Synthesis and Properties of Amphiphilic Polymers

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This 2-year Japan-U.S.bilateral research project has been directed to "amphiphilic polymers", or macromolecules consisting of both hydrophilic and hydrophobic moieties, for which efforts have been focused on : (a) precision sample syntheses ; (b) their behavior in solution and at surface or interface ; (c) factors affecting their hydrophilic and hydrophobic interactions ; and (d) relations between their spatial shapes and functions. A brief summary follows :1.Synthesis of Amphiphilic PolymersFour series of well-defined amphiphilic polymers have been synthesized by the living cationic polymerization developed by the Japanese members :(A) AB-block copolymers of 2-hydroxyethyl and 2-phenoxyethyl vinyl ethers ;(B) AB-block copolymers of 2-hydroxyethyl and n-butyl vinyl ethers ;(C) Partially deuterated analogs of block copolymers A and B where the phenyl and the n-butyl pendant groups are deuterated, respectively ;(D) Tetraarmed block copolymers of vinyl ether and stirene derivatives.2.Ligh … More t Scattering and X-Ray Scattering AnalyzesSolubilization of hydrophobic dyes into water by these polymers confirmed that they are amphiphilic and thus form micelles, which were further analyzed by scattering methods :(a) Dynamic light scattering (DLS) for the micelle sizes ;(b) Forced Rayleigh scattering for the diffusion constants (by the American members) ;(c) Small-angle X-ray scattering (SAXS) for the shape and number of the micelles.For example, the DLS analysis (a) of the 4-arm polymers D showed their sharp response to solvent polarity, unimers in ethanol and micelles in chloroform. The SAXS data (c) for the linear polymers A and B indicated that increasing polymer concentration increases the number of micelles without changing their shapes.3.Neutron Scattering AnalysisSmall-angle neutron scattering (SANS) was applied to the partially deuterated amphiphiles C in D_2O/H_2O mixtures for the contrast variation method. Dependence of SANS profiles on the solvent composition revealed core-shell architectures of the block polymers, the shapes of which change from spherical to ellipsoidal on increasing length of the hydrophobic segments.4.Surface and Interface AnalysisEffective surface activity of polymers A and B were shown by clear reduction of the surface and interfacial tensions of water in their presence at low concentrations. These amphiphiles also interact with silica surface ; the strength and distance of the interaction was evaluated by evanescent light wave scattering. Less