Temperature Effect on Activation Rate Constants in ATRP: New Mechanistic Insights into the Activation Process

Abstract

Activation rate constants (k act ) for a variety of initiators for Cu-mediated ATRP were measured with Cu(I)Br(PMDETA) at various temperatures (i.e., -40 to þ60°C). Reactions of less active alkyl halides were more accelerated by increased temperatures than reactions of more active initiators. Straight Eyring and Arrhenius plots were obtained, from which the activation parameters (i.e., ΔH q , ΔS q , E a , and ln A) were determined. The activation enthalpies ΔH q are in between 26.0 and 38.7 kJ mol -1 with highly negative activation entropies (ΔS q =-156 to -131 J mol -1 K -1 ), which indicate greatly ordered structures of the transition states for these reactions.

Computer‐Aided Optimization of Conditions for Fast and Controlled ICAR ATRP of n‐Butyl Acrylate

“…[68][69][70][71] For activation of the ATRP initiator a value of 3.1 L Á mol À1 Á s À1 is considered based on the experimental study of Seeliger and Matyjaszewski. [72] The remaining secondary and tertiary activation and deactivation intrinsic rate coefficients are adjusted according to the experimental data of Ahmad et al [32] As discussed below, the obtained values are consistent with literature values and confirm the higher stability of tertiary macrospecies. For ICAR ATRP, dissociation of the conventional radical initiator and activation, deactivation and propagation involving conventional radical initiator fragments are also considered (Table 1).…”

Synthesis of cationic star polymers by simplified electrochemically mediated ATRP

“…In contrast, less polar solvent condition such as anisole mixture would require higher concentration of the supporting electrolyte to achieve better conductivity [60]. Moreover it is well known that temperature plays a vital role in controlled polymerization systems, because the activation rate constants increased with increasing temperature [61,62]. Thus, the objective of this study was to investigate and optimize polymerization conditions for seATRP of DMAEMA (in terms of R p , controlled MWs and narrow MWDs).…”

Kinetic Modeling of ICAR ATRP

“…Literature data were used to calculate the related individual apparent rate coefficients. [32][33][34][35][36][37][38][39] The chain length dependent apparent termination rate coefficients were calculated from the parameters obtained by the reversible addition fragmentation chain transfer-chain length dependent-termination (RAFT-CLD-T) method, with corrections for the presence of solvent. [32,33,40] For S, these parameters were determined at 363 K, however, as a first approximation, these values are also expected to hold at 353 K, the temperature used in this work.…”