(264c) Formation of Porous Aluminosilicate Microspheres Via Nanoparticle Assembly

We recently developed a polymer-mediated assembly approach to solid and hollow spheres [1-4]. In the polymer-aggregating templating route, a solution of a cationic polymer like poly(allylamine hydrochloride) is combined with an anionic salt solution, to form a suspension of salt-bridged polymer aggregates. An aqueous suspension of nanoparticles (NPs), such as silica NPs, is then added to form polymer-filled capsules, water-filled capsules, and polymer/inorganic solid spheres, depending on the synthesis conditions. This electrostatically-driven synthesis route is attractive for microcapsule scale-up because the formation reaction occurs in water at mild pH values and at room temperature. The objective of study is gain deeper understanding of NP assembly chemistry by replacing negatively-charged silica NPs with positively-charged NPs (Ludox brand, alumina-doped silica NPs). Somewhat surprisingly, we were able to generate aluminosilicate/polymer solid spheres. We studied the effect of synthesis parameters like NP concentration, final solution pH, and polymer-salt aggregate aging time. We will discuss the formation mechanism of these spheres and their resultant mesoporous properties after calcination at 600 °C. These results indicate that the polymer-aggregate templating mechanism underlying NP assembly chemistry can be modified to yield mesoporous aluminosilicates of controlled porosity and particle size.

References: [1] R. K. Rana, V. S. Murthy, J. Yu, and M. S. Wong, Adv. Mater. 17, 1145-1150 (2005) [2] V. S. Murthy, R. K. Rana, and M. S. Wong, J. Phys. Chem. B., 110 (51), 25619 -25627 (2006) [3] J. Yu, V. S. Murthy, R. K. Rana, and M. S. Wong, Chem. Commun. 10, 1097-1099 (2006) [4] J. Yu, M. A. Yaseen, B. Anvari, and M. S. Wong, Chem. Mater. 19(6), 1277 ? 1284(2007)