Whilst the compounds may be (alk)acrylamido compounds, that is in which A is NR1, in which case R1 is preferably hydrogen, or less preferably, methyl, most preferably the compounds are esters, that is in which A is O. In monomers of the general formula 1, especially where Y is the preferred (alk)acrylic group, B is most preferably an alkanediyl group.