Morphology and size control of mesoporous ORMOSIL particles prepared from organosilane mixtures

Abstract

Mesoporous organically modified silica (ORMOSIL) particles, having various morphologies such as raspberry-shaped, hollow, rattle-type, as well as solid sphere structures, were synthesized through selective etching of organosiloxane groups in ORMOSIL particles prepared using a simple two-step process. The first step, synthesis of monodisperse ORMOSIL particles, utilized a one-pot process in an aqueous solution of a mixture comprised of various combinations of organosilane monomers: 3-aminopropyltrimethoxysilane (APTMS), vinyltrimethoxysilane (VTMS), 3-mercaptopropyltrimethoxysilane (MPTMS), methyltrimethoxysilane (MTMS), and phenyltrimethoxysilane (PTMS). In the second step, the ORMOSIL particles were treated with a mixture of water and alcohol with mild heating. This process was employed to selectively etch some of the organosiloxane groups within the ORMOSIL particles but not their main silica frameworks, leading to formation of mesoporous particles. Surface roughness, shell thickness, and size of the resultant particles were controlled by manipulating synthetic parameters such as the type and relative concentration of silane monomers. Compared to the previously developed synthetic methods, our method offers a simple, economical, and environmentally friendly way to produce complicated mesoporous ORMOSIL particles that can provide several novel properties favorable for practical applications.