pH-Sensitive C-ON Bond Homolysis of Alkoxyamines of Imidazoline Series with Multiple Ionizable Groups As an Approach for Control of Nitroxide Mediated Polymerization

pH-Sensitive C-ON Bond Homolysis of Alkoxyamines of Imidazoline Series with Multiple Ionizable Groups As an Approach for Control of Nitroxide Mediated Polymerization Full article

Journal

Journal of Organic Chemistry
ISSN: 0022-3263

Output data

Year: 2011, Volume: 76, Number: 14, Pages: 5558-5573 Pages count : DOI: 10.1021/jo200341m

Authors

Edeleva Mariya V. ^1,2 , Kirilyuk Igor A. ³ , Zhurko Irina F. ³ , Parkhomenko Dmitry A. ^1,2 , Tsentalovich Yuri P. ¹ , Bagryanskaya Elena G. ¹

Affiliations

1	(Данные Web of science) Int Tomog Ctr SB RAS, Novosibirsk 630090, Russia
2	(Данные Web of science) Novosibirsk State Univ, Novosibirsk 630090, Russia
3	(Данные Web of science) Novosibirsk Inst Organ Chem SB RAS, Novosibirsk 630090, Russia

Recently, a new concept of pH-switchable agents for reversible addition-fragmentation chain transfer (RAFT) polymerization has been introduced by Benaglia et al. (J. Am. Chem. Soc. 2009, 131, 6914-6915). In this paper we extended the concept of pH-switchable mediators to nitroxide mediated polymerization (NMP) by employing nitroxides with basic or acidic groups as controlling agents. Four alkoxyamines, the derivatives of 2-(4-(dimethylamino)-2-ethyl-5,5-dimethyl-2-(pyridin-4-yl)-2,5-dihydro-1H-imidazol-1-oxyl and 2-(2-carboxyethyl)-5,5-diethyl-2,4-dimethyl-2,5-dihydro-1H-imidazol-1-oxyl, have been prepared. The influence of pH on alkoxyamine homolysis rate constants (k(d)) and on the nitroxide-alkyl radical recombination rate constants (k(c)) was studied. All alkoxyamines under study as well as the parent nitroxides have several basic groups, which under pH variation can undergo consecutive protonation. It was shown that the kd value under basic conditions are significantly (up to 15-fold) higher than in acidic solution at the same temperature, whereas the kg value in basic solutions decrease by a factor of 2 only. The efficiency of NMP is known to be dependent on k(d) and k(c), both constants being dependent on the monomer structure; therefore the performance of NMP of different monomers in the controlled mode requires different conditions. It is shown that the pH value crucially affects the polymerization regime, changing it from the controlled to the uncontrolled mode. The controlled regime of NMP of different hydrophilic monomers (sodium 4-styrenesulphonate and acrylamide) in aqueous solution under mild conditions (90 degrees C) can be achieved using the same alkoxyamine by the variation of the pH value. The chain length of polymers depends on pH value during the polymerization.

Edeleva M.V. , Kirilyuk I.A. , Zhurko I.F. , Parkhomenko D.A. , Tsentalovich Y.P. , Bagryanskaya E.G.
pH-Sensitive C-ON Bond Homolysis of Alkoxyamines of Imidazoline Series with Multiple Ionizable Groups As an Approach for Control of Nitroxide Mediated Polymerization
Journal of Organic Chemistry. 2011. V.76. N14. P.5558-5573. DOI: 10.1021/jo200341m WOS Scopus РИНЦ

Published print:

Jul 15, 2011

Web of science	WOS:000292480300006
Scopus	2-s2.0-79960156763
Elibrary	17004194
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