Modelling and kinetic study on radical polymerization of methyl methacrylate in bulk, 1. Propagation and termination rate coefficients and initiation efficiency

Abstract

In this work the exact data of the rate coefficients of propagation k , and termination k , , and initiator efficiencyfas well as their variations with conversion during the whole processes of the polymerization of methyl methacrylate in bulk have been measured using electron paramagnetic resonance (ESR) without any assumptions and approximations. k , was calculated directly from the synchronously measured data of the concentration of radicals and polymerization rate. k, was determined under nonsteady-state conditions by using the after-effect technique in the ESR measurement. f for the initiation with dimethyl 2,Zazoisobutyrate was evaluated from the initiation and termination rates. The ESR spectra show that the polymerization system is in a micro-heterogeneous state and there exist inactive radicals. A model of a diffusion-controlled reaction is proposed.

A Review of Modeling of Diffusion Controlled Polymerization Reactions

“…Further experimental results showed that initiator efficiency can dramatically change with monomer conversion. [43,44,48] It is worthy to mention here that, according to Figure 3, the initiator efficiency, f, starts dropping earlier than k p . [25] Besides MMA, the same phenomenon has also been experimentally observed for styrene.…”

“…Propagation involves the reaction of small monomer molecules and only one large radical, thus propagation is [43] Zhu et al [44] and Carswell et al [45] Near the glass point of the mixture, however, the value of k p begins to drop rapidly. [46] A qualitative picture of the variation of the propagation rate coefficient with conversion according to data presented in references [25,46] appears in Figure 3.…”

“…Shen et al, [43] based on experimental measurements using EPR, determined a value of f as a function of conversion during polymerization of MMA. The following expression was proposed accounting for diffusion and combination of the primary radicals in the ''cage'':…”

Chain Transfer in Degenerative RAFT Polymerization Revisited: A Comparative Study of Literature Methods

“…For simplicity, a constant conventional radical initiator effi ciency is assumed, which is a reasonable assumption for monomer conversions below 80%. [ 47,48 ] The RAFT exchange by degenerative transfer rate coeffi cients are varied for the evaluation of the various methods for a wide range of conditions. Chain length and conversion dependent apparent termination kinetics have been implemented explicitly via the k t,app ( n , x ) surface function reported by Derboven et al [ 8 ] at 353 K via the RAFT-chain length dependent-termination (RAFT-CLD-T) technique.…”

Initiation Kinetics in Free‐Radical Polymerization: Prediction of Thermodynamic and Kinetic Parameters Based on ab initio Calculations

“…[3][4][5][6] Such effect is empirically accounted through a suitable efficiency factor, usually estimated by direct fitting to experimental data. [7] If the Initiation kinetics in free radical polymerization is investigated using density functional theory. Thermodynamic and kinetic parameters of the initiation reactions are predicted, and the role of the initiators in the polymerization process is evaluated.…”