Structure and Growth Kinetics of 3-Glycidoxypropyltrimethoxysilane-Derived Organic/Silica Hybrids at Different Temperatures

Abstract

The structure and the growth kinetics of 3-glycidoxypropyltrimethoxysilane(GPTS)-derived organic/silica hybrids have been studied in situ by small-angle X-ray scattering (SAXS) at 298, 316, and 334 K. The SAXS data were compatible with the growth of silica-rich domains from a fixed number of primary particles, with polydispersity likely increasing with time. The isothermal growth of the average radius of gyration Rg of the domains occurs in a power law with time t as Rg ∝ (t – t0)α, with t0 being a small offset time and α = 0.247 in the studied temperature range. The SAXS intensity I(0) extrapolated to q = 0 increases in a power law with time as I(0) = B(t – t0)β, where B is a function of temperature and β a constant equal to 0.443 in the studied temperature range. The activation energy was evaluated as ΔE = 67.7 ± 1.1 kJ/mol from an Arrhenius equation for the rate constant k = βB1/β. The extrapolated intensity I(0) scales with Rg as I(0) ∝ RgD with D = 1.71 ± 0.01 in the studied temperature range, in good agreement with the value β/α = 1.79 ± 0.07 from the kinetic study. This suggests that the macromolecules grow in a dimensionality ∼1.7, typical of macromolecules in good solvent conditions in diluted or semidiluted solution. A time-independent function F(qRg) = I(q,t)Rg–D/Q, where Q is the invariant, was found to hold for every time and temperature within a domain limited by a primary particle size. This finding suggests that the system exhibits primary-particle-size-limited dynamic scaling properties.