SYNTHESIS OF POLYSTYRENE PARTICLES IN SUPERCRITICAL CARBON DIOXIDE USING NOVEL SURFACTANTS
Supercritical carbondioxide (SCCO2) can be advantageously used as a “green solvent” for various processes over the traditional organic and aqueous solvents. We report here the free radical dispersion polymerization of styrene in SCCO2. The process used novel surfactants, polysiloxane-polystyrene diblock copolymers for stabilizing the monomer dispersion in the SCCO2. AIBN was the initiator for the process. This investigation studies the use of polystyrene-b-poly(dimethylsiloxane) (PS-b-PDMS) and polystyrene-b-poly(methylphenylsiloxane) (PS-b-PMPS) as surfactants and their effect on properties of the product such as particle morphology, size, size distribution and molecular weight distribution. The chemical conversion of styrene to polystyrene was observed from Nuclear Magnetic Resonance (NMR) Spectroscopy and Infrared (IR) Spectroscopy. Typical Number Average Molecular Weight, Mn obtained for the polystyrene from Gel Permeation Chromatography (GPC) was ~ 7000 g/mol and the polydispersity index was ~ 2.0. The Differential Scanning Calorimetry (DSC) and thermogravimetric analysis (TGA) behavior confirmed that polystyrene synthesized here was similar in properties to a polystyrene standard of similar molecular weight. The Environmental Scanning Electron Microscopy (ESEM) revealed that the polystyrene particles were spherical in shape and their size ranged between 5-10 microns.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:supercritical carbon dioxide polystyrene poly dimethylsiloxane methylphenylsiloxane
Date of Publication:01/01/2004