Radical Lifetimes in Atom Transfer Radical Polymerization: A Monte Carlo and Deterministic Investigation

Abstract

Mean radical lifetimes and fluctuations in lifetime are shown to decrease with conversion and polydispersity index for atom transfer radical polymerization (ATRP) of both methyl methacrylate and styrene. In the first study of its kind, a comprehensive investigation of radical lifetimes in both ATRP and conventional free-radical polymerizations is reported using a kinetic Monte Carlo model. Quantile−quantile plots show the radical lifetimes to be exponentially distributed with equal mean and standard deviation. Radical lifetimes are shown to be thousands of times longer in conventional free-radical polymerization compared with ATRP. Reduced mean radical lifetimes and fluctuations offer a new perspective on the ATRP mechanism. Reduction in radical lifetime fluctuations ensures less variability in the number of monomer units added during the propagation steps and keeps the polydispersity index low. Deterministic models are used along with the kinetic Monte Carlo model to investigate several facets of these polymerization systems and are validated against experimental data.

Benchmarking Stochastic and Deterministic Kinetic Modeling of Bulk and Solution Radical Polymerization Processes by Including Six Types of Factors Two

“…In PRE, one of the most studied processes is solution/bulk conventional or free radical polymerization (FRP). [ 38–45 ] The core FRP reactions are displayed in Figure a, focusing on homopolymerization utilizing I 2 as conventional radical initiator and M as monomer. At elevated temperature, I 2 dissociates to form an initiator radical I that reacts with one monomer molecule through so‐called chain initiation to obtain a macroradical of chain length 1 ( R 1 ).…”

“…[31,[34][35][36][37] In PRE, one of the most studied processes is solution/ bulk conventional or free radical polymerization (FRP). [38][39][40][41][42][43][44][45] The core FRP reactions are displayed in Figure 1a, focusing on homopolymerization utilizing I 2 as conventional radical Bulk and solution radical polymerization is important in daily live. A challenge is still to maximize polymerization rate and control over molecular characteristics such as the molar mass distribution.…”

Roadmap for Monomer Conversion and Chain Length-Dependent Termination Reactivity Algorithms in Kinetic Monte Carlo Modeling of Bulk Radical Polymerization

“…This means that the apparent termination rate is based on larger radicals, resulting in a lower < k t,app > value and thus a slightly higher (strictly incorrect) monomer conversion. In contrast, at higher monomer conversions, the calculation method for < k t,app > becomes less relevant as the NMP becomes more and more controlled due to the well-established persistent radical effect, , greatly reducing the radical concentration and thus the relevance of termination reactions also as with increasing average chain length diffusional limitations are more pronounced. , …”

“…In contrast, at higher monomer conversions, the calculation method for <k t,app > becomes less relevant as the NMP becomes more and more controlled due to the well-established persistent radical effect, 107,108 greatly reducing the radical concentration and thus the relevance of termination reactions also as with increasing average chain length diffusional limitations are more pronounced. 50,109 The dormant polymer CLD is additionally shown in Figure 3(e) at three monomer conversions: 5, 30, and 60%. Since the radical concentrations are very low, we opted to plot the CLD for the dormant chains as active radicals are generated almost exclusively out of this population and radical MC profiles are not free from noise unless extremely large initial numbers of molecules are selected.…”

Glycopolymer-Based Materials: Synthesis, Properties, and Biosensing Applications

“…The active (propagating) radical concentration is low enough to reduce the contribution of radical–radical termination, which can occur through radical coupling or disproportionation due to this shift. At the same time, quick initiation and deactivation with low stationary radical concentrations are essential for extending the life span of polymer chains, resulting in improved control over the final polymer [ 57 ]. Zhao et al, for example, presented the ATRP approach for the synthesis of dextran- g -poly (2-dimethylaminoethyl methacrylate- co -2-lactobionamidoethyl methacrylate (DDrLs)/PEI complexes [ 58 ], which is seen schematically in Fig.…”