Characterization of physical structure of silica nanoparticles encapsulated in polymeric structure of polyamide films.

Polyamide nanocomposite films were prepared from nanometer sized silica particles and trimesoyl chloride-m-phenylene diamine based polyamides. The type of silica nanoparticles used is commercial LUDOX HS-40 and the particle size characterized by the radius of gyration (R(g)) is about 66 A. The immediately prepared films were easily broken into particles to form colloidal-like dilute suspension of the silica-polyamide composite particles in D(2)O-H(2)O solutions for SANS measurements, that in this dilute system SANS data the complication of scattering data from the interacting particles is minimized. At about 60% D(2)O of the sample solution, the silica is contrasted out, therefore the SANS profiles are predominantly from the organic polyamide scattering. The SANS profile of the sample solutions measured at 90% D(2)O clearly indicates scattering from both silica and polymer. The scattering heterogeneities for two-phase system were evident from the validity of the Debye-Bueche expression in case of the nanocomposite with high silica loading. At limited silica loading of the nanocomposite, interaction between the silica and polymer chains forming core-shell morphology was observed. The transport properties of the membranes made from the nanocomposite films were measured on a batch type test kit with an aqueous solution of 500 ppm dioxane concentration at pressures ranging from 50 to 200 psig, and correlated to their composite structure.