Electrical response characterization of PVA–P(AA/AMPS) IPN hydrogels in aqueous Na2SO4 solution

Interpenetrating polymer networks (IPN) hydrogels composed of poly(vinyl acohol) (PVA) and poly(acrylic acid-co-2-acrylamido-2-methyl propyl sulfonic acid) (P(AA/AMPS)) were synthesized by solution polymerization. The IPN hydrogels were characterized using Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD). The results indicated that strong hydrogen bond was formed between PVA and P(AA/AMPS), and the crystallinity of PVA in IPN hydrogels was declined significantly. The swelling/deswelling properties of IPN hydrogel in aqueous Na₂SO₄ solution were studied. When a sheet of water swollen IPN hydrogel (all the samples were swollen in deionized water) was placed in aqueous Na₂SO₄ solution, the IPN hydrogel shrunk. However, if a voltage was applied, the IPN hydrogel shrunk at high concentration of Na₂SO₄ solution, but swelled at low concentration. The results show that the critical concentration of Na₂SO₄ solution is about 0.005 mol/L. The stimuli response of the IPN hydrogel in electric field was also investigated. When water swollen samples were placed between a pair of electrodes in aqueous Na₂SO₄ solution, the IPN hydrogel showed significant bending behavior upon the application of an electric field. The bending direction of the IPN hydrogel depends on the concentration of Na₂SO₄ solution. At high concentration the IPN hydrogel bended toward anode, contrarily, at low concentration the IPN hydrogel bended toward cathode. The critical concentration of Na₂SO₄ solution is also about 0.005 mol/L. Further investigation showed that the gel component, concentration of aqueous Na₂SO₄ solution and the applied voltage influenced the bending speed of IPN hydrogel.     

The reversible binding of hydrophobically end-capped poly(ethylene glycol)s to poly-β-cyclodextrin-coated gold surfaces: a surface plasmon resonance investigation

Polymers of β-cyclodextrin (β-CD) bearing amino groups (poly-β-CD-NH₂) were grafted to gold surfaces by two different procedures. Hydrophobically end-capped model-polymers were adsorbed onto resulting (poly-β-CD-NH₂)-coated sensor chips by formation of inclusion complexes. Their adsorption onto the surface was followed in real time by surface plasmon resonance (SPR). Multilayered structures obtained by inclusion of adamantyl-modified poly(ethylene glycol)s (Ad-PEG) into immobilized β-cyclodextrin cavities were highly stable in aqueous media. Conditions leading to the regeneration of initial (poly-β-CD-NH₂)-coated surfaces were studied by SPR. Regeneration by competitors such as polymers of β-cyclodextrin was possible. However, it was found to be a complex mechanism involving two opposite phenomena depending on the structure and composition of the (poly-β-CD-NH₂) layer. Complete desorption of the bound Ad-PEG layer was also observed after exposure of the multilayered structures to organic solvents or sodium dodecylsulfate (SDS).     

The crystal structures of some RM and RM2 compounds (where R=rare earth metal and M=non - rare earth metal)

The non-cubic crystal structures of YIn, YPd and YAu are reported for the first time. YIn has the disordered tetragonal L1₀ CuAu-type structure, and both YPd and YAu are isostructural with the orthorhombic B33 CrB -type structure. The lattice parameters for some C15 MgCu₂-type Laves phase (Tb_xDy_1−x)Al₂ alloys (x=0.25,0.50,0.75$x=0.25,0.50,0.75$ and 1.0) have been measured and are found to vary linearly with composition between x=0.25$x=0.25$ and 1.0.