Free radical copolymerization: an NMR investigation of current kinetic models

Abstract

The ability of terminal model kinetics to predict copolymer microstructure was tested for the styrenemethyl methacrylate system copolymerized at 40 O C at various fractions of monomers. NMR studies (in the accompanying paper) showed that previous peak assignments of the spectra of statistical styrenemethyl methacrylate copolymers were incorrect. The peak areas obtained for all copolymers were described in terms of triad sequences and were also adequately predicted by the terminal model utilizing reactivity ratios calculated from a nonlinear least squares fit to the copolymer composition data determined by 'H NMR. The nonterminal model behavior of the kinetics of the rate of polymerization described elsewhere can be successfully modeled by the 'restricted" penultimate model of Fukuda et al. We show that all current data can also be explained by various "bootstrap" or monomer-polymer complex models. Further model discrimination awaits new independent experimental results. IntroductionThe kinetic model that is most widely used to model free radical copolymerizations is the terminal model, also known as the Mayo-Lewis model.' For most copolymer systems the copolymer composition has been shown to be well fitted by the terminal model equation.2 Recently, however, there have been numerous reports of the inability

Study of free-radical copolymerization of acrylamide with 2-acrylamido-2-methyl-1-propane sulphonic acid

“…Higher order sequence distribution functions, in terms of conditional probability of AAm and AMPS centered triads, are calculated on the basis of monomer reactivity ratios, 19,20 and are shown in Figure 9(a,b). As expected, increasing the ratio [AAm]/[AMPS] increases the fraction of AAm H-NMR and 13 C-NMR spectra of AAm-AMPS copolymers are presented in Figure 10.…”

Statistical approach to model discrimination for the radical copolymerization of methyl methacrylate and styrene from a posteriori data of composition

“…These values are equal to original estimates given by the authors (1.5%). Maxwell et al [7] estimated for their composition data set the random error (precision) in the experimentally observed dependent and independent variables as 5% for copolymer composition (calculated from NMR peak areas) and 1% for the fraction in the feed. As argued above, for correct estimates of errors and a perfect model, the calculated values of standard deviation should be in the vicinity of 1 for MML.…”

“…Experimental data sets on radical copolymerization in bulk were those published by Fukuda et al [1] and Maxwell et al [7]. The first data set has already been proven to be accurate [8][9], with a sufficient number of experimental points and reliable estimates of error.…”

Solvent effects on the free-radical copolymerization of butyl acrylate with methyl methacrylate

“…2 method considering that the partition coefficient may be linearly dependent on copolymer composition. Maxwell et al 15) considered a "template" effect or "solvent-polymer complex" effect as a second way in which the local monomer concentration at the polymerization site may differ from that in the bulk phase and suggest an empirical formulation.…”