Biennial Report 2005-2007 - Saha Institute of Nuclear Physics

152 Biennial Report 2005-075.1.2.3 Titanium-rich highly ordered mesoporous silica synthesized by using a mixedsurfactant systemA new titanium-rich highly ordered 2-D hexagonal mesoporous titanium silicate has been synthesizedusing a mixture of cationic (cetyltrimethylammonium bromide, CTAB) and non-ionic (Brij-35,C 12 H 25 -(OC 2 H 4 ) 23 -OH, a polyether and aliphatic hydrocarbon chain surfactant) mixed surfactantsystem as the supramolecular structure directing agent (SDA) in the presence of tartaric acid(TA) as a mineralizer of Ti(IV). XRD, N2 adsorption and TEM data suggested the presence ofmesophase with hexagonal pore arrangements and the UVvisible, FT IR and XPS studies suggestedthe incorporation of mostly tetrahedral titanium (IV) species in the highly ordered silica network.This mesoporous titanium silicate material showed excellent catalytic activity and selectivity in theepoxidation of styrene using dilute aqueous H 2 O 2 as oxidant.M Mukherjee, Debraj Chandra†, Nawal Kishor Mal†, Asim Bhaumik†SP5.1.2.4 Nitrogen mediated interaction in polyacrylamide-silver nanocompositesPolyacrylamide (PAM)-silver nanocomposite materials have been synthesized by reduction of silversalt in polyacrylamide matrix. Silver nanoparticles embedded in the polymer matrix, observedthrough TEM, suggests attractive polymer-particle interaction. Detailed spectroscopic investigationshave been carried out on the nanocomposite samples using a range of techniques to understandthe nature of the interaction. The XPS core level spectra and FTIR results indicate that the nanoparticlesare attached to the pendant group of the polymer through physical interactions. XPSValence band study confirms that the interaction between the polymer and the silver nanoparticlesoccur through partial charge transfer from the metal particles to the nitrogen sites of the polymerside chains. The modifications associated with the silver nanoparticles are mainly due to confinementeffects.Subhrangsu Mukherjee, M MukherjeeSP5.1.2.5 Effect of solvent-polymer interaction in swelling dynamics of ultra-thin polyacrylamidefilms: A neutron and X-ray reflectivity studyThe swelling dynamics of the ultra-thin polyacrylamide (PAM) spin-coated films in saturatedvapour of D 2 O and H 2 O were studied using neutron and X-ray reflectivity. A uniform scatteringlength density (SLD) profile represents the dry PAM films, whereas the SLD profiles correspondingto the swelled films were characterized with a decreasing solvent concentration along the filmthickness from top surface to the film/substrate interface. The diffusion mechanism of D 2 O intothe films was found to be a non-Fickian process, as the D 2 O diffusion coefficient was observed to bedecreasing as a function of film thickness. The thickness dependent structural changes in the drypolymer films were suggested from the increased density of thinner films. The diffusion coefficientof polymer chains in the solvent on the contrary was independent of film thickness. A different