| Polymer surfactant is a kind of amphiphilic compounds which both have hydrophobic group and hydrophilic groups,with emulsification,demulsification,sterilization and other functions and is widely used in scientific research and industrial fields.In most practical applications,surfactants are only required to play a role at a certain stage.After the end of the stage,they were required to be removed from the system or to be reactivated to reduce the side effects due to its residues.Therefore,the design of switchable polymer surfactant is of great significance.CO2-switched polymer surfactants are widely concerned because of their environmentally friendly and recyclable advantages.However,most of the researches on CO2-switched polymer surfactants have been focused on the study of the change of the aqueous solution aggregation structure of surfactants at the present while the research of CO2-switched emulsions is out of focus,and most polymer surfactants have used blocks and other complex methods to synthesize the polymer.In order to make the operation easier and more suitable for practical applications,in this paper,a kind of CO2-switched polymer surfactant was prepared by simple random copolymerization of N,N-Diethylaminoethyl methacrylate?DEAEMA?and sodium vinyl sulfonate?SVS?,and its performance was studied.Meanwhile,the surfactants were prepared by emulsification of water / liquid paraffin system and water / toluene system.And the emulsions and demulsification behaviors of the surfactants and its solvent systems were studied.The main contents of this paper include the following four parts:1.PDEAEMA-co-PSVS nanoparticles were prepared by random copolymerization with DEAEMA and SVS as raw materials.The effects of monomer ratios on the particle size,surface/interface activity,emulsifying performance of polymer particles were studied.The results showed that when the monomer ratio?mol SVS: mol DEAEMA?is 1: 1,the particle size was about 118 nm and well-distributed,and led to the reduction of the surface tension of water to 37.279 m N/m and that of water / liquid paraffin to 5.492 m N/m.Moreover,The emulsion prepared with the particles as the sole emulsifier is the most stable.2.The CO2-switchable performance and the change of particle response of the polymer synthesized under the best ratio?1:1?were studied.The response ability of the polymer particles to acid and base conditions was investigated.The results showed PDEAEMA-co-PSVS aqueous solution changed from milky white to a clear condition when CO2 was bubbling into the solution,and the solution conductivity increased from 191 ?S/cm to 1290 ?S/cm,and the p H decreased from 8.8 to 6.5.When the solution was heated to 60?and bubbling N2,the solution returned to its original condition,and its conductivity and p H were returned to their initial values.These facts revealed that the polymer has a fast and reversible CO2-switchable performance.Variation of agglomeration and dispersion of the particles in CO2 and N2 environments were investigated by Cryo-TEM and particle size analysis.The polymer particles were stable in the strong alkaline,and disperse more thoroughly in strong acid environment.3.The emulsification ability of the polymer to water / liquid paraffin system and the CO2-switchable performance of its emulsion were studied.The results showed that PDEAEMA-co-PSVS has a strong interfacial activity and could effectively reduce the interfacial tension between water / liquid paraffin.With the increase of the concentration of polymer in the system,the interfacial tension value gradually decreased.When the concentration is higher than 0.2 wt%,the rate of interfacial tension decreasing was slowed down.Aqueous / liquid paraffin emulsion was prepared with PDEAEMA-co-PSVS as a sole emulsifier,which was oil-in-water?O/W?type.The emulsion was allowed to stand for 3weeks and the appearance was not changed.The microscopic observation showed no significant difference in the emulsion droplet from the original state.When PDEAEMA-co-PSVS concentration is higher than 0.2 wt%,the resulting emulsion was stable and homogeneous.With the reduction of the amount of liquid paraffin,a stable emulsion could still be formed,but when the ratio of liquid paraffin to water is greater than 1: 1,the formation of emulsion was instable.The emulsion prepared by the polymer has a good CO2-switchable performance,demulsificated quickly,thoroughly and completely.With the increase of the concentration of PDEAEMA-co-PSVS in the system,the demulsification rate of the emulsion would be slowed down,but all could still achieve complete demulsification.Different oil content in the emulsion system could all achieve demulsification.4.The emulsification ability of the polymer to water / toluene system and the CO2-switchable performance of its emulsion were studied.The results showed that,PDEAEMA-co-PSVS exhibited strong interfacial activity,and was able to decrease interfacial tension between water / toluene system even at low concentrations.When the concentration was higher than0.25 wt %,the rate of the decreasing of interfacial tension was slowed down,and the interfacial tension value kept at approximate 4.9 m N/m.Aqueous / toluene emulsion was prepared with PDEAEMA-co-PSVS as a sole emulsifier,which was oil-in-water?O/W?type.The emulsion was allowed to stand for 3 weeks and the appearance was not changed.A stable emulsion could be prepared under different ratio of oil and water.When the concentration was lower than 0.025 wt %,the emulsion could not be formed,and instable emulsion could be formed with the increasing of the concentration.When the concentration was higher than 0.25 wt %,the stable emulsion could be formed and was well-distributed.The emulsion prepared the polymer particles exhibited well CO2-switchable performance,demulsificated quickly and was able to completely recover. |
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