NOPR Collection:

Photopolymerization of methyl methacrylate using dichloroacetic acid and dimethylaniline combination as photoinitiator

Sat, 01 Feb 1992 00:00:00 GMT

Title: Photopolymerization of methyl methacrylate using dichloroacetic acid and dimethylaniline combination as photoinitiator Authors: Ghosh, Premamoy; Mukherjee, Gauri Sankar Abstract: Photopolymerization of methyl methacrylate (MMA) in bulk and in solution at 40°C using dichloroacetic acid-dimethylaniline (DCAA-DMA) combination as photoinitiator has been studied kinetically. Initiator exponent and k/k_t values are ~ 0.27 and 1.30 x 10^-2 dm³^.mol^-1^.s^-1 respectively, while the monomer exponent is 1.0 in benzene and pyridine but < 1.0 in chloroform, carbon tetrachloride and eyelohexanone. End group analysis of the polymers prepared indicates that initiation of polymerization takes place by radicals derived from each initiating component on photo-decomposition of the complex between DCAA and DMA formed in situ. The radical generation process is dependent on the nature of the solvent used. The role of different solvents in modifying the initiation or radical generation process is analysed. The kinetic non-ideality in respect of low initiator exponent (< 0.5) is explained on the basis of significant initiator dependent termination through primary radicals or via degradative transfer to initiator. Page(s): 71-76

Studies on interaction of cationic dye with bacterial acidic polysaccharide

Sat, 01 Feb 1992 00:00:00 GMT

Title: Studies on interaction of cationic dye with bacterial acidic polysaccharide Authors: Mitra, A; Chakraborty, A K Abstract: Interaction of acidic capsular polysaccharide isolated from Klebsiella K17 with cationic dye pinacyanol chloride has been investigated by spectral measurements, and thermodynamic parameters of the interaction evaluated. The polymer induces metachromasy in the cationic dye and a blue-shift from 600 nm to 500 nm in the visible absorption spectrum of the dye is observed. The spectral changes have been studied during interaction of the dye cations with the polyanions at different polymer/dye molar ratios. The polyanion-dye compound is formed with polymer/dye stoichiometry of 1:1, indicating formation of stacking conformation. The values of thermodynamic constants, enthalpy of complex formation (Δ.H= - 7.02 kcalmol^-1), entropy change (ΔS= - 6.80 calmol^-1 deg^-1) and free energy change (ΔG at 307 K = - 4.98 kcalmo)^-1) indicate chromotropic character of the polymer in inducing metachromasy in the cationic dye pinacyanol chloride. Interaction of the polymer with acridine orange dye has also been studied by fluorescence measurements. Page(s): 77-82

Thionine-triethylamine interactions in mixed solvents

Sat, 01 Feb 1992 00:00:00 GMT

Title: Thionine-triethylamine interactions in mixed solvents Authors: Sidhu, K S; Singh, Satbir; Kumar, Anil Abstract: Addition of triethylamine (TEA) to thionine (Th⁺) solutions in CH₃CN /H₂O (9:1, v/v) and CH₃OH/H₂O (9:1, v/v) solvents leads to shift in absorption maxima from 597 nm to 500 nm and from 600 nm to 515 nm respectively. The spectral changes with various TEA concentrations have isosbestic points at 533 nm and 544 nm. Various types of interactions have been analysed to show that the charge transfer initiated redox disproportionation of the dye does not explain the observed data and the interaction in fact involves 1: 1 complexation of the lewis acid/base type with K = 2.60 X 10² mol^-1dm³ in CH₃CN/H₂O and 0.33 x 10² mol^-1dm³ in CH₃OH/H₂O solvent. Page(s): 83-85

Kinetics of hydrogen evolution reaction on bright platinum electrode in aqueous dimethylformamide solutions by cyclic voltammetry

Sat, 01 Feb 1992 00:00:00 GMT

Title: Kinetics of hydrogen evolution reaction on bright platinum electrode in aqueous dimethylformamide solutions by cyclic voltammetry Authors: Ray, Subrata K.; Datta, Jayati; Kundu, Kiron K Abstract: Kinetic behaviour of hydrogen evolution reaction (HER) has been studied on bright platinum electrode in aqueous mixtures of 0,25,50,75,90 and 100 wt% N,N-dimethylformamide (DMF) from both HCl and HClO₄ solutions by cyclicvoltammetry under varying sweep rates [500-1 mVs^-1] in the cathodic potential region of 0-1000 mV. The cyclic voltammograms are characterized by single cathodic and the corresponding anodic peaks and are found to be quasi-reversible in nature. The relevant kinetic parameters like the diffusion coefficient (D_R) of the reductant and the rate constant (k_s) (based on apparent area of the electrode) have been derived using the formulations of Shain and Nicholson. The values of D_R and k_s in aq. DMF mixtures decrease from that in pure water due to possible increased protophilicity of DMF-water mixtures which hinders the solvated H⁺ ions to approach the electrode surface for undergoing HER. Page(s): 86-90