Evaluation of Silica Sol-Gel Microcapsule for the Controlled Release of Insect Repellent, N,N-Diethyl-2-methoxybenzamide, on Cotton
Ann Shireen Chan, Judy del Valle, Kendricks Lao,
Christian Malapit, Modesto Chua, and Regina C. So*
Department of Chemistry, Ateneo de Manila University,
School of Science and Engineering, Loyola Heights, Quezon City 1108
N,N-diethyl-2-methoxybenzamide, an insect repellent compound, was incorporated into cotton textile using the sol-gel method. Evaluation of the results of four different sol-gel formulations showed that a lower condensation rate resulted in significantly better encapsulation. Also investigated was the encapsulation in the presence of other polymers like polymethylmethacrylate (PMMA), polystyrene (PS) and polyvinyl alcohol (PVA) that prolong the release of the repellent. The sol-gel formulation, SiO2: polymethylmethacrylate (PMMA) (1:0.8), gave smooth fabric and good encapsulation of the insect repellent compound. PS and PVA resulted in cloths which are aesthetically undesirable. Cloths coated with sol-gel PVA gave the best repellent release profile.
The sol-gel process is a versatile solution technique for encapsulating and depositing functional compounds on different materials (Penard et al. 2007; Trewyn et al. 2007). The process typically involves the hydrolysis of inorganic metal salts or metal-organic compounds such as metal alkoxides, forming a colloidal suspension or sol. The sol subsequently polymerizes forming a wet gel. Heat is applied to remove the solvent, yielding a ceramic material (Figure 1) (Veith et al. 2005).
Fig1. Sol-gel process in the presence of insect repellent compound: The inorganic salt is hydrolyzed to form a sol. The repellent compound is added to the sol, and the cloth is coated by dip method. Heat is applied to the coated material to anneal.
Recent research has shown that the sol-gel method can be used to fabricate a variety of new materials such as thin-film coatings (Tshabalala et al. 2003), ceramic-coated fibers (Zhou et al. 1997), microporous inorganic membranes (de Lange et al. 1995), monolithic ceramics and glasses (Siouffi 2003), and extremely porous aerogel materials (Hench and West 1990). This method can be used to create sol-gel thin films for the encapsulation of insect repellents on cloth.
BARLETT KN, KOLAKOWSKI RV, KATUKOJVALA S, WILLIAMS LJ. 2006. Thio Acid/AzideAmidation: An Improved Route to N-Acyl Sulfonamides. Org Lett 8: 823-826.
BÖTTCHER H, KALLIES KH, HAUFE H, SEIDEL J. 1999. Silica Sol-Gel Glasses with Embedded Organic Liquids. Adv Mater 11: 138-141.
DE LANGE RSA, KEIZER K, BURGGRAAF AJ 1995. Analysis and theory of gas transport in microporous sol-gel derived ceramic membranes. J Membr Sci 104: 81-100.
HENCH LL, WEST JK. 1990. The sol-gel process. Chem Rev 90: 33-72.
MAHLTIG B, HAUFE H, BÖTTCHER H. 2005. Functionalisation of textiles by inorganic sol–gel coatings. J Mater Chem 15: 4385.
NEISES B, STEGLICH W. 1990. Esterification of Carboxylic acids with dicyclohexylcarbodiimide/4- dimethylaminopyridine: tert-butyl ethyl fumarate. Org Synth 63: 183-185.
OLSHER U, SHOHAM G, DALLEY NK, WEINING J, LUBOCH E, YU ZY, KNOBELOCH J M, LEE JC, TALANOV VS, RICHARD AB. 1999. Structural and conformational studies of alcohol, diol and methylether derivatives of dibenzo-14-crown-4. Implications for ligand and tecton design. J Chem Soc Perkin Trans 2(2): 2557-64.
PENARD AL, GACOIN T, BOILOT, JP. 2007. Functionalized Sol–Gel Coatings for Optical Applications. Acc Chem Res 40: 895-902.
QUELLET C, SCHUDEL M, RIGGENBERG R. 2001. Flavors and Fragrance Delivery Systems. Chimia 55: 421-428.
SIOUFFI AM. 2003. Silica gel-based monoliths prepared by the sol–gel method: facts and figures. J Chromatogr A 1000: 801-818.
TREWYN BG, SLOWING II, GIRI S, CHEN HT, LIN VSY. 2007. Synthesis and Functionalization of a Mesoporous Silica Nanoparticle Based on the Sol-Gel Process and Applications in Controlled Release. Acc Chem Res 40: 846-853.
TSHABALALA MA , KINGSHOTT P, VANLINDINGHAM MR, PLACKETT D. 2003. Surface Chemistry and Moisture Sorption Properties of Wood Coated with Multifunctional Alkoxysilanes by Sol-Gel Process. J Appl Polym Sci 88: 2828-41.
VEITH SR, PERREN MJ, PRATSINIS SE. 2005. Encapsulation and retention of decanoic acid in sol-gel made silicas. J Colloid Interface Sci 283: 495-502.
VEITH SR, PRATSINIS SE, PERREN MJ. 2004. Aroma Retention in Sol-Gel-Made Silica Particles. J Agric Food Chem 52: 5964-71.
ZHOU QF, CHAN HLW, CHOY CL. 1997. Nanocrystalline powder and fibres of lead zirconate titanate prepared by the sol-gel process. J Mater Process Technol 63: 281-285.