Time-Resolved Small-Angle X-ray Scattering Studies of Polymer−Silica Nanocomposite Particles: Initial Formation and Subsequent Silica Redistribution

• Published in: Journal of the American Chemical Society 2011-02, Vol.133 (4), p.826-837
• Main Authors: Balmer, Jennifer A, Mykhaylyk, Oleksandr O, Armes, Steven P, Fairclough, J. Patrick A, Ryan, Anthony J, Gummel, Jeremie, Murray, Martin W, Murray, Kenneth A, Williams, Neal S. J
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja106924t

Small angle X-ray scattering (SAXS) is a powerful characterization technique for the analysis of polymer−silica nanocomposite particles due to their relatively narrow particle size distributions and high electron density contrast between the polymer core and the silica shell. Time-resolved SAXS is used to follow the kinetics of both nanocomposite particle formation (via silica nanoparticle adsorption onto sterically stabilized poly(2-vinylpyridine) (P2VP) latex in dilute aqueous solution) and also the spontaneous redistribution of silica that occurs when such P2VP−silica nanocomposite particles are challenged by the addition of sterically stabilized P2VP latex. Silica adsorption is complete within a few seconds at 20 °C and the rate of adsorption strongly dependent on the extent of silica surface coverage. Similar very short time scales for silica redistribution are consistent with facile silica exchange occurring as a result of rapid interparticle collisions due to Brownian motion; this interpretation is consistent with a zeroth-order Smoluchowski-type calculation.