Design and Control of Copolymer Composition Distribution in Living Radical Polymerization Using Semi‐Batch Feeding Policies: A Model Simulation

Abstract

Summary: Although controlled/living radical copolymerization has been extensively studied, the control of copolymer composition distribution receives little attention. In this paper, taking RAFT copolymerization as an example, we develop a mathematical model and simulate copolymerization systems with various reactivity ratios. It is demonstrated that through semi‐batch operations with programmed profiles of slow monomer feeding rate, precise control over copolymer composition distribution (uniform and designed gradient distributions) along polymer chain can be achieved. It is also found that the semi‐batch operations have lower rates of polymerization than their batch counterparts. The reason for this difference is analyzed, and the magnitude depends on the reactivity ratios and targeted copolymer composition. The improvement of the semi‐batch rate by distributing a part of the initiator amount to the monomer feeding tank is found to be minor.

Fed-Batch Control and Visualization of Monomer Sequences of Individual ICAR ATRP Gradient Copolymer Chains

“…At higher conversions, this concentration drops, due to the volume increase upon monomer addition, and FRP behavior is thus circumvented leading to a good control over polymer properties. However, despite this excellent control, a relatively slow ICAR ATRP is obtained, in agreement with literature reports on related CRP systems [38,39]. It can thus be concluded that the highest linear gradient quality can be obtained using a multi-component fed-batch approach, as it allows tailor-design of linear gradient dormant copolymer chains albeit at the expense of an increase of the polymerization time.…”

“…For "normal" ATRP [38] and RAFT polymerization [39], such Mayo-Lewis based fed-batch additions were already explored with computer simulations, while assessing the overall conversion based on the number average chain length, i.e., assuming controlled conditions, and considering a monomer feed policy in which all of the less reactive comonomer is initially present and only the more reactive comonomer is added along the polymerization. However, in these kinetic studies, in which no explicit calculation of the copolymer composition is included, the fed/semi-batch addition of comonomer is accompanied by a low polymerization rate, a rather high dispersity and a relatively low livingness.…”

“…In this work, the ICAR ATRP fed-batch conditions are carefully selected to minimize the negative tendencies reported for related CRP systems [38,39]. First of all, simulations revealed that it is most suited to start the ICAR ATRP with a low monomer amount and add frequently small amounts of both comonomers under starved-feed conditions, i.e., at a constant high in situ conversion (e.g., >0.85) small amounts of both comonomers should be added in order to control the number of monomers added in between a single activation and deactivation.…”

Control of gradient copolymer composition in ATRP using semibatch feeding policy

“…In our previous article, we demonstrated by simulation that semibatch RAFT copolymerization with an appropriate monomer feeding policy offers effective control over the copolymer gradient profile. 27 In this work, we develop a kinetic model for semibatch ATRP copolymerization and investigate the effect of comonomer feeding policies on the gradient profile of resulting copolymers.…”

Modeling the Effects of Reactor Backmixing on RAFT Polymerization

“…Regarding the initiator concentration (see Figure 3c), the curve progression is similar when compared to the monomer concentration as increased backmixing gives higher initiator concentrations. This is reasonable as the consumption rate is proportional to the initiator concentration [Equation (16)]. Concentrations of consumed particles decrease gradually in a system of stirred tanks in series.…”