Preparation of Electrosprayed Poly(caprolactone) Microparticles Based on Green Solvents and Related Investigations on the Effects of Solution Properties as Well as Operating Parameters

Electrosprayed poly(caprolactone) (PCL) microparticles were produced using five solvents (ethyl acetate, acetone, anisole, glacial acetic acid and chloroform) under different PCL concentrations and operating parameters. Not only green and appropriate solvent for PCL electrospraying was pointed out, but also the effects of solution properties (surface tension, electrical conductivity, viscosity and vapor pressure) and operating parameters (flow rate, working distance and applied voltage) on the formation of electrosprayed particles were clarified. The formation and shape of Taylor cone during electrospraying was observed by high-speed images captured with a camera, and the size and morphology of electrosprayed particles were characterized by optical and scanning electron microscopies. It can conclude that the cone–jet range of applied voltage mainly depended on electrical conductivity, and an ideal Taylor cone was easier to form under high viscosity and low surface tension. Although high electrical conductivity was a contributor to fabricate tiny particles, it was easier to fabricate mono-dispersed microparticles under low electrical conductivity. The poly-dispersed distribution obtained with a high electrical conductivity converted into mono-dispersed distribution with the increasing of viscosity. Furthermore, the size of electrosprayed particles also correlated with the surface tension and vapor pressure of the solvent used. Ethyl acetate, due to mild electrical conductivity and surface tension, moderate viscosity and vapor pressure, is a green and suitable solvent for PCL electrospraying. Single pore PCL microparticles with smooth cherry-like morphology can be prepared from ethyl acetate. Finally, long working distance not only stabilizes the break-up of charged jet, but also promotes the evaporation of solvent.