Gelation of siloxane-poly(oxypropylene) composites

摘要: Abstract The viscoelastic properties of siloxane–poly(oxypropylene) (PPO) nanocomposites prepared by the sol–gel process has been analyzed during gelation dynamic rheological measurements. changes storage and loss moduli, complex viscosity phase angle measured as a function time showing newtonian sol in initial step gelation, its progressive transformation to gel. rheologic have correlated mass fractal, nearly linear growth models percolation theory. This study, completed quasi-elastic light scattering 29 Si solid state nuclear magnetic resonance measurements, shows that mechanisms siloxane–PPO hybrids depend on molecular weight polymer pH hybrid sol. For acid medium, polymerization involving silicon reactive species located at extremity chains presenting functionality f=2 occurs, forming fractal structure first stage transition. samples under neutral pH, is only observed for containing short (Mw∼130 g mol−1). dimensionality determined from change properties, indicates mechanism reaction-limited diffusion-limited aggregation when PPO increases 130 4000 g mol−1 catalyst conditions acidic neutral. Near gel point, these gels typical scaling behavior expected