| Emulsions are a class of disperse systems consisting of two immiscible liquids. As one of the most important part of emulsion, the emulsifier has been paid more and more attention. Compared with the low-molecular-weight surfactants, the macromolecular surfactants have the advantages of low critical micelle concentration and low mobility. When as emulsifiers for emulsions formation, lower emulsifier content is usually required. Compared with the linear amphiphilic block polymers, non-linear amphiphilic copolymers show more excellent emulsifier performances. In this study, synthesis and application as emulsifier of Y-shaped amphiphilic AB2 miktoarm star copolymer and double-brush amphiphilic copolymers were presented. The main contents were summarized as follows:(1) Dual responsive macroemulsion stabilized by Y-shaped amphiphilic AB2 miktoarm star copolymers. Firstly, amphiphilic Y-shaped AB2 miktoarm star polymeric emulsifier composed of poly(N,N-dimethylaminoethylmethacrylate)(PDMAEMA) and polystyrene(PS) arms, was synthesized by sequential reversible addition-fragmentation chain transfer(RAFT) polymerization of styrene monomer and atom transfer radical polymerization(ATRP) of N,N-dimethylaminoethyl methacrylate(DMAEMA) monomer. The structure and the molecular weight as well as the molecular weight distribution were carefully characterized by 1H NMR and GPC, respectively. The obtained PS-(PDMAEMA)2 miktoarm star polymers were then applied as polymer emulsifiers for both o/w and w/o macroemulsions formation, and stabilized macroemulsions could be produced at a lower emulsifier content. Meanwhile, the emulsifying performance of PS-(PDMAEMA)2 miktoarm star polymer and the stimulus-responsibility of the macroemulsion were also investigated. The PS-(PDMAEMA)2 stabilized o/w macroemulsion showed pH-induced deemulsification and temperature-induced phase inversion.(2) Efficient synthesis of narrowly dispersed amphiphilic double-brush copolymers through the radical polymerization reaction of macromonomer micelle emulsifiers at oil-water interface. Well-defined amphiphilic double-brush copolymers(DBCs) with narrow molecular weight distributions were efficiently synthesized by radical polymerization of macromonomers directed by Pickering emulsion template at oil-water interface. Firstly, well-defined poly(methyl methacrylate)-b-poly(N,N-dimethyl acryamide)(PMMA-b-PDMA) diblock macromonomer carrying a pendent methacryloyl(MA) group at the block junction(MA-PMMA-b-PDMA) was synthesized through sequential atom transfer radical polymerization(ATRP) and reversible addition-fragmentation chain transfer(RAFT) polymerization, followed by an acrylation functionalization reaction. The MA-PMMA-b-PDMA macromonomer could self-assemble into core-shell micelles with hydrophobic PMMA-based cores, hydrophilic PDMA shells and MA groups at core-shell boundary. The as-formed core-shell micelles were then employed as emulsifiers for the formation of stabilized oil-in-water(o/w) Pickering emulsion, in which the macromonomer micelles were locked at the oil-water interface and presented Janus-like conformation. At last, the conventional radical polymerization reaction was carried out for the MA groups of the macromonomer micelles absorbed at the oil-water interface using azobiisobutyronitrile(AIBN) pre-encapsulated in the Pickering emulsion oil droplets as initiator, leading to well-defined PMA-g-PMMA/PDMA DBCs with narrow molecular weight distributions. The as-formed DBCs showed higher degrees of polymerization of backbones than the DBCs synthesized by micellar polymerization of the macromonomer in pure water, presumably due to the facilitated propagation reaction between the neighboring micelles in the former cases. The macromonomers and DBCs were carefully characterized by various instrumental analytical techniques. |
