Determination of propagation and termination rate constants for some methacrylates in their radical polymerizations

Abstract

Abstract Rotating sector determinations of k p and 2 k t for ten methacrylates undergoing radical polymerization were carried out at 30°C. Ester groups in the monomers were: isopropyl, ethyl, β‐cyclohexylethyl, methyl, γ‐phenylpropyl, β‐phenylethyl, β‐methoxyethyl, benzyl, β‐chloroethyl, and phenyl. Values of k p obtained were 121, 126, 1190, 141, 149, 228, 249, 1250, 254, and 411 l./mole‐sec., respectively; values of 2 k t × 10 −6 were 4.52, 7.35, 32.8, 11.6, 0.813, 1.88, 9.30, 41.9, 6.71, and 11.9 l./mole‐sec., respectively. Omitting the data for the β‐cyclohexylethyl and benzyl esters, a Taft correlation, log k p = (0.70 ± 0.18)σ* + 2.2, was established, where σ* denotes Taft's polar substitutent constants for the above‐mentioned ester groups. The steric substituent constants E s were found to have no influence on k p . Combination of k p with r 2 data from copolymerization studies with styrene or methyl methacrylate as M 1 comonomer revealed that the more reactive monomer gave rise to the more reactive polymer radical. Monomer viscosities and molar volumes of the ester groups were found to correlate with 2 k t .