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

*Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.


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).


Sol Gel process

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.





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