Effect of Intramolecular Transfer to Polymer on Stationary Free Radical Polymerization of Alkyl Acrylates, 2

Abstract

Summary: Procedures are developed to estimate kinetic rate coefficients from available rate data for the free radical solution polymerization of butyl acrylate at 50 °C. The analysis is based upon a complete mechanistic set that includes the formation of mid‐chain radicals through backbiting and their subsequent reaction, and contains no assumptions on how the rate coefficient for cross‐termination of mid‐chain and end‐chain radicals is related to the two homo‐termination rate coefficients. After a thorough statistical analysis, the results of the fitting are combined with other recent literature data to provide a complete set of individual rate coefficients for the butyl acrylate system. Monomer addition to a mid‐chain radical is estimated to be slower than addition to a chain‐end radical by a factor of more than 400. The termination of two mid‐chain radicals is estimated to be two orders of magnitude slower than termination of two end‐chain radicals, with the cross‐termination rate coefficient close to the geometric mean.Formation of a mid‐chain radical by intramolecular chain transfer to polymer by a chain‐end radical.imageFormation of a mid‐chain radical by intramolecular chain transfer to polymer by a chain‐end radical.

Multiscale Modeling of Branch Length in Butyl Acrylate Solution Polymerization

“…Short-chain and long-chain branching can affect chain overlap and entanglements by reducing the radius of gyration of polymer chains. To quantify the effects of branching on the radius of gyration, the intrinsic viscosity is calculated, using Equation (28)(29)(30)(31)(32) to determine the influence of long-chain branching, and Equation (33)(34)(35) to estimate the additional effect on [h b ] resulting from short-chain branching. As seen in Figure 9a, the intrinsic viscosity is most strongly influenced by the molecular weight, following a similar downward trend even when including the effects of branching.…”

“…The pre-exponential factors for the rate constants were obtained by fitting a steady-state model to literature data for solution polymerization of butyl acrylate at low conversion. [25,29] To simplify the notation in the rate-Equation model, all radical species propagating with rate constant k p are grouped into a single term [R tot ], and all live and dead species are combined into the term [P tot ]. The rates used in the rate-Equation model, taken primarily from Nikitin et al, [16] are given in Table 1.…”

EPR Analysis of n‐Butyl Acrylate Radical Polymerization

“…[6,15] To avoid such difficulties, continuous UV-irradiation has been applied to reach stationary radical concentrations.…”

Study of n-Butyl Acrylate Self-Initiation Reaction Experimentally and via Macroscopic Mechanistic Modeling

“…Macroscopic mechanistic modeling combined with adequate polymer sample measurements has proven to be a powerful tool to estimate the rate coefficients of individual reactions. Macroscopic mechanistic models have also been used extensively to estimate the rate coefficients of initiation by conventional thermal initiators, propagation, chain transfer and termination reactions in free-radical polymerization of acrylates [9,16,[27][28][29][30][31][32]. Kinetic parameters of several reactions in spontaneous thermal polymerization of n-BA under seemingly oxygen-free conditions (solvent was bubbled with nitrogen but not n-BA, and a nitrogen blanket was used inside the reactor) were estimated through detailed macroscopic mechanistic modeling, and the entire initiation was attributed to monomer self-initiation, leading to an unrealistically-large self-initiation rate coefficient [9].…”