Preparation and evaluation of organosilica nanocapsules encapsulating DCOIT by using the response surface optimization

Antifouling agent 4, 5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in a one-stage process based on the self-catalytic reaction between methyl trimethoxysilane (MTMS) and 3-aminopropyl trimethoxysilane (APS) in an aqueous system without any surfactants and catalysts have been developed. The optimal preparation process parameters of organosilica nanocapsules encapsulating DCOIT (DCOIT@SiNC) were determined using response surface methodology (RSM) based on the single-factor experimental results. The results of RSM optimization showed that 49.51% encapsulation efficiency (EE [%]) would be achieved with a shell-core mass ratio of 5.59:1, a MTMS-APS mole ratio of 1.52:1, and a reaction temperature of 31 degrees C. DCOIT@SiNC prepared according to the RSM optimal process exhibited a decent uniform sphericity with an average particle diameter of 660.50 nm. The encapsulation was characterized by Fourier-transform infrared and X-ray diffraction. The loading efficiency and thermal stability were verified via thermogravimetric analysis. Compared to DCOIT, DCOIT@SiNC had better controlled release performance, and the release kinetics investigated by Riger-peppas model indicated that the release of DCOIT was diffusion-controlled.