Research On Preparation Of Polymer Microparticles By Solventing-out Crystallization

Solventing-out crystallization is based on the remarkable difference of target component's solubility in the main solvent and anti-solvent. It is an important separation and purification technique, which is widely used in the areas of chemical industry, pharmaceutical and food industry. However there are few researches on preparation of polymer particles by solventing-out crystallization. Solventing-out crystallization is applied to prepare polystyrene (PS) and poly-methyl-methacrylate (PMMA) particles in this study.Solventing-out crystallization was applied to prepare the polystyrene (PS) microparticles using ethanol as anti-solvent and chloroform as main solvent. The solubility of PS in ethanol, chloroform and ethanol + chloroform mixtures was measured firstly. The PS microparticles prepared were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), laser diffraction-based particle size analyzer and UV-visible spectrophotometer. The analysis results show that PS microparticles obtained are spherical particles with mean sizes of 150 ~ 600 nm. The effects of feed rate, feed concentration, agitation intensity and crystallization temperature in the solventing-out crystallization were also investigated. The experiment results indicate that proper feed concentration, higher feed rate, lower crystallization temperature and faster agitation will lead to precipitation of smaller PS microparticles.Solventing-out crystallization was also applied to prepare the poly-methyl-methacrylate (PMMA) microparticles. Different systems of main solvent/ anti-solvent were selected to prepare PMMA microparticles. It was found that different systems of main solvent/ anti-solvent have a great effect on the morphology and size of polymer microparticles.