Thiols as chain transfer agents in free radical polymerization in aqueous solution

Henriquez, C; Bueno, C; Lissi, EA; Encinas, MV

Abstract

The behavior of thiophenol and aliphatic thiols of different structure as chain transfer agents in the polymerization of acrylamide and 1-vinyl-2-pyrrolidone in aqueous solution at 25°C was studied. Addition of millimolar concentrations of thiols to acrylamide polymerization reduced notably the polymer molecular weights, without change of the polymerization rate. Measurements at different pH showed that the reactive species towards the macroradicals is the protonated -SH group. Chain transfer constants, determined from Mayo plots, are only slightly dependent on the thiol structure. Aliphatic thiols and thiophenol react at similar rates. The selectivity is opposite for acrylamide (electron acceptor) and 1-vinyl-2-pyrrolidone (electron donor), pointing to significant charge transfer contributions. The reactions rates of these sulfur compounds with the electrophilic DPPH radical showed higher selectivity, and are not related with the chain transfer constants measured for the acrylamide macroradicals. These results are explained in terms of the different factors that control the reactivity of thiols with macroradicals. © 2003 Elsevier Ltd. All rights reserved.

Más información

Título según WOS: Thiols as chain transfer agents in free radical polymerization in aqueous solution
Título según SCOPUS: Thiols as chain transfer agents in free radical polymerization in aqueous solution
Título de la Revista: POLYMER
Volumen: 44
Número: 19
Editorial: Elsevier
Fecha de publicación: 2003
Página de inicio: 5559
Página final: 5561
Idioma: English
URL: http://linkinghub.elsevier.com/retrieve/pii/S0032386103005810
DOI:

10.1016/S0032-3861(03)00581-0

Notas: ISI, SCOPUS