Atom Transfer Radical Polymerization of Isobornyl Acrylate: A Kinetic Modeling Study

Abstract

A detailed kinetic modeling study of the atom transfer radical polymerization (ATRP) of isobornyl acrylate (iBoA) is presented. This study combines a detailed reaction scheme with a systematic approach to account for diffusional limitations. Calculated values for diffusion coefficients and the Williams-Landel-Ferry parameters for poly(iBoA) are based on rheological measurements. A good agreement with experimental data is obtained for the polymerization rate, average chain length, and polydispersity index in conditions ranging from 323 to 348 K for targeted chain lengths varying from 50 to 100 and initial activator/deactivator concentrations between 10-50/0-2.5 mol m -3 . In these conditions, βC-scission reactions are insignificant and backbiting reactions result in a slight decrease of the polymerization rate and level of control at high conversions only. Termination is subject to diffusional limitations during the whole ATRP, while diffusional limitations on deactivation cannot be neglected at higher conversion. Diffusional limitations are shown to be codetermined by the evolution of the chain length distribution of both the end-chain and mid-chain macromolecular species.

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

“…Based on [55] simulation results on the ATRP of isobornyl acrylate, [67] the cumulative CC double bond fraction is very low and can therefore be neglected in a first approximation. At high conversion, the cumulative branching fraction amounts to 0.015 corresponding to an average of five branches per polymer chain.…”

“…[15,[19][20][21][22][23] Similarly, termination by disproportionation [65,66] and addition reactions involving macromonomers are neglected in a first approximation. [67] The ATRP catalyst and initiator are the same as those used by Ahmad et al [32] in their experimental study of the bulk normal ATRP of nBuA at 378 K, i.e., CuBr/PMDETA and methyl 2-bromopropionate (MBrP). For the reactions common with FRP, intrinsic rate coefficients reported in literature are used.…”

“…The latter approach has been selected since simulations have revealed that a typical tenfold reactivity difference has no significant influence on the results. [55] The conversion profile and the evolution of the polymer properties with time are simulated using the methodology developed by D'hooge et al, [67,75] which is based on an extension of the method of moments coupled with an application of the quasi-steady state approximation for the calculation of population weighted apparent rate coefficients using a convergence test. CRP kinetic studies [75][76][77][78][79] have indicated that diffusional limitations can result in a lowering of the apparent termination reactivity during the polymerization and that deactivation can become diffusion controlled at sufficiently high conversion.…”

Kinetic Modeling of ICAR ATRP

“…Literature data were used to calculate the related individual apparent rate coefficients. [32][33][34][35][36][37][38][39] The chain length dependent apparent termination rate coefficients were calculated from the parameters obtained by the reversible addition fragmentation chain transfer-chain length dependent-termination (RAFT-CLD-T) method, with corrections for the presence of solvent. [32,33,40] For S, these parameters were determined at 363 K, however, as a first approximation, these values are also expected to hold at 353 K, the temperature used in this work.…”

“…[32,33,40] For S, these parameters were determined at 363 K, however, as a first approximation, these values are also expected to hold at 353 K, the temperature used in this work. For the other reaction steps, in which non-macromolecules are involved, the encounter pair model [34][35][36] was applied combined with the Vrentas and Duda free volume theory. [37] In particular, representative values were used in all simulations to describe the mobility of the deactivator.…”