Preparation of aromatic polycarbonate nanoparticles using supercritical carbon dioxide

摘要

A novel synthetic process for producing aromatic polycarbonate (PC) nanoparticles using supercritical CO_2 was developed. The objective of the present research work was to synthesize high molecular weight PC nanoparticles using transesterification between bisphenol-A (BPA) and diphenyl carbonate (DPC) in supercritical CO_2 which is an excellent plasticizing agent and a good solvent for phenol, a by-product of the reaction. Poly (propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) tri-block copolymer with CO_2-phobic anchor and CO_2-philic tail group was used as a stabilizer for the preparation of stable dispersions of BPA-DPC mixture in a CO_2 continuous phase. As the reaction was proceeding, phenol formed from the reaction was dissolved and diffused into supercritical CO_2 phase. The PC nanoparticles were isolated by simple venting of the supercritical CO_2 from the reactor. Spherical morphology of PC particles was confirmed by scanning electron microscopy. Particle size and morphology of PC particles were modified upon variation of the process conditions. The resulting PC particles with a nano-size of 30-140 nm have a high molecular weight (M_w) of 3.1 * 10~5 (g/mol).