Interaction of poly(ethylene glycol) with fumed silica and alumina/silica/titania

The characteristics of composites with PEG (35 kDa) – nanooxides (fumed silica A-300, SBET = 342 m2/g, and alumina/silica/titania (AST) at oxides content of 22, 28, and 50 wt%, respectively, SBET = 38 m2/g) were studied depending on PEG content (CPEG = 100, 90, 80, 40, and 20 wt%) at different temperatures and various hydration using Fourier transform infrared (FTIR) spectroscopy, photon correlation spectroscopy (PCS), differential scanning calorimetry (DSC), thermally stimulated depolarization current (TSDC), and dielectric relaxation spectroscopy (DRS) methods. In the aqueous suspensions the secondary particle (aggregates of primary particles) size distribution corresponds to larger particles for PEG/AST than PEG/A-300. For composite powders (0.3–3 wt% of water) with well distributed macromolecules (according to the FTIR spectra) the relaxation characteristics (temperature of relaxation maxima, activation energy of relaxation, glass transition temperature and activation energy) show that overall interaction is stronger for PEG/A-300 but local interaction in the adsorption layer is stronger for PEG/AST because of much greater SBET of A-300 (first effect) and stronger Brønsted acid sites in AST (second effect).