Microencapsulation of Oil in Organically Modified Silicate Glass by Sol-Gel Process
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Microencapsulation of Oil in Organically Modified Silicate Glass by Sol-Gel Process Sang I. Seok, Bok Y. Ahn, Joo H. Kim, and Tae S. Suh Advanced Materials Division, Korea Research Institute of Chemical Technology, Taejon, 305600, KOREA ABSTRACT Microencapsulation provides protection and sustained or controlled release of active core agents. The sol-gel process has opened up a new way for encapsulating oil droplets within an inorganic capsule. Silica microcapsules were prepared in silica precursor-oil mixtures/NH4OH water microemulsion system. In this step, the formation of capsules incorporating oil depended strongly on the type of silica precursor. A spherical silica microsheres were only obtained when oligomer, synthesized by the hydrolysis and co-condensation of equiweight of TEOS (tetraethylorthosilicate) and MTMS (methyltrimethoxysilane), was used as the wall materials. The particles size of silica microcapsules was in the range of 1 ∼ 100 µm, depending on processing parameter such as a shear rate and O/W ratio etc. In controlled release system, the shell porosity is important to give an appropriate permeability, corresponding to the release rate. The pore structure, responsible for permeability, was adjusted by doping alkyl silane, and investigated with nitrogen sorption measurement. INTRODUCTION Microcapsules having oil droplets and the controlled release of content have been become increasingly important in such fields as perfume, medicine, cosmetics, and so on, due to its convenience, long-term efficacy, and safety [1,2]. Moreover, encapsulation of active agents can improve the stabilization against the environment degradation. Although interfacial polymerization between two complementary organic monomers is known as one of the simplest methods for the encapsulation of oil (water-immiscible phase) by a polymeric shell [3], the solgel technique also offers new approach for the encapsulation by an inorganic shell [4,5]. It was generally accepted that inorganic shell exhibit higher mechanical strength and negligible swelling in organic solvents compared to most organic polymers. The sol-gel process associated with a mild condition allows the encapsulation of organics within silica glasses, which has been traditionally impossible because of the very high temperatures employed in glasses. Silica glass matrix is thermally and photochemically stable without being hazardous to humans or the environment. Moreover, the physical properties of silica shell matrix can be easily modified by introducing organic groups into silica network in the form of alkyl silane. Organically modified Q6.34.1 Downloaded from https:/www.cambridge.org/core. University of Arizona, on 04 Apr 2017 at 10:27:14, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-726-Q6.34
silicate(ORMOSIL) glasses were prepared by the hydrolysis and co-condensation of appropriate inorganic and organosilicon precursors such as TEOS(tetraethylorthosilicate), MTMS (methyltrimethoxysilane),
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