SANS study to probe nanoparticle dispersion in nanocomposite membranes of aromatic polyamide and functionalized silica nanoparticles

Silica nanoparticles produced from organically functionalized silicon alkoxide precursors were incorporated into polyamide film to produce a silica–polyamide nanocomposite membrane with enhanced properties. The dispersion of the silica nanoparticles in the nanocomposite membrane was characterized by performing small-angle neutron scattering (SANS) measurements on dilute reactant systems and dilute solution suspensions of the final product. Clear scattering of monodisperse spherical particles of 10–18 Å Rg were observed from dilute solutions of the initial reactant system. These silica nanoparticles initially reacted with diamine monomers of polyamide and subsequently were transformed into polyamide-coated silica nanoparticles; finally nanoparticle aggregates of 27–45 Å Rg were formed. The nanoparticle dispersion of the membrane as the nanosized aggregates is in corroboration with ring- or chain-like assemblies of the nanoparticles dispersed in the bulk polyamide phase as observed by transmission electron microscopy. It is demonstrated that dispersions of silica nanoparticles as the nanosized aggregates in the polyamide phase could be achieved in the nanocomposite membrane with a silica content up to about 2 wt.%. Nanocomposite membranes with higher silica loading ∼10 wt.% lead to the formation of large aggregates of sizes over 100 Å Rg in addition to the nanosized aggregates.

Graphical abstractNanocomposite membrane of polyamide and functionalized silica nanoparticles with particle dispersion as nanoscale aggregates was characterized using SANS.Figure optionsDownload full-size imageDownload high-quality image (58 K)Download as PowerPoint slideResearch highlights► Advantages of nanocomposite membranes of polyamide and functionalized silica nanoparticles. ► Characterization of the nanoparticle dispersion in polymer is important. ► SANS study to probe dispersion of the silica nanoparticles. ► Nansoscale aggregation evident even at low silica loading. ► SANS results corroborate with TEM observation.