Predictive Tool for Design and Analysis of ARGET ATRP Grafting Reactions

Abstract

Solving a comprehensive, yet simple, reaction model for describing the activators regenerated by electron transfer (ARGET)–atom transfer radical polymerization (ATRP) reaction cascade, we show that the molar ratios of transition metal catalyst to initiator and reducing agent to catalyst are critical parameters in the ARGET ATRP mechanism, with optimal values on the order of 0.1:1 and 10:1, respectively. The model also predicts an optimal molar ratio of reducing agent to initiator of 1:1. The ARGET ATRP reaction cascade is extremely complex with many adjustable species concentrations and reaction parameters. The effect of varying any of these parameters on the resulting temporal conversion trajectory of the polymerization is not straightforward. This analysis greatly simplifies the process allowing one to select the proper conditions to optimize the reaction and could save much effort, time and money. These results have severe implications when grafting polymer chains from surfaces, since the amount of surface-bound initiator is very low relative to the amount of catalyst. This suggests adding a sacrificial initiator to the reaction solution when grafting from surfaces is necessary to prevent loss of control on the polymerization. The most viable parameter for both increasing the polymerization rate and maintaining maximum attainable conversion for the ARGET ATRP system is to increase the reaction temperature. For broad use, the model was developed in MATLAB to predict conversion versus time behavior in the ARGET ATRP reaction cascade using an inexpensive ligand. Utilizing known rate constants and pre-exponential factors to the Arrhenius equations from the literature, the model was able to predict published experimental data for the methyl methacrylate (MMA), styrene (St), and glycidyl methacrylate (GMA) monomers at various temperatures. The main assumptions of the model are that termination reactions occur through radical coupling only and the propagation and termination reaction rates are chain length independent. The resulting model is shown to be very accurate, especially at conversions of 0.4 and lower. Sensitivity analyses were performed on the ARGET ATRP mechanism using MMA as a model monomer to identify key reaction parameters to ensure successful controlled polymerization.

Control of Dispersity and Grafting Density of Particle Brushes by Variation of ATRP Catalyst Concentration

“…The apparent rate constant of polymerization, k p app , was calculated by eq S2, and a trend between the rate and the initial catalyst concentration is shown in Figure S1, the literature values of propagation rate constant k p,MMA = 833 M –1 s –1 at 60 °C was used to calculate the radical concentration, Figure S2. , The polymerization rate of a classic ARGET ATRP reaction is defined by the ratio of the rates of reduction of Cu II /L to Cu I /L and radical termination. Thus, the overall rate should obey 1/2 order in both [RA] and [Cu II /L]. , Figure S1 shows PMMA particle brushes polymerization rate indeed follows the ARGET kinetics and the reaction order in Cu II /L has a slope of 0.47. The initial concentration of the catalyst also significantly affected the dispersity (control) of polymers formed in the reactions.…”

“…Thus, the overall rate should obey 1/2 order in both [RA] and [Cu II /L]. 41,45 Figure S1 shows PMMA particle brushes polymerization rate indeed follows the ARGET kinetics and the reaction order in Cu II /L has a slope of 0.47. The initial concentration of the catalyst also significantly affected the dispersity (control) of polymers formed in the reactions.…”

Membrane Filtration with Liquids: A Global Approach with Prior Successes, New Developments and Unresolved Challenges

“…[39] By controlling the density,b ranch length and height (using activators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP)) of the brushes,i n addition to their cross-linking intensity and type of MOFs, stiff well-defined pore size distribution membranes are expected. [40] Thus,e lucidating the fundamental principles underlying as tructure-by-design synthetic hybrid metalorganic brush (MOB) polymer membranes combining tunable polymer brush layers with complexed metals is needed. These hybrid MOB layers represent an ew class of synthetic…”

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

“…Modeling approaches applied to ATRP can broadly be categorized into deterministic − and stochastic − approaches. The most popular deterministic methods are the reaction rate equations and the method of moments .…”

“…Modeling approaches applied to ATRP can broadly be categorized into deterministic − and stochastic − approaches. The most popular deterministic methods are the reaction rate equations and the method of moments . The reaction rate equations offer the coarsest models and are unable to provide information regarding individual polymer chains, molecular weight distribution, number- and weight-average molecular weights, and polydispersity index.…”