O—(C2H5O)qR1, —(C═O)—O—C1-4 alkyl and —O—(C═O)C1-4 alkyl, where —OH, —COOH, —O—PO3H and —SO3H may be in the form of a pharmaceutically acceptable salt;
• or a group —BZ;
• B is a bond, or a straight branched alkanediyl, oxyalkylene, alkylene oxaalkylene, or alkylene group, optionally containing one or more fluorine substituents;
• and
• Z is an ammonium, phosphonium, or sulphonium phosphate or phosphonate ester zwitterionic group;
• X is either a bond or a linking group having 1 to 8 carbons and optionally 1 to 4 heteroatoms selected from O, N and S;
• G is a coupling group through which the group of the formula I is coupled to the polymer and is selected from 1,3-dioxolane and 1,3 dioxane;
• R1 is H or C1-4 alkyl;
• R2 is —COOH, —SO3H, or —OPO3H2
• q is an integer from 1 to 4;
• n is an integer from 1 to 4;
• p is an integer from 1 to 3;
• and
• n+p is from 2 to 5.