Evolution of rheological properties and local structure during gelation of siloxane-polymethylmethacrylate hybrid materials
Nenhuma Miniatura disponível
Data
2006-03-01
Autores
Sarmento, VHV
Frigerio, M. R.
Dahmouche, K.
Pulcinelli, Sandra Helena [UNESP]
Santilli, Celso Valentim [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Springer
Resumo
Hybrid siloxane-polymethylmethacrylate (PMMA) nanocomposites with covalent bonds between the inorganic (siloxane) and organic (polymer) phases were prepared by the sot gel process through hydrolysis and polycondensation of 3-(trimethoxysilyl)propylmethacrylate (TMSM) and polymerization of methylmethacrylate (MMA) using benzoyl peroxide (BPO) as initiator. The effect of MMA, BPO and water contents on the viscoelastic behaviour of these materials was analysed during gelation by dynamic rheological measurements. The changes in storage (G') and loss moduli (G), complex viscosity (eta*) and phase angle (6) were measured as a function of the reaction time showing the viscous character of the sot in the initial step of gelation and its progressive transformation to an elastic gel. This study was complemented by Si-29 and C-13 solid-state nuclear magnetic resonance (NMR/MAS) measurements of dried gel. The analysis of the experimental results shows that linear chains are formed in the initial step of the gelation followed by a growth of branched structures and formation of a three-dimensional network. Near the gel point this hybrid material demonstrates the typical scaling behaviour expected from percolation theory.
Descrição
Palavras-chave
hybrids, sol-gel transition, rheology
Como citar
Journal of Sol-gel Science and Technology. Dordrecht: Springer, v. 37, n. 3, p. 179-184, 2006.