No abstract

Amphiphilic block copolymers poly(ethylene glycol)-block-oligo(vinyl acetate) (PEG-b-OVAc) and OVAc-b-PEG-b-OVAc have been demonstrated to be effective surfactants for CO 2 -in-water (C/W) emulsions. However, the high cost and difficulty of synthesis process can render the economics of CO 2 process unfavorable. In this work, by reversible addition-fragmentation chain transfer (RAFT) polymerization, a series of well-defined CO 2 -philic triblock copolymers X-OVAc-b-PEG-b-OVAc-X (where X stands for xanthate group) were synthesized. The structures and molecular weights of these copolymers were characterized by 1 H NMR and GPC. The results of GPC analysis exhibited relatively narrow polydispersity (PDI < 1.35). The process of preparation of X-OVAc-based surfactants was much more simple, inexpensive and also easy to control, which could promote industrial-scale applications. The X-OVAc-based surfactants were found effectively to produce highly concentrated stable C/W emulsions. Porous emulsion-templated materials were prepared by the polymerization of the continuous phase of C/W emulsions. The open-cell morphology of the emulsion-templated materials was evidenced by scanning electron microscope. To tune the morphology of the porous structures, the influence of the surfactant concentration and molecular weight of OVAc block were also investigated. It was shown that X-OVAc-based surfactants can outperform perfluorinated surfactants and approach OVAc-based surfactants for such applications.

Porous cross-linked poly(N-isopropylacrylamide) (PNIPAM) was prepared using high internal phase emulsions as templates. The materials could absorb a large volume of water and swell largely at room temperature. When the aqueous phase was heated above the lower critical solution temperature (LCST) of PNIPAM, the swollen structure could contract and squeeze some of the absorbed liquids out. This capability was utilized in the uploading at room temperature and then release of polystyrene colloids by increasing the temperature above the LCST. The thermoresponsive porous PNIPAM acted like a pump to load and then release the polymer colloids. The multicycles of loading and release were demonstrated to show its efficiency. Importantly, it showed that most of the PS colloids from the second upload onward could be released during the heating cycle.

No abstract

The electrochemistry of glassy melt-spun 60 atom percent (a/o) Ni-40 a/o Nb was investigated at moderate temperatures in various aqueous media. The alloy was very corrosion resistant to most acids and alkalis, but it was attacked by aqueous HF. Cyclic voltammograms of the glassy alloy in 15M NaOH indicated the existence of a thin nickel oxide corrosion layer from which niobium was absent. Linear sweep vottammetry in the oxygen evolution region, constant current chronopotentiometry, and rest potential decay measurements confirmed that the alloy surface in alkali consisted of nickel oxides. Chronopotentiometry in 0.5M H2SO4 at 30~ indicated the formation of a thin niobium oxide corrosion film which did not prevent oxygen evolution. Anodization in concentrated neutral KC1 caused severe corrosion. On cathodization in acid, the glassy alloy absorbed ca. 14 a/o hydrogen and was severely embrittled. Attempted hydrogen permeation experiments caused ribbon fracture; as-quenched and low temperature-annealed glasses behaved differently in this respect. * Electrochemical Society Active Member. Key words; glassy metal, NI-Nb alloy. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.126.162.126 Downloaded on 2015-03-14 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.126.162.126 Downloaded on 2015-03-14 to IP Vol. 13I, No. 5 GLASSY 60Ni-40Nb 1001 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.126.162.126 Downloaded on 2015-03-14 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.126.162.126 Downloaded on 2015-03-14 to IP