Methyl acrylate polymerization kinetic parameters

The TR-SP-PLP technique enables the time-resolved measurement of the rate of polymerization by spectroscopically monitoring the decrease of the monomer concentration induced by one single laser pulse. Only when the conversion per laser pulse is reasonably high, time-resolved measurements are possible. The method is therefore limited to monomers with a reasonable high kp value (or a low kt value), including ethylene [3-5, 16-18], methyl acrylate [19], butyl acrylate [20-23] and dodecyl acrylate [19]. Recently, however, it has been extended to the methacrylates [24]. The relatively low conversion per pulse is actually also an advantage as it enables a high conversion resolution for the determination of kinetic parameters in these kinds of experiments. 

Unzueta et al. [18] derived a kinetic model for the emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA) employing both the micellar and homogeneous nucleation mechanisms and introducing the radical absorption efficiency factor for micelles, F, and that for particles, Fp. They compared experimental results with model predictions, where they employed the values of Fp=10 and Fn,=10", respectively, as adjustable parameters. However, they did not explain the reason why the value of Fp, is an order of magnitude smaller than the value of Fp. Sayer et al. [19] proposed a kinetic model for continuous vinyl acetate (VAc) emulsion polymerization in a pulsed... 

Unzueta and Forcada [31] studied the emulsion copolymerization of methyl methacrylate and n-butyl acrylate. It was assumed that both micellar nucle-ation and homogeneous nucleation are operative in this emulsion polymerization system. Based on the experimental data and computer simulation results, the values of the free radical capture efficiency factors for monomer-swollen micelles (f ) and polymer particles (Fj) that serve as adjustable parameters in the kinetic modeling work are approximately 1(T and 10, respectively. The reason for such a difference in the free radical capture efficiency factors is not available yet. Table 4.2 summarizes some representative data regarding the absorption of free radicals by the monomer-swollen micelles and polymer particles obtained from the literature. 

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