Mahalingam Srinivasan

Bio: Mahalingam Srinivasan is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Condensation polymer & Diamine. The author has an hindex of 11, co-authored 53 publications receiving 357 citations.

Synthesis and properties of new polybenzimidazoles and N‐phenyl polybenzimidazoles with flexibilizing spacers on the polymer backbone

Abstract: Several new polybenzimidazoles (PBIs) and N-phenyl PBIs were synthesized by high temperature solution polycondensation techniques. Three different tetramine hydrochlorides and one N-phenyl tetramine hydrochloride were condensed independently with p-phenylenedioxydiacetic acid (PDDA), 2,2′-[isopropylidene bis(p-phenyleneoxy)] diacetic acid (bisacid A2) and 2,2′-[sulfonyl bis(p-phenyleneoxy)] diacetic acid (bisacid S) in polyphosphoric acid (PPA) at high temperatures. The polymers were obtained in 55–65% yield with inherent viscosities in the range 0.58–0.96 dL/g. Four model benzimidazoles (MBI) were also synthesized to confirm the formation of polybenzimidazoles. The PBIs and MBIs were characterized by infrared spectroscopy and elemental analysis. The properties of the polymers such as solubility, density, crystallinity, and thermal, thermoxidative, and isothermal stabilities were studied.

Studies on the hydrogenation of olefins using polymer-bound palladium (II) species

Abstract: bis-Benzonitriledichloropalladium(II) [(PhCN)2PdCl2] has been supported on two copolymers containing carboxyl and pyridyl groups and has been employed as a catalyst for the hydrogenation of olefins under mild conditions. The coordination environment and the nature of the metal species on the polymer have been studied by IR, ESCA, X-ray and a chemical test based on KCN treatment. Based on experimental evidence it is proposed that the polymer-palladium complexes initially contain palladium atoms with chlorine atom bridges which are cleaved in the activation. The catalysts were found to be active towards the hydrogenation of olefins under ambient conditions (room temperature and 1 atmosphere total pressure). The kinetic and mechanistic aspects of the hydrogenation of styrene and acrylonitrile and recycling capacity data using one catalyst (Cat-I) are reported.

The migration of plasticizer in solid propellant grains

Abstract: The migration of the plasticizer, dioctyl adipate (DOA) in the accelerated ageing of composite propellant has been studied. The method is based on the extraction of DOA with carbon tetrachloride and its estimation by gas chromatography. The concentration of DOA in the propellant at different distances from the insulation was determined after a definite ageing period and compared with the initial DOA concentration. The effect of (a) the ageing period, and (b) the ageing temperature on the degree of migration was examined. The present studies confirm the existence of plasticizer migration in the propellant adjacent to the insulation, during ageing.

Polyurethane types, synthesis and applications – a review

Abstract: Polyurethanes (PUs) are a class of versatile materials with great potential for use in different applications, especially based on their structure–property relationships. Their specific mechanical, physical, biological, and chemical properties are attracting significant research attention to tailoring PUs for use in different applications. Enhancement of the properties and performance of PU-based materials may be achieved through changes to the production process or the raw materials used in their fabrication or via the use of advanced characterization techniques. Clearly, modification of the raw materials and production process through proper methods can produce PUs that are suitable for varied specific applications. The present study aims to shed light on the chemistry, types, and synthesis of different kinds of PUs. Some of the important research studies relating to PUs, including their synthesis method, characterization techniques, and research findings, are comprehensively discussed. Herein, recent advances in new types of PUs and their synthesis for various applications are also presented. Furthermore, information is provided on the environmental friendliness of the PUs, with a specific emphasis on their recyclability and recoverability.

Swollen liquid-crystalline lamellar phase based on extended solid-like sheets

Abstract: Ordering particles at the nanometre length scale is a challenging and active research area in materials science. Several approaches have so far been developed, ranging from the manipulation of individual particles to the exploitation of self-assembly in colloids. Nanometre-scale ordering is well known to appear spontaneously when anisotropic organic moieties form liquid-crystalline phases; this behaviour is also observed for anisotropic mineral nanoparticles resulting in the formation of nematic, smectic and hexagonal mesophases. Here we describe a lyotropic liquid-crystalline lamellar phase comprising an aqueous dispersion of planar solid-like sheets in which all the atoms involved in a layer are covalently bonded. The spacing of these phosphatoantimonate single layers can be increased 100-fold, resulting in one-dimensional structures whose periodicity can be tuned from 1.5 to 225 nanometres. These highly organized materials can be mechanically or magnetically aligned over large pH and temperature ranges, and this property can be used to measure residual dipolar couplings for the structure determination of biomolecules by liquid-state NMR. We also expect that our approach will result in the discovery of other classes of mineral lyotropic lamellar phases.

Cannabinoid receptor ligands

Abstract: Compounds of Formula (I) and/or pharmaceutically acceptable salts, solvates or prodrugs thereof, or pharmaceutical compositions containing such compounds exhibit anti-inflammatory and immunomodulatory activity, and can be effective asCB2 receptor ligands in treating cancer and inflammatory, immunomodulatory or respiratory diseases or conditions.

'Microencapsulated' and related catalysts for organic chemistry and organic synthesis

Abstract: 2.6. Microencapsulated Cu(acac)2 [MC Cu(acac)2] 606 2.7. Microencapsulated Palladium [MC Pd] 607 2.8. Microencapsulated Methathesis Catalyst 609 3. Polymer Incarcerated Catalysts 611 3.1. Polymer Incarcerated Palladium [PI Pd] 611 3.2. Polymer-Micelle Incarcerated (PMI) Palladium 617 3.3. Polymer Incarcerated Ruthenium Catalyst 619 3.4. Polymer-Micelle Incarcerated Scandium Trifluoromethanesulfonate [PMI Sc(OTf)3] and Ruthenium Catalyst [PMI Ru] 621

Synthesis of Sulfonated Polybenzimidazoles from Functionalized Monomers: Preparation of Ionic Conducting Membranes

Abstract: In the present work, a new sulfonated tetraamine and the corresponding sulfonated polybenzimidazoles (sPBI) were synthesized. For the sake of determining the best polymerization conditions, a study involving model compounds was first performed. A strong acid medium was used as polymerization solvent, which allowed to obtain high molecular weight sPBI. A series of polymers with ion exchange capacity (IEC) ranging from 0 to 2.6 mequiv/g were synthesized using a non-sulfonated tetraamine as a comonomer. The chemical structure of those polymers was confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) as well as by titration. Thermogravimetric analysis (TGA) and viscosity measurement were performed as well. On the other hand, different architectures of the copolymers were prepared, i.e., random, sequenced copolymers, and blends of the homopolymers. The membranes prepared from the sPBI display low water uptake. The ionic conductivities measured in the hydrated state at room temper...