Termination kinetics in free-radical bulk terpolymerization--the systems methyl acrylate-butyl acrylate-dodecyl acrylate and methyl methacrylate-butyl methacrylate-dodecyl methacrylate

摘要

Termination rate coefficients, k_t, for the terpolymerization of mixtures containing the three acrylates: methyl, butyl, and dodecyl acrylate or the corresponding members of the methacrylate family: methyl, butyl, and dodecyl methacrylate, have been measured via the single pulse (SP)-PLP technique. In the homopolymerization of each of the six monomers an initial plateau region of almost constant k_t is seen which extends at least up to 15% and, for dodecyl acrylate and dodecyl methacrylate, even up to about 50% monomer conversion. Terpolymerization k_t in this region of low and moderate conversion is remarkably well described by a rather simple correlation which exclusively contains homopolymerization k_t and the composition of the monomer mixture. This correlation turns out to be very useful for the modeling of k_t in mixtures of monomers that exhibit such an initial plateau region of k_t. For the systems under investigation, terpolymerization k_t may be estimated within +-30%. This finding is very remarkable in view of the enormous differences in homopolymerization k_t within each monomer family, e.g., k_t of methyl acrylate exceeds the corresponding dodecyl acrylate value by a factor of 50 (or 5000%). The entire set of experiments has been carried out at 40deg C and 1000 bar where the signal to noise ratio of the laser-induced single pulse experiments is very satisfactory. No reason is seen why the conclusions about modeling of terpolymerization k_t should not be valid at other reaction conditions including ambient pressure.