| Pickering emulsion is composed of two immiscible phases where one kind of liquid is dispersed in another as droplets with the presence of solid particles.Pickering emulsions have been widely used in catalysis,separation,and biomedicine fields due to their high interfacial area,enrichment effect and easy to separate the emulsifiers.Traditional Pickering emulsifiers contain inorganic hard particles such as silica,Fe3O4,graphene oxide and so on,in recent years,organic soft matter such as microgel and polyelectrolyte complexes have been considered as Pickering emulsifiers.Polyelectrolyte complexes are a class of polymers with special properties formed by two oppositely charged polyions,there are many studies focused on the phase behavior of the complexation and aggregation in an aqueous solution,but that based on interfacial behavior at the oil-water interface is rarely.The hydrophilicity of the complex species formed by two oppositely charged species in aqueous solution can be changed by varying their types.Therefore,by changing the type of polyelectrolyte and adjusting the mixing ratio of cation to anion,the oil-water interfacial behavior of polyelectrolyte complexes can be simply adjusted,a new type of Pickering emulsifiers can be exploited.On this basis,functional species can be introduced into the oil-water interface by using functional substances as polyelectrolytes through simple complexation,then establish a new method for preparing micro-nano composite materials.To this end,this work was using polyelectrolyte complex to combine the copolymeric ionic liquid with various anions,constructing a stable Pickering emulsion system of various copolymeric ionic liquid based polyelectrolyte complexes,which proved that by changing the type of polyelectrolyte and adjusting the mixing ratio of cation to anion,the oil-water interfacial behavior of the polyelectrolyte complex can be adjusted,and the functional species can be simply introduced into the oil-water interface.The strategy of regulating and constructing the Pickering emulsion system probably becomes a new method for preparing micro-nano composite materials.The specific contents are as follows:(1)The regulation of oil-water interfacial behavior of polyelectrolyte complexes based on copolymeric ionic liquid.A copolymerized ionic liquid(PIL-co-PVIm)containing1-vinyl-3-ethylimidazole bromine and 1-vinylimidazole was used as a polycation,and sodium alginate(SA),sodium polystyrene(PSS),and sodium polyacrylate acid(PAA)were used as polyanions,and sodium 4-vinylbenzenesulfonate(Na VBS)was used as a small molecule anion,polyelectrolyte complexes can be formed by those two oppositely charged electrolytes at different charge molar ratio(Ncation/anion).The surface morphology and emulsification performance in different oil-water systems were evaluated by scanning electron microscope,Zeta potential analysis and optical microscope.The results showed that the polycation and polyanion alone cannot be used as emulsifiers.The polyelectrolyte complexes based on homopolymerized poly(1-vinyl-3-ethylimidazole bromine),and SA or PSS does not have the emulsification capability.However,after introducing 1-vinylimidazole as a comonomer,the polyelectrolyte complexes PIL-co-PVIm/SA and PIL-co-PVIm/PSS have excellent emulsification performance on toluene-water or hydrophobic ionic liquid 1-butyl-3-methylhexafluorophoaphate-water binary systems.By replacing the comonomer with 4-vinylpyridine,and then complexed with different polyanions,the polyelectrolyte complexes also have good emulsification capability at the non-stoichiometric ratios,amphiphilic nanosheet emulsifiers can also be obtained by drying the emulsions,and their thickness are remarkably decreased after emulsification,approximately ranging from 200 nm to 10 nm by manipulating the polyanions.The polyelectrolyte complex nanosheet at the oil-water interface(10 nm)is much thinner than that in the dispersion(500 nm).The results above proved that the strategy of varying the type of polyelectrolyte and adjusting the mixing ratio of cation to anion can change the hydrophilicity of polyelectrolyte complexes and realize the effective packing at the oil-water interface.