Determination of Propagation Rate Coefficients by Pulsed-Laser Polymerization for Systems with Rapid Chain Growth: Vinyl Acetate

Abstract

The pulsed-laser polymerization (PLP) technique for determination of free radical propagation rate coefficients (kp) by gel permeation chromatography analysis has been extended to systems with rapid chain growth. A mathematical model is developed to gain a better understanding of the relative importance of propagation, termination, and transfer events on the laser-generated molecular weight distributions. Insights from the model are used to define appropriate PLP experimental conditions for vinyl acetate (VAc), for which measured kp values are an order of magnitude higher than values measured for styrene and methyl methacrylate at the same temperature. The behavior of VAc is contrasted with methyl methacrylate, both by experimental means and through simulation. Results suggest that VAc radicals not only propagate quickly but also have a higher rate of termination than methacrylate or styrene monomer systems, explaining the formation of broad, featureless molecular weight distributions under typical PLP experimental conditions. This work demonstrates the value of mathematical modeling to aid in the design of optimal PLP experiments.

Computer‐Aided Optimization of Conditions for Fast and Controlled ICAR ATRP of n‐Butyl Acrylate

“…However, several kinetic studies have indicated that the contribution of LCBs to the total amount of branches is very low, especially at low to intermediate conversions. [15,[19][20][21][22][23] In contrast to RP of ethylene and vinyl acetate in which the occurrence of chain transfer to polymer reactions is a long-standing fact that has been well documented since its discovery more than a half century ago, [24][25][26][27][28] the importance of branching in acrylate RP has only emerged in the early nineties by the detection of quaternary carbons via 13 C NMR spectroscopy. [29][30][31] Interestingly, Ahmad et al [32] have recently reported that the branching level of poly(nbutyl acrylate) can be reduced significantly by performing a CRP instead of an FRP.…”

Transient Behavior and Gelation of Free Radical Polymerizations in Continuous Stirred Tank Reactors

“…The propagation rate constant for the monomer is a recently measured value by PLP for vinyl acetate [42] and the values for ratios of constants relative to transfer to monomer, transfer to polymer, transfer to solvent, and propagation of terminal double bonds were taken from earlier works also dealing with vinyl acetate polymerization. [10,11,13] Termination is supposed to occur with equal probability by combination and by dismutation.…”

An improved general kinetic analysis of non-linear irreversible polymerisations

“…Kinetic parameters for this case study are presented in Table 14. The propagation rate constant for the monomer is a recently measured value by PLP for vinyl acetate (Hutchinson et al, 1994). Initiator decomposition rate constant and efficiency were taken as usual values for AIBN.…”