Self-Assembly and Emulsification\nof Poly{[styrene-<i>alt</i>-maleic acid]-<i>co</i>-[styrene-<i>alt</i>-(<i>N</i>-3,4-dihydroxyphenylethyl-maleamic\nacid)]}

Abstract

Self-assembled polymeric micelles can be used as efficient\nparticulate\nemulsifiers. To explore the relationship between the structure and\nthe oil–water interfacial behavior of the micelle emulsifiers,\na new type of amphiphilic random copolymer, poly­{(styrene-<i>alt</i>-maleic acid)-<i>co</i>-[styrene-<i>alt</i>-(<i>N</i>-3,4-dihydroxyphenylethyl-maleamic acid)]} (SMA–Dopa),\nwas synthesized, self-assembled into micelles, and used as emulsifiers.\nSMA–Dopa was synthesized via an aminolysis reaction between\ndopamine and commercial alternating copolymer poly­(styrene-<i>alt</i>-maleic anhydride) (SMA). Dopamine moiety facilitated\nthe self-assembly of the SMA–Dopa in selective-solvent into\nstable micelles, and increased the adsorption of the SMA–Dopa\nat the oil–water interface. Additionally, the structural transition\nof the self-assembled SMA–Dopa52 micelles in response to pH\nand salinity changes were confirmed by means of TEM, AFM, DLS, aqueous\nelectrophoresis techniques, potentiometric titration, and pyrene fluorescence\nprobe methods. Micelles shrunk with increasing salinity, and flocculation\nof the shrunken primary micelles occurred at salt concentration exceeding\n0.1 M. The micelles swelled with increasing pH, and the disassociation\nof the SMA–Dopa52 micelles occurred at pH above approximately\n6.5. The structure of the micelles plays a crucial role in the oil–water\ninterfacial performance. Micelles with various structures were used\nas emulsifiers to adsorb at the styrene–water and toluene–water\ninterfaces. The emulsifying characteristics demonstrated that self-assembled\nSMA–Dopa52 micelles with moderately swollen structure (at 2 <\npH < 6) combine the advantages of the solid particulate emulsifiers\nand polymeric surfactants, possessing excellent emulsifying efficiency\nand good emulsion stability. Moreover, the emulsifying performance\nof the SMA–Dopa52 micelles could be enhanced by the addition\nof salt.