Radiochemical studies of free radical vinyl polymerizations—IV. Polymerizations of esters of methacrylic acid

[¹⁴C]Azoisobutyronitrile has been used to initiate the polymerizations of methyl, ethyl, n-butyl, i-butyl, t-butyl, dodecyl, phenyl and cyclohexyl esters of methacrylic acid at 60°. Rates and efficiencies of initiation were measured and the mode of bimolecular termination of polymer radicals determined. Termination was predominantly by disproportionation in every case. No correlation could be found between n (the average number of initiator fragments per polymer molecule) and specific polar or steric effects for the ester groups but a possible correlation was detected between n and the ratio $\text{k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{/k}{}_{\mathrm{p}}$.