Determination of Activation and Deactivation Rate Constants of Model Compounds in Atom Transfer Radical Polymerization

Abstract

The activation and deactivation rate constants in atom transfer radical polymerization (ATRP) were measured using model compounds. The activation rate constants were determined using HPLC or GC under the kinetic isolation condition achieved by trapping the generated radical with 2,2,6,6tetramethylpiperidinyl-1-oxy (TEMPO). The deactivation rate constants were measured by trapping 1-phenylethyl radicals with TEMPO in a competitive reaction. The effects of several parameters in ATRP systems were examined, including alkyl groups, ligands, transferred groups, and solvents. The data obtained were consistent with ATRP kinetics and provided further quantitative insights into understanding the ATRP processes.

Simulation of temperature effect on the structure control of polystyrene obtained by atom-transfer radical polymerization

“…860×10 9 exp(-2245/T) Matyjaszewski [28] k t0 3. 820×10 9 exp(-958/T) Fu et al [25] k t k t0 ×exp(-2×(A 1 X + A 2 X [2] + A 3 X [3] )) Hui and Hamielec [29] k tc 0.99k t Fu et al [25] k td 0.01k t Fu et al [25] k t,p 10…”

Atom transfer radical polymerization in aqueous dispersed media

“…Selection of a suitable catalyst enables the system to establish a dynamic equilibrium between propagating chains and dormant chains, as well as to assure fast initiation, reduction of the contribution of the inevitable radicalradical termination reactions which ultimately results in the controlled/"living" character of the polymerization [28]. In an ATRP, the catalyst is usually a transition metal complex, in which the ligand plays a critical role in determining the reactivity of the catalyst complex [10,[29][30][31][32][33][34]. In addition, the ligand also strongly influences the solubility of the complex, and consequently the concentration of activators and deactivators in the reaction medium [18,[35][36][37][38][39][40].…”

Understanding the mechanisms of transition metal catalysed redox reactions

“…This may explain why in various polymer syntheses, the deactivation reaction is slower with chloride than bromide. 40,59 As a whole, the data indicate that the deactivation reaction to produce R-X, and [Cu I (L)] + species will be more favoured for X = Br -than when X = Cl -.…”

“…20,[35][36][37] However, this effect has mostly been rationalised in terms of changes to the activation rate (kact). [38][39][40][41][42][43][44][45][46][47][48] A second, experimental method has also been applied in a limited number cases using a competitive clock reaction. 40 Here a radical R…”

“…Whilst the relationship between kdeact and the solvent is not well understood, two papers suggest that deactivation is slower in more polar solvents. 40,48 Various empirical parameters have been developed in order to rank solvents according to their polarity. [107][108][109][110][111] One of the most successful of these is the normalised Dimroth-Reichardt parameter 'E N T ' which varies between 1.000 (water) and 0.000 (tetramethylsilane) for the extremes of polar and nonpolar solvents respectively.…”