Computational Studies of RAFT Polymerization–Mechanistic Insights and Practical Applications

Abstract

Summary: Computational chemistry is a valuable complement to experiments in the study of polymerization processes. This article reviews the contribution of computational chemistry to understanding the kinetics and mechanism of reversible addition fragmentation chain transfer (RAFT) polymerization. Current computational techniques are appraised, showing that barriers and enthalpies can now be calculated with kcal accuracy. The utility of computational data is then demonstrated by showing how the calculated barriers and enthalpies enable appropriate kinetic models to be chosen for RAFT. Further insights are provided by a systematic analysis of structure‐reactivity trends. The development of the first computer‐designed RAFT agent illustrates the practical utility of these investigations.

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

“…Hitherto, high-level ab initio calculations [ 17,[34][35][36][37] and parameter estimation procedures based on more extensive kinetic modeling results [38][39][40][41][42] have been used to obtain these individual rate coeffi cients. Despite being based on fi rst principles, the former calculations often rely on calculations for smaller compounds to represent the considered system as a compromise between accuracy and computational cost, [ 15,37 ] whereas the parameter estimation methods highly depend on the elementary reactions considered in the kinetic model and the size of the polymerization data set. Care should thus be taken when adapting values for the addition and fragmentation rate and corresponding transfer coefficients from literature.…”

Living Radical Polymerization by the RAFT Process—A First Update

“…[5][6][7] Quiclet-Sire and Zard [8] have reviewed the application of radical addition-fragmentation processes in synthetic chemistry. Other reviews cover specific aspects of RAFT polymerization, such as computational studies related to RAFT agents and RAFT polymerization, [9] use of RAFT polymerization in heterogeneous media, [10,11] the synthesis of end functional polymers by RAFT polymerization, [12,13] the synthesis and properties of stimuli responsive block copolymers, [13] the preparation of honeycomb polymers, [14] Citation rate of our first communication [2] and first patent [3] on RAFT polymerization. Based on SciFinder search carried out in and the control of molecular weight distributions produced by RAFT polymerization.…”

“…[36][37][38][39] Buback and co-workers [37] have reported what they term the SP-PLP-ESR-RAFT technique where the rate of build-up and decay of the intermediate following radical generation is followed by EPR spectroscopy and analyzed to provide addition and (overall) fragmentation rates. Coote and co-workers [9,32,33,[40][41][42][43] have devised methods for calculating absolute values of K by applying ab initio methods. Values of K have also been estimated on the basis of simulation of the polymerization kinetics.…”

“…[39] The suitability of DFT methods for calculations relating to RAFT polymerization has been questioned. [9,41] The process of 'initialization', consumption of the initial low molecular weight RAFT agent, for styrene polymerization with cyanoisopropyl and cumyl dithiobenzoates at 70 • C has been compared using in situ 1 H NMR measurements. [51] The rate-determining step was found to be the rate of addition of the expelled radical (R • ) to styrene which was proposed to be faster for R • = cyanoisopropyl than for R • = cumyl.…”

First Principles Prediction of the Copolymerization Process of 1,3-Butadiene and Vinyl Chloride

“…That being said, in most cases to date the extent of that insight has been qualitative. These qualitative results include: the geometry of the transition state (TS) [4,5], which reaction mechanisms are most likely [6,7], and whether penultimate effects are negligible [8]. Only a hand full of polymer studies has reported quantitatively accurate results [9].…”