A Combined Computational and ExperimentalStudy on the Free-Radical Copolymerization ofStyrene and Hydroxyethyl Acrylate

reserved4Bulk free-radical copolymerization of styrene and 2-hydroxyethyl acrylate (HEA) is investigated experimentally at 50 ° C using pulsed-laser polymerization and computationally using ab initio simulations. Arrhenius parameters for HEA chain-end homopropagation are A = 1.72 × 10 7 L mol − 1 s − 1 and E a = 16.8 kJ mol − 1 , based on experiments between 20 and 60 ° C. Copoly mer composition data are well fi tted by the terminal model with reactivity ratios r ST = 0.44 ± 0.03 and r HEA = 0.18 ± 0.04, but the variation in the propagation rate coeffi cient with monomer composition is underpredicted. Results are compared with computational predictions assuming the terminal as well as the penultimate unit effect (PUE) model. Intramolecular H-bonding is shown to have a signifi cant infl uence on PUE calculations. Discrepancies between computational predictions and experiment are attributed to the infl uence of intermolecular H-bonding.E. Mavroudakis ; K. Liang ; D. Moscatelli ; R. A. HutchinsonMavroudakis, Evangelos; K., Liang; Moscatelli, Davide; R. A., Hutchinso

Pulsed-laser and quantum mechanics study of n-butyl cyanoacrylate and methyl methacrylate free-radical copolymerization

Improved control over polymer microstructure is achieved by radical copolymerization of n-butyl cyanoacrylate with methacrylates.</p

Quantum Mechanical Investigation on Bimolecular Hydrogen Abstractions in Butyl Acrylate-Based Free Radical Polymerization Processes

The present computational study focuses on the investigation of bimolecular hydrogen abstractions that can occur during free radical polymerization (FRP) processes. In particular, several hydrogen abstractions from four monomers (butyl acrylate, BA; styrene, ST; butyl methacrylate, BMA; vinyl acetate, VA) and three different backbone chains (poly-BA, poly-BA-<i>co</i>-VA, and poly-BA-<i>co</i>-ST) have been studied. The aim is to provide an overview of the kinetics for all possible intermolecular hydrogen abstraction reactions from all chemical species present in a bulk FRP as well as to support the understanding of the influence of chemical environment on hydrogen abstractions. All simulations were performed using density functional theory (DFT) with quantum tunneling factors estimated using the Eckart model. This study provides proof that the presence of an electron donating group in the chemical environment of the abstracted hydrogen atoms can lead to lower activation energies and higher rate coefficients for abstraction whereas the presence of an electron withdrawing group leads to opposite effects

Theoretical Study of Chain Transfer to Agent Kinetics in Butyl Acrylate Polymerization

Reactions of chain transfer to agent (CTA) are conventionally used to regulate the polymer molecular weight during radical polymerization processes, due to the interaction between CTAs and chain-end growing radicals. In acrylate polymerization, the presence of a relatively large amount of midchain radicals (MCRs) opens the way for alternative kinetic pathways involving CTAs, which can result in a modification of the overall kinetics as well as the final polymer properties. In this work, chain transfer reactions from butyl acrylate (BA) radicals of various size and nature to a set of selected CTAs are investigated using quantum chemistry. The different reactivity of chain-end and midchain radicals is emphasized, with particular focus on the kinetic effect of the radical chain length. Eventually, the mechanism of MCR patching and its relevance in decreasing the branching density are critically examined, with reference to the estimated kinetic parameters and experimental evidence about BA polymerization