SAXS studies of silica/vinyl polymer nanocomposite films.

P.J. PERUZZO; J.I. AMALVY

Activity Report/Brazilian Syncrhrotron Light Laboratory

Lugar: Campinas, Brasil.; Año: 2006 vol. 2005 p. 1 - 2

1518-0204

In polymer nanocomposites the polymer chains are confined to nanoscale dimensions (1-10 nm). These materials have unusual properties which cannot be obtained simply by co-mixing the polymeric component with the inorganic phase at the macroscopic level. Film-forming, silica-based materials are useful as tough, abrasion-resistant coatings. In this work, films of vinyl polymer/silica nanocomposite particles were studied by SAXS. Samples were prepared by polymerization of 4-vinylpyridine, n-butyl acrylate and monomethoxy-capped poly(ethylene glycol) methacrylate (MPEGMA 2K) in the presence of 20 nm silica sol (Nyacol 2040, Akzo Nobel). Films were prepared by casting the aqueous dispersions and evaporating the water at room temperature. A monochromatic beam of wavelength 1.488 A was used and the scattering intensity was registered using a sample-detector distance of 1084.3 mm. The SAXS spectra of samples show features at low q, which are more clearly seen as sharp peaks in the Kratky plot (Iq2 vs q). These features are due to the high difference electron density between the silica and the polymer components. Scattering intensity increases as silica content of sample increases from 40 to 56 wt%. Features observed at q values around 0.026 ºA-1 correspond to a correlation lenght of 23-25 nm, very close to the nominal diameter of silica particles. Additional broad peaks of lower intensity are also observed at 0.25 ºA-1 corresponding to a correlation distance of 2 nm, probably related to the electron density contrast at the particle/polymer matrix interface.