Self-assembled Micelle Of Branched Amphiphilic Copolymer And Its Emulsifying Propetry

In recent years, the self-assembled micelle based on amphiphilic copolymer appears tobe a good model of particulate emulsifier to elucidate the relationship among the structure ofcopolymer, structure of polymeric self-assembled micelle and its emulsifying property,because of the excellent controllability, tailor-ability and multifunctionality of the polymericself-assembled micelle, which has attracted many attention. Studies have shown that theself-assembled micelle with moderately swollen structure, compact micelle core twined bylots of polymeric chain ends, combines the advantages of solid particulate emulsifiers andpolymeric surfactants, possessing excellent emulsifying property. Compared with linearamphiphilic copolymer, branched amphiphilic copolymer has multiple side chains and itsself-assemled micelle employed as particulate emulsifier may enhance the cooperativestability effect of “polymer surfactant-particulate emulsifier”, which contributes to thepreparation of high-efficient particulate emulsifiers. However, most polymeric self-assembledmicelles employed as particulate emulsifier are prepared by linear amphipathic polymer,while there are little reports about utilizing branched polymer to prepare polymericself-assembled micelles serving as particulate emulsifiers, let alone exploring the influencingfactors of emulsifying property of branched polymeric self-assembled micelles. Additionally,the comparation of linear and branched polymeric structure, the structure and emulsifyingproperty of their micelles are seldom found in researches. This paper invesgates theinfluencing factors of emulsifying property of self-assembled micelles based on branchedcopolymer, as well as the difference of emulsifying property between linear and branchedpolymeric micelles as follows:A branched amphiphilic random copolymer poly(styrene-co-acrylic acid)(BPSAA) wasprepared by complete hydrolysis of the branched random copolymerpoly(styrene-co-tert-butyl acrylate)(BPSTBA) which was synthesized from styrene, tert-butylacrylate,1-(chloromethyl)-4-ethenyl-benzen by atomtransfer radical polymerization (ATRP)method. The spherical BPSAA micelle utilized as particulate emulsifiers was prepared byself-assembly method in selective solvent DMF/H2O to stabilize oil-water system. Theinfluencing factors of emulsifying property and stimulative responsibility of BPSAA micelleswere invegated. The results showed that introduce of branched polymer structure can increasethe hydrophilic polymeric chain ends (AA) twined on the surface of the micelle, facilitatingthe hydrophily of BPSAA micelles, which is beneficial to the swelling of BPSAA micelles.The cooperative stability effect of “polymer surfactant-particulate emulsifier” of swollenstructure of BPSAA micelle improves its emulsifying property. The change of externalenvironment (pH、NaCl) can lead to the structural change of BPSAA micelles, and the emulsion stabilized by BPSAA is pH-and NaCl-responsive. BPSAA micelles as particulateemulsifiers can stabilize many cosmetic oil like white oil, dicaprylyl carbonate, Propylheptylcaprylate, silicone oil, isooctyl palmitate, sensoft oil, etc.Spherical self-assembled micelles based on branched amphiphilic alternating copolymerpoly(styrene-alt-maleic anhydride)(BPSMA) was prepared in selective solvent DMF/H2Oand was utilized as particulate emulsifiers to stabilize oil-water system. The relationshipamong branching structure of copolymer, micellar structrue and emulsifying property ofBPSMA micelle were further invesgated. The influence of stimulative responsibility (pH andNaCl salt) on structure and emulsifying property of BPSMA micelle were explored. Thedifference in micllar structure and emulsifying property of linear poly(styrene-alt-maleicanhydride)(LPSMA) and BPSMA micelles was compared. The results showed that introduceof branched polymer structure can not only increase the hydrophilic polymeric chain ends(MAn) twined on the surface of the BPSMA micelle, facilitating the hydrophily of micelleand swelling of BPSMA micelles; but also enhance the compact structure of BPSMA micelle,so that the moderately swollen BPSMA micelle can’t dissolve and scatter easily like LPSMAmicelle, presenting more remarkable cooperative stability effect of “polymersurfactant-particulate emulsifier”. Therefore, BPSMA micelle possesses better emulsifyingefficiency, and the emulsion stabilized by BPSMA micelle exhibits better long-term stability,compared with LPSMA micelle. The larger degree of braching of BPSMA is, the higheremulsifying efficiency of BPSMA micelle is. The concentration of NaCl brings about littleimpact on the micellar structure and the emulsifying property of BPSMA micelles whiledramatic influence on the LPSMA micelles. The diameter of LPSMA micelle decreases as theNaCl concentration increases, the emulsifying property improved along with the droplets ofemulsion decrease. Additionally, the emulsion stabilized by BPSMA micelles is pH-dependent.BPSMA micelles can also stabilize other cosmetic oils like dicaprylyl carbonate, propylheptylcaprylate, silicone oil, isooctyl palmitate and sensoft oil, etc.