Premium
Gelation and drying of weakly bonded silica‐PPO nanocomposites
Author(s) -
Chaker Juliano Alexandre,
Dahmouche Karim,
Santilli Celso Valentim,
Pulcinelli Sandra Helena,
Craievich Aldo
Publication year - 2003
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889803005089
Subject(s) - small angle x ray scattering , materials science , sol gel , nanocomposite , chemical engineering , fractal dimension , silica gel , nanoscopic scale , scattering , crystallography , chemistry , fractal , composite material , nanotechnology , mathematical analysis , physics , mathematics , engineering , optics
Silica‐poly(oxypropylene) (PPO) nanocomposites containing PPO with weak physical bonds between the organic (PPO) and inorganic (silica) phases were obtained by the sol‐gel procedure. Three precursor sols containing silica and PPO with molecular weights of 1000, 2000 and 4000g/mol were prepared. The structure changes during the whole sol‐gel process, i. e. sol formation, sol‐gel transition and gel aging and drying were investigated in situ by small angle X‐ray scattering (SAXS). The experimental SAXS curves corresponding to sols and wet gels containing PPO of molecular weight 1000g/mol indicate that the aggregates formed during the studied process are fractal objects. Close to the sol‐gel transition and during gel aging the fractal dimension is D=2.5. A clearly different structure evolution occurs in samples prepared with PPO with molecular weights 2000 and 4000 g/mol. Our SAXS results indicate the presence of two coexisting and well‐defined structure levels, one of them corresponding to small silica clusters and the other to large silica aggregates. These two levels remain along the whole transformation. The SAXS curves of all dry samples are similar to those of the corresponding wet gels suggesting that no significant changes at nanoscopic scale occur during the drying process.