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Which Side-Reactions Compromise Nitroxide Mediated Polymerization?

Abstract (Expand)

The mechanism of the nitroxide mediated polymerization (NMP) is well understood, however less is known about the side-reactions that interfere and in certain cases severely compromise it. Experimental … studies inevitably involve model fitting leading to at times contradictory conclusions as to which elementary side-reactions are behind the failure of a given NMP system. In the present work we use high-level quantum-chemical calculations to obtain the rate coefficients of the various side-reactions, both suggested previously and considered here for the first time, and first principles PREDICI kinetic simulations to identify the most deleterious side-reactions involved in the TEMPO, SG1 and DPAIO mediated polymerization of styrene, acrylate and methacrylate monomers. We show that the core mechanism for the thermal decomposition of alkoxyamines differs between the uni- and polymeric species, which often makes such experiments not suitable for modelling the NMP conditions. We also find that the main side-reaction responsible for the failure of TEMPO and SG1 in methacrylate homopolymerization is an intramolecular alkoxyamine decomposition (often referred to as ‘disproportionation’) via a Cope-type elimination, however in the case of SG1 the polymerization outcome is additionally affected by the equilibrium constant of alkoxyamine bond homolysis. On the basis of these findings, complemented by a thorough analysis of available experimental data, we define guidelines for minimising occurrence of the side-reactions and thus improving NMP. Finally, the accurate first principles rate parameters reported in this study should prove useful for subsequent kinetic modelling oriented at optimising different polymerization conditions.

Authors: Ganna Gryn'ova, Ching Yeh Lin, Michelle L. Coote

Date Published: 2013

Publication Type: Journal

Computational Evaluation of the Sulfonyl Radical as a Universal Leaving Group for RAFT Polymerisation

Abstract (Expand)

The present study investigates the performance of the sulfonyl radical, i.e. •SO2Ph, as a universal leaving group in reversible addition–fragmentation chain-transfer (RAFT) polymerisation. The sulfonyl … radical is widely used as a radical initiator and has already been proved successful as a leaving group in an atom-transfer radical polymerisation. Our results, obtained using high-level ab initio computational methodology under relevant experimental conditions, indicate superior performance of the sulfonyl compared with a reference cyanoisopropyl group in controlling RAFT of a wide range of monomers. Importantly, the presence of sulfonyl chain ends in the polymers so formed opens attractive possibilities for further functionalisation. Potential synthetic routes to the R-sulfonyl RAFT agents are discussed.

Authors: Ganna Gryn'ova, Tamaz Guliashvili, Krzysztof Matyjaszewski, Michelle L. Coote

Date Published: 2013

Publication Type: Journal

Conformational diversity and ligand tunnels of mammalian cytochrome P450s

Abstract

Not specified

Authors: Xiaofeng Yu, Vlad Cojocaru, Rebecca C. Wade

Date Published: 2013

Publication Type: Journal

Treating Conformational Flexibility in Protein-Protein Docking

Abstract

Not specified

Authors: Mykhaylo Berynskyy, Rebecca C. Wade

Date Published: 2013

Publication Type: Journal

An Algorithmic Approach to Peptidomimetics

Abstract

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Author: Priyanka Banerjee

Date Published: 2013

Publication Type: Master's Thesis

Uso di inhibitori della Pteridina Reduttasi per la prevenzione e/o il trattamento di infezioni parassitarie

Abstract

Not specified

Authors: M. Paola Costi, Rosaria Luciani, Erika Nerini, Guerrieri D., Stefania Ferrari, Alberto Venturelli, Sandra Lazzari, Rebecca C. Wade, Stefan Henrich, D. Motiejunas

Date Published: 2013

Publication Type: Misc

Uncertainty quantification in complex simulation models using ensemble copula coupling

Abstract

Not specified

Authors: Roman Schefzik, Thordis L. Thorarinsdottir, Tilmann Gneiting

Date Published: 2013

Publication Type: Journal

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