title: Self-assembly of charged amphiphilic diblock copolymers with insoluble blocks of decreasing hydrophobicity: from kinetically frozen colloids to macrosurfactants.
abstract: We have investigated the self-assembly properties in aqueous solution of amphiphilic diblock copolymers with insoluble blocks of different hydrophobicity and demonstrated that the condition to obtain dynamic micelles is to design samples with insoluble blocks of low enough hydrophobicity. We focus here on results with new water-soluble amphiphilic diblock copolymers poly(diethyleneglycol ethylether acrylate)-b-poly(acrylic acid), or PDEGA-b-PAA. The physical characteristics of PDEGA-b-PAA micelles at high ionization have been determined by small angle neutron scattering (SANS). We show that PDEGA-b-PAA samples form micelles at thermodynamic equilibrium. The critical micelle concentrations (CMCs) decrease strongly with ionic strength and temperature due to a solvent quality decrease for, respectively, the corona and the core. This behavior of reversible aggregation is remarkable as compared to the behavior of kinetically frozen aggregation that has been widely observed with samples of similar architecture and different hydrophobic blocks, for example, poly(styrene)-b-poly(acrylic acid), PS-b-PAA, and poly(butyl acrylate)-b-poly(acrylic acid), PBA-b-PAA. We have measured the interfacial tension between water and the homopolymers PDEGA and PBA at, respectively, 3 and 20 mN/m at room temperature, which permits one to estimate the energy cost to extract a unimer from a micelle. The results are consistent with a micelle association that is fast for PDEGA-b-PAA and kinetically frozen PBA-b-PAA. Hence, PDEGA-b-PAA samples form a new system of synthetic charged macrosurfactant with unique properties of fast dynamic association, tunable charge, and water solubility even at temperatures and NaCl concentrations as high as 65 °C and 1 M.
authors.affiliation: Complex Fluids Laboratory, CNRS UMR 166, Rhodia Research Center, 350 George Patterson Boulevard, Bristol, Pennsylvania 19007, United States.
authors.forename: M
authors.initials: M
authors.lastname: Jacquin
authors.forename: P
authors.initials: P
authors.lastname: Muller
authors.forename: H
authors.initials: H
authors.lastname: Cottet
authors.forename: O
authors.initials: O
authors.lastname: Théodoly
mesh_terms: D000179:Acrylates / Q000737:chemistry*; D000180:Acrylic Resins / Q000737:chemistry*; D003102:Colloids; D005615:Freezing; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008823:Micelles; D033363:Neutron Diffraction; D009994:Osmolar Concentration; D011092:Polyethylene Glycols / Q000737:chemistry*; D053838:Scattering, Small Angle; D012995:Solubility; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D000179:Acrylates; D000180:Acrylic Resins; D003102:Colloids; D008823:Micelles; D013501:Surface-Active Agents; C535257:poly(diethylene glycol ethyl ether acrylate); D014867:Water; D011092:Polyethylene Glycols; C006903:carbopol 940