Small angle neutron scattering and atomic force microscopy studies of complex polymers and polymer interfaces.

摘要

Structural studies have been carried out on complex polymers at different interfaces. Three different systems have been studied: (I) A water/sodium di-2-ethxylsulfosuccinate (AOT)/decane microemulsion with addition of a polyethylene oxide (PEO)-poly-dimethylsiloxane (PDMS)-PEO triblock copolymer; (II) Perfuorosulfonimide ionomer solutions and thin films; (III) Partially sulfonated styrene-ethylene copolymer membranes. X-ray and neutron scatterings have been used to study the solutions. The thin films have been studied by atomic force microscopy.; In system I, the triblock polymer is at an interface with microemulsion droplets. The polymer-free microemulsion forms spherical water droplets at the studied compositions, and the droplet size can be controlled by the water-to-surfactant molar ratio. The PEO part of the triblock polymer is soluble in the water phase while the PDMS block is soluble in the decane phase. Small angle neutron scattering (SANS) study revealed that addition of the copolymers induced a phase transition from spherical droplets of water-in-oil to a bicontinuous phase.; Perfluorosulfonimide ionomer has been studied in solutions and in thin films. The evolution of structure of the ionomer in polar solvents, from isolated molecules to micellar association was studied by SANS. At low concentration, the polymers exhibit expanded configuration whereas aggregation takes place at higher concentration. Thin films cast from solutions are strongly affected by the nature of the solvent and the confinement of the interface. The micelles form in solution are trapped by the presence of the interface. At large length scales, the films exhibit multiple-scale periodicities. The as-cast film is in meta-stable state and undergoes rearrangement upon annealing, changing the surface morphology.; The membrane of partially sulfonated styrene-ethylene copolymer has been studied at the interface with water. The fully hydrated membrane forms a bicontinuous network of hydrophilic and hydrophobic domains, where the sulfonated groups serve as the interface.