Synthesis of Self-demulsification Thermosensitive Polymeric Surfactants and Their Application in Emulsion Polymerization
This study proposes utilizing thermosensitive surfactants,referred to as"environmentally responsive surfactants,"as emulsifiers for addressing the complexity of demulsification and separation processes after emulsion polymerization reactions.A series of polyethylene glycol-poly(N-isopropylacrylamide)(PEG-b-PNIPAM)block copolymers with various degrees of polymerization were synthesized via atom transfer radical polymerization(ATRP).The PNIPAM segments within the copolymers exhibit thermosensitive behavior,possessing a lower critical solution temperature(LCST)at 32 ℃,enabling the control of hydrogen bond formation and rupture with water molecules based on temperature variations.Consequently,the PEG-b-PNIPAM block copolymers display hydrophilic properties at room temperature and amphiphilic properties in the range from 35 ℃ to 80 ℃.Surface tension measurements at different concentrations confirmed the low critical micelle concentration(CMC)of the PEG-PNIPAM block copolymers,with a minimum value as low as 9.1 0× 10-3 g/L.Evaluations of particle size distribution and emulsification performance validated its applicability as an emulsifier in emulsion polymerization within the aforementioned temperature range.Microscopic observations of latex particles corroborated the precise occurrence of emulsion polymerization,displaying a relatively uniform particle size distribution in the resulting polymer.Upon completion of the emulsion polymerization reaction,the need for additional agents such as demulsifiers or physical methods like mechanical stirring was obviated.Merely lowering the reaction system to room temperature facilitated demulsification,yielding the desired polymer products.Further,rapid demulsification could be achieved by cooling the reaction system at lower temperatures(3-8 ℃).Utilizing PEG-b-PNIPAM block copolymers as surfactants allowed the temperature-controlled emulsification and demulsification processes,significantly streamlining the emulsion polymerization process,reducing costs,and enabling environmentally friendly production practices.
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维普
