Thermoreversible crosslinking of silicones using acceptor-donor interactions

Abstract

Partial charge transfer between donor and acceptor groups has been used as a tool to physically structure silicone materials. In a fi rst part, interactions between a single donor molecule, i.e. 9H-carbazole-9-ethanol, and a poly(dimethylsiloxane) functionalized on both chain-ends by acceptor groups, i.e. 3,5-dinitrobenzoate, were studied by DSC and UV-Vis analysis. The thermoreversibility of the interactions was likely demonstrated by UV-Vis analyses, which also showed a most favourable association of the complex for a 1/1 stoechiometry. The second part of this work deals with the synthesis of a triblock copolymer poly (2-(N-carbazolyl) ethyl methacrylate)-b- poly(dimethylsiloxane)-b-poly(2-(Ncarbazolyl) ethyl methacrylate) by atom transfer radical polymerization in the presence of copper bromide and 1,1,4,7,10,10-hexamethyltriethylene tetramine in THF. The association of this triblock copolymer with the telechelic acceptor-based poly(dimethylsiloxane) used in the model study has been checked by rheology, which showed on heating and cooling a thermoreversible elastic/viscoelastic transition. © 2008 Springer Science+Business Media B.V.