
The present invention relates to materials which comprise a surface having pendant groups of formula (I), in which the groups --B-- are the same or different, preferably the same, and each is --CH.sub.2 -- or --C(.dbd.O)--, preferably --CH.sub.2 --, R.sup.1 is hydrogen alkyl of 1 to 12, preferably 1 to 4 carbon atoms, or a group capable of bonding to, or bonded to, a ligand or R.sup.1 is a polymerisable, preferably ethylenically unsaturated, group and Z is a zwitterionic group. Usually both grou...











