Preparation and characterization of single- and double-shelled cyhalothrin microcapsules based on the copolymer matrix of silica–N-isopropyl acrylamide–bis-acrylamide

Silica, as a controlled release material, has been applied widely in many fields owing to its high thermal and mechanical stability, corrosion resistance, biocompatibility and low cost. We herein synthesized pesticide cyhalothrin/SiO2 microcapsules and cyhalothrin/silica–N-isopropyl acrylamide (NIPAM)–bis-acrylamide (MBA) microcapsules. A silica shell was formed through the hydrolysis and polycondensation of tetraethyl orthosilicate under alkaline conditions, and then the single-shelled silica microcapsules were modified by triethoxyvinylsilane and cross-linked with NIPAM and MBA through free radical polymerization. The microcapsules were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis, and their release kinetics and biological activity were also detected. The single- and double-shelled microcapsules had excellent loading abilities for cyhalothrin (about 50.0% and 25.0%, respectively). The release curves showed that the double-shelled microcapsules allowed better controlled release, probably through a combination of diffusion and erosion. The microcapsules showed longer persistence than that of cyhalothrin emulsifiable concentrate. This study provides a novel material for fabricating pesticides with controlled release.