Modeling and Observer-Based Monitoring of RAFT Homopolymerization Reactions

Abstract

Reversible addition–fragmentation chain–transfer (RAFT) polymerization of methyl methacrylate (MMA) is modeled and monitored using a multi-rate multi-delay observer in this work. First, to fit the RAFT reaction rate coefficients and the initiator efficiency in the model, in situ 1 H nuclear magnetic resonance (NMR) experimental data from small-scale (<2 mL) NMR tube reactions is obtained and a least squares optimization is performed. 1 H NMR and size exclusion chromatography (SEC) experimental data from large-scale (>400 mL) reflux reactions is then used to validate the fitted model. The fitted model accurately predicts the polymer properties of the large-scale reactions with slight discordance at late reaction times. Based on the fitted model, a multi-rate multi-delay observer coupled with an inter-sample predictor and dead time compensator is designed, to account for the asynchronous multi-rate measurements with non-constant delays. The multi-rate multi-delay observer shows perfect convergence after a few sampling times when tested against the fitted model, and is in fair agreement with the real data at late reaction times when implemented based on the experimental measurements.

Model‐Assisted Optimization of RAFT Polymerization in Micro‐Scale Reactors—A Fast Screening Approach

“…Due to the complex underlying reaction mechanism of the RAFT polymerization, the kinetics of different systems were modeled in a number of studies in the past. [ 70–72,76,77,79–81 ] These models vary in their description of the reaction mechanism, but are mostly centered around two equilibria shown in Figure 2 and include five distinct polymer species (living, dormant 1–3 and deactivated).…”

“…The definition of the RAFT equilibrium used in the model is mainly based on two existing models. [ 71,80 ] The developed model was slightly adapted in the description of dormant chain 3 with an approach already used in another model, which is also implemented in Predici. [ 72 ] Dormant chain 3 has two different polymer chains connected to the RAFT agent.…”

“…Due to the relatively complex reaction mechanism and the promising possibilities of the RAFT polymerization method, this field has been addressed in many studies in the past. [ 69–81 ] A kinetic model has recently been used in combination with on‐line NMR spectroscopy to design a multi‐rate, multi‐delay observer to monitor the RAFT polymerization of methyl methacrylate (MMA). [ 80 ] This model is based on an older study [ 71 ] that was used to evaluate the performance of the same reaction in different reactor concepts.…”

“…[ 69–81 ] A kinetic model has recently been used in combination with on‐line NMR spectroscopy to design a multi‐rate, multi‐delay observer to monitor the RAFT polymerization of methyl methacrylate (MMA). [ 80 ] This model is based on an older study [ 71 ] that was used to evaluate the performance of the same reaction in different reactor concepts. In another study broaching the issue of modelling polymerization reaction kinetics, [ 72 ] the RAFT polymerization of styrene was investigated using the program package Predici.…”

Special Issue on “Computational Methods for Polymers”

“…Lathrop et al [9] report an experimental and theoretical/computational study on modeling and monitoring reversible addition-fragmentation chain-transfer (RAFT) polymerization of methyl methacrylate. They carry out parameter estimation to determine RAFT reaction rate coefficients and an initiator efficiency from in-situ 1 H NMR and SEC experimental data.…”