(2)The introduction of phosphotungstic acid functional groups to the oil-water interface based on polyelectrolyte complexation.As acid catalysts with excellent performance,heteropolyacids have been widely used in different fields,the development of a new method that can simply introduce functional groups to the oil-water interface is the prerequisite for the construction of a special heterogeneous interfacial catalytic system.In this work,phosphotungstic acid(HPW)was used as a polyanion,after complex with copolymerized ionic liquid,the PIL-co-PVIm/HPW can be obtained,and then HPW can be simply introduced to the oil-water interface.The surface properties and emulsification performance of PIL-co-PVIm/HPW formed under different conditions were analyzed by infrared spectroscopy,scanning electron microscope,contact angle,Zeta potential and optical microscope.The results showed that the copolymerized ionic liquid and HPW were successful complexed,and HPW functionalized copolymerized ionic liquid at various Ncation/anion can be used to stabilize the water-toluene systems,but the emulsification capability is slightly different.After blast drying the emulsions,PIL-co-PVIm/HPW with sheet structure formed by disc-shaped or spherical particles can be observed.With the increase of the volume ratio of water to toluene,the emulsion stabilized by PIL-co-PVIm/HPW with Ncation/anion=1∶4 can realize phase reversion from w/o to o/w.PIL-co-PVIm/HPW have a good emulsification performance for toluene-water emulsions under acidic,neutral,and weak alkaline conditions,but the emulsion is demulsified under strong alkaline condition(p H=12),manifested the p H-responsibility of emulsions stabilized by PIL-co-PVIm/HPW.In addition,PIL-co-PVIm/HPW also exhibits a good emulsification effect on hydrophobic ionic liquid 1-butyl-3-methylhexafluorophosphate-water or paraffin-water binary system.The catalytic degradation of methyl orange(100-250 mg/L)can be achieved by the n-octane-water emulsion system constructed by PIL-co-PVIm/HPW within one hour.As a result,HPW was simply brought to different types of oil-water interfaces by complex with PIL-co-PVIm,and realized the interfacial catalytic degradation of methyl orange,this approach provides new ideas and technologies for the construction of the specific heterogeneous interfacial catalytic system.(3)Copolymerized ionic liquid induced the disaggregation of phthalocyanine and the electrochemical detection of dopamine by its complexes.The phthalocyanine and its derivatives have excellent optical,electrical,and catalytic properties,but the strong tendency of their molecules to aggregate in an aqueous solution limits their performance,therefore the disaggregation has been the priority problem for the application of phthalocyanine and its derivatives.In this work,tetracarboxy cobalt phthalocyanine(Co Pc)was used as a polyanion,after complexing with the copolymerized ionic liquid,the PIL-co-PVIm/Co Pc can be obtained.The aggregation states of PIL-co-PVIm/Co Pc at the aqueous solution and the oil-water interface were analyzed by UV absorption spectrum and scanning electron microscope.The results showed that Co Pc and PIL-co-PVIm/Co Pc complexes solid particles have monomeric phthalocyanine species,however,the cobalt phthalocyanine giving dimeric species in the aqueous solution,after complexing with PIL-co-PVIm at Ncation/anion=1:2,PIL-co-PVIm/Co Pc showed a high degree of monomeric phthalocyanine in aqueous solution.Under alkaline conditions,the PIL-co-PVIm/Co Pc complex with Ncation/anion=1∶2 has a higher degree of monomeric phthalocyanine in the aqueous solution with an increase of p H value,due to the dissociation of carboxylic acid in Co Pc promotes its complex with PIL-co-PVIm.At the same time,the monomeric cobalt phthalocyanine in this aqueous solution can be used to stabilize emulsions and give a high degree of monomeric phthalocyanine species at the toluene-water interface.The PIL-co-PVIm/Co Pc micro-nanosheets with different morphologies can be obtained after drying the complexes constructed under different circumstances.The glassy carbon electrode modified by PIL-co-PVIm/Co Pc was utilized to detect dopamine electrochemically,the electrode modified by the PIL-co-PVIm/Co Pc complex with Ncation/anion=1∶2 has fairly good performance.Therefore,the phthalocyanine molecules can be disaggregated at the aqueous solution and the oil-water interface,and the monomeric phthalocyanine molecule can be introduced to the oil-water interface by complexing with copolymeric ionic liquid,additionally,the PIL-co-PVIm/Co Pc can be used to detect dopamine electrochemically. |
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