Hydrocarbon Particle Stabilizers Applied On Dispersion Polymerization In Supercritical Carbon Dioxide

The destructive of volatile organic compounds have prompted considerable worldwide concern.Supercritical carbon dioxide is new green solvent that bears a large amount of traits with no flammability,negligible toxicity,naturally abundant,easily isolated by simple depressurization and so on.Unfortunately,most high molecular weight of polymers cannot dissolve in ScCO₂.Therefore,it is necessary that high efficient CO₂-philic stabilizer is imperative to dispersion polymerization in ScCO₂ polymerization medium.So far,most CO₂-philic stabilizers are expensive,the complex synthetic routes,difficult purification process as well as wasting large amount organic solvent.In this thesis,we propose a new method that particles have effect on stabilizing polymer particle to successfully prepared high molecular weight,high yield,flowing PMMA powder by dispersion polymerization at warm condition in the ScCO₂.The main contents are list as follows:?1?SiO₂ particle as stabilizer is applied in dispersion polymerization of MMA in ScCO2,aiming at studying the particle stabilizing scheme on polymerization process in ScCO₂.PMMA coagulated powder based on non CO₂-philic SiO₂ powder modified with ethoxy group is synthesized in ScCO_2.The average Mn is about 3.2 x 10⁵ g mol^-1 and the most yielding is above 85.6%.Microporous polymer or polydivinyl benzene as stabilizer,which can adsorb CO₂,applied in dispersion polymerization of MMA in ScCO₂ can get the light yellow fine PMMA and white fine PMMA powder.Molecular weight and yield of the PMMA particles increase with the concentration of stabilizer increasing.?2?In order to improve the efficiency of particle stabilizer,we design the CO₂-philic particle stabilizer that is alternating copolymer of maleic anhydride?MAn?/vinyl acetate?VAc?.Then,we can adjust the concentration of stabilizer,mixing rate,pressure,kinds of initiator to improve the morphology of PMMA.The average molecular weight is close to3.0 x 10⁵ g mol^-1 and the maximum yield is 96.2%.The best polymerization condition is1500 r/min and BPO-DMA redox initiator.Pressure has no effect on the morphology of PMMA powder.The conception of powders applied in ScCO₂ can break the limitation of previous research and provide the basis of dispersion polymerization in the ScCO₂ in the future.