Preparation And Performance Of Thermo-responsive Surfactants PEG-b-PNIPAM

The thermo-responsive surfactant is a kind of surfactant with potential application value,which can realize the emulsification and demulsification reversibly by changing the temperature of the oil-water system.The strong temperature adaptability and good performance of the thermo-responsive surfactants are one of the important prerequisites for its application in the enhanced oil recovery process,in which different temperature is required for the emulsification and demulsification process,respectively.This thesis focuses on the synthesis and performance of thermo-responsive nonionic surfactant PEG-b-PNIPAM.The nonionic surfactants（PEG-b-PNIPAM and PNIPAM-b-PEG-b-PNIPAM）containing thermo-responsive blocks were firstly synthesized as well as the anionic surfactant（PNIPAM-COONa）.On basis of a comparison in emulsification performance of various surfactants,the PEG-b-PNIPAM was found to have a superior emulsifying ability and a more remarkable thermo-responsive performance.According to the effect of concentration on aggregates state and the thermo-responsive performance of PEG-b-PNIPAM,a thermo-responsive mechanism of the surfactant in oil-water system was proposed.The block copolymer at higher concentration can self-assemble to form colloidal particles through the physical crosslink in water when the temperature rises above Tcp（temperature of cloud point）,which help producing a Pickering emulsion in the oil-water system.When the temperature is lowered to Tcp,the colloidal particles dissociate and dissolve in the water rapidly,resulting in fast demulsification.For precisely tuning the cloud point temperature,this thesis optimized Single Electron Transfer-Living Radical Polymerization（SET-LRP）process to realize a rapid polymerization of PEG-b-PNIPAM in aqueous solution,which ensured a narrower molecular weight distribution of the polymer.With the optimized synthesis method,a series of PEG₄₅-b-PNIPAM_X（X=17,36,65,73,and 107）surfactants were successfully synthesized by controlling the amount of added NIPAM.Therefore,the cloud point temperature of PEG-b-PNIPAM can be adjusted due to the different PNIPAM content.It shows that the lower the PNIPAM content in PEG-b-PNIPAM,the higher the cloud point temperature.In addition,PEG-b-PNIPAM shows a certain thermo-responsive performance in both dodecane-water and crude oil-water systems,indicating that PEG-b-PNIPAM,as a kind of thermo-responsive surfactants,have potential application prospects in the field of enhanced oil recovery.