• Satya P Moulik

      Articles written in Journal of Chemical Sciences

    • Ternary mixtures of alkyltriphenylphosphonium bromides (C12TPB, C14TPB and C16TPB) in aqueous medium: their interfacial, bulk and fluorescence quenching behaviour

      Gargi Basu Ray Soumen Ghosh Satya P Moulik

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      The self-aggregation behaviour of ternary mixtures of alkyl (C$_{12}^-$, C$_{14}^-$ and C$_{16}^-$) triphenylphosphonium bromides was studied by conductometry and tensiometry. The pure surfactants showed two Critical Micellar Concentrations (CMCs) by conductometry, but their ternary mixtures produce single CMC both by conductometry and tensiometry. The CMC values determined were found to be lower than that obtained from Clint equation suggesting synergistic interaction among the monomers within the micelles. Their bulk properties, like fraction of counterions bound to the micelles and free energy of micellization were evaluated. Interfacial parameters, like surface excess, minimum head group area of monomer and free energy of adsorption were also assessed. Interfacial adsorption was found to be more spontaneous than micellization. The head group area per monomer in ternary systems was larger than pure systems due to stronger electrostatic repulsion among the charged head groups. The values of the packing parameters supported the pure as well as ternary micelles to be spherical. The TPB surfactants efficiently quenched pyrene fluorescence; the performances of the homologues in this respect were assessed.

    • Physicochemical studies on ion-pair amphiphiles: Solution and interfacial behaviour of systems derived from sodium dodecylsulfate and 𝑛-alkyltrimethylammonium bromide homologues

      Kajari Maiti Subhash C Bhattacharya Satya P Moulik Amiya K Panda

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      Bulk and interfacial properties of ion-pair amphiphiles (IPA), formed between sodium dodecylsulfate (SDS) and 𝑛-alkyltrimethylammonium bromide homologues (C$_n$TAB; 𝑛 = 10, 12, 14, 16, and 18), have been investigated. Different phases and aggregated states, formed in the ternary combinations of C$_n$TAB/SDS/H2O, have been identified and described. Equimolar mixture of IPAs in water yielded precipitates, in the form of coacervates. Aqueous solubility of isolated coacervates in presence and absence of additives like cholesterol and bile salts have been examined. The isolated coacervates have been characterized by 1H NMR, FTIR, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and polarization microscopic measurements. The coacervates have appeared in the shape of needle and complex flower-like aggregates. Surface pressure (𝜋)-area (A) isotherm of the coacervates at the air/water interface have been constructed and compared with the lipid 1,2-dipalmitoyl-$sn$-glycero-3-phosphocholine (DPPC). Morphologies of the IPA monolayers at different surface pressures have been also examined by epifluorescence microscopy. The compressed interfacial monolayers have produced spherical (both regular and irregular) and fern-leaf like domains.

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