Polymerisable monomers and polymers

Compounds having a formula ##STR22## wherein:

• R.sup.1 to R.sup.4 may be the same or different and are selected from the group consisting of hydrogen, halogen, optionally substituted alkyl, optionally substituted aryl, nitrile, hydroxy, alkoxy, acyloxy and ester;
• or
• R.sup.1 and R.sup.2 or R.sup.3 and R.sup.4 together form methylene;
• X is selected from the group consisting of sulfur, sulfoxide, sulfone, disulfide and SO.sub.2 ;
• Y is selected from the group consisting of sulfur, oxygen, SO.sub.2, N--H, N-alkyl, N-aryl, acyl and
• CR.sup.5 R.sup.6 wherein R.sup.1 and R.sup.6 are the same as R.sup.1 to R.sup.4 ;
• and
• Z.sup.1 and Z.sup.2 are linking functionalities,
• wherein:
• Z.sup.2 is --G--(CRR).sub.p --J--, --G--(CRR).sub.p --O--(CO)--O--(CRR).sub.q --J--, --G--(CRR).sub.p --O--(CO)--(CRR).sub.q --J--, --G--(CRR).sub.p --O--(CRR).sub.q --J--, --G--(CRR).sub.p --C(.dbd.CH.sub.2)--(CRR).sub.q --J--, --G--(CRR).sub.p CO--(CRR).sub.q --J--, --G--(CRR).sub.p --(C.dbd.O)--J--, --G--(CRR).sub.p --S--(CRR).sub.q --J--, --G--(CRR).sub.p --SO.sub.2 --(CRR).sub.q --J--, --G--(CRR).sub.p --S--S--(CRR).sub.q --J--, or --G--(O--CRRCRR).sub.p --J--, wherein R may vary within the linking functionality and is hydrogen, alkyl, haloalkyl, hydroxyalkyl, hydroxy, carboxy, optionally substituted phenyl or halogen;
• or the group (CRR).sub.p represents carbonyl or optionally substituted phenylene, G and J are functional groups which join Z.sup.2 to Z.sup.1 and may be selected from the group consisting of a bond, --(CRR).sub.r, --O--, NH--, --S--, --(C.dbd.O)O--, --O--(C.dbd.O)O, --(C.dbd.O)NH--, and --NH--(C.dbd.O)--O--;
• and p, q and r are integers including zero.