SYNTHESIS OF METHYL (Z)-2-METHYL-(3-D)PROPENOATES AND (E)-2-METHYL-(3-D)PROPENOATES AND THEIR INCORPORATION INTO POLYMETHACRYLATES

Methyl (E)- and (Z)-2-methyl(3-D)propenoates were prepared from (E)-3-bromo-2-methylpropenoic acid. Polymerization by free radical methods led to random incorporation, but anionic polymerization preserved labelling specificity, and the H-1 n.m.r. spectra of the labelled polymers confirm earlier assignments. Dimethyl 2,3-dimethylbutanoate was prepared by two new methods from dimethylmaleic anhydride and converted by anionic polymerization into a methacrylate polymer with a head-to-head linkage approximately in the centre of the chain. Thermal degradation of this polymer could only be achieved at temperatures so high that labelled monomers were themselves isomerized. Methacrylate polymers produced by anionic polymerization in the presence of diisopropylamine do not exhibit the isotacticity found with this form of polymerization.