The Effect of Alkyl Side Chain and Additives on the Anionic Polymerization of Isocyanates with Carbamate Group

The synthesis of new isocyanate monomers and their polymerization by anionic route is reported. Reaction of 1,6-diisocyanatohexane with aliphatic alcohols such as methanol, n-propanol and n-pentanol in 1:0.5 molar ratios was carried out in the presence of pyridine such that one  NCO group remained unreacted. The anionic polymerization of n-alkoxycarbonylaminohexyl isocyanates was carried out using sodium napthalenide (Na-Naph) initiator in the presence of 15-crown-5 (15C5) and sodium tetraphenylborate as the additives. While polymerization of n-propyloxycarbonylaminohexyl isocyanate (PAHI) and n-pentanoxycarbonylaminohexyl isocyanate (PEAHI) was feasible that of methoxycarbonylaminohexyl isocyanate (MAHI) led to an insoluble material. The polymers were isolated in high yields with NaBPh₄ as the additive.     

Tin Dioxide Nanowires: Evolution and Perspective of the Doped and Nondoped Systems

SnO₂ semiconductor nanowire is an extremely important technological material for use in nanophotonic and nanoelectronic devices. These semiconductor nanowires of desirable property can be achieved through a bottom-up approach to the controlled synthesis in a pure or doped state. Each of the synthetic methods offers materials with broad range structural, morphological, optical, and electrical properties. Selective doping of the SnO₂ nanowires by normal, transition or inner transition elements offer a broad variation in the optical and electrical properties and are open for further theoretical exploration of the properties as well as necessary changes possible for the improvement of the material properties. The properties of SnO₂ nanowires can be tuned either in the pure state by structural modification or doping during nanowire growth or after growth to meet most of the requirements.     

Two Homologous Intermetallic Phases in the Na-Au-Zn System with Sodium Bound in Unusual Paired Sites within 1D Tunnels

The Na-Au-Zn system contains the two intermetallic phases Na(0.97(4))Au(2)Zn(4) (I) and Na(0.72(4))Au(2)Zn(2) (II) that are commensurately and incommensurately modulated derivatives of K(0.37)Cd(2), respectively. Compound I crystallizes in tetragonal space group P4/mbm (No. 127), a = 7.986(1) ?, c = 7.971(1) ?, Z = 4, as a 1 × 1 × 3 superstructure derivative of K(0.37)Cd(2) (I4/mcm). Compound II is a weakly incommensurate derivative of K(0.37)Cd(2) with a modulation vector q = 0.189(1) along c. Its structure was solved in superspace group P4/mbm(00g)00ss, a = 7.8799(6) ?, c = 2.7326(4) ?, Z = 2, as well as its average structure in P4/mbm with the same lattice parameters.. The Au-Zn networks in both consist of layers of gold or zinc squares that are condensed antiprismatically along c ([Au(4/2)Zn(4)Zn(4)Au(4/2)] for I and [Au(4/2)Zn(4)Au(4/2)] for II) to define fairly uniform tunnels. The long-range cation dispositions in the tunnels are all clearly and rationally defined by electron density (Fourier) mapping. These show only close, somewhat diffuse, pairs of opposed, ≤50% occupied Na sites that are centered on (I) (shown) or between (II) the gold squares. Tight-binding electronic structure calculations via linear muffin-tin-orbital (LMTO) methods, assuming random occupancy of ≤ ～100% of nonpaired Na sites, again show that the major Hamilton bonding populations in both compounds arise from the polar heteroatomic Au-Zn interactions. Clear Na-Au (and lesser Na-Zn) bonding is also evident in the COHP functions. These two compounds are the only stable ternary phases in the (Cs,Rb,K,Na)-Au-Zn systems, emphasizing the special bonding and packing requirements in these sodium structures.     

Comparative Study on Energy Consumption and Yield by Various Thermal Plasma Routes for Production of Titania slag

In this paper, pre-reduced ilmenite concentrate of Indian region was processed successfully by thermal plasma routes to produce high titania slag. Effects of various parameters like time, yield and energy consumption, on TiO₂ and FeO content in the slag were studied. One of the main drawbacks of thermal plasma process is higher specific electrical power consumption, especially where power is costlier. So, the main focus is to reduce the energy consumption with better yield in various thermal plasma reactors. It is found that energy consumption decreases in respect to in-flight static bed plasma reactor. If the melting time kept within 2 min, the TiO₂ content and iron recovery increased, whereas melting time exceeds 2 min, low yield has been observed. At optimum conditions, TiO₂ content in the slag and the iron recovery are 84.5 and 80%, respectively. The phases before and after reduction, the sample were analyzed using X-ray diffraction.     

14CO2 labeling : a reliable technique for rapid measurement of total root exudation capacity and vascular sap flow in crop plants

Root release of organic compounds and rate of the vascular sap flow are important for understanding the nutrient and the source-sink dynamics in plants, however, their determination is procedurally cumbersome and time consuming. We report here a simple method involving ¹⁴C labeling for rapid and reliable measurement of root exudates and vascular sap flow rate in a variable groundnut population developed through seed gamma irradiation using a cobalt source (⁶⁰Co). An experimental hypothesis that a higher ¹⁴C level in the vascular sap would indicate a higher root release of carbon by the roots into the rhizosphere was verified.     

One‐Pot Fabrication of RGO–Ag3VO4 Nanocomposites by in situ Photoreduction using Different Sacrificial Agents: High Selectivity Toward Catechol Synthesis and Photodegradation Ability

Weak photon absorption and fast carrier kinetics in graphene restrict its applications in photosensitive reactions. Such restrictions/limitations can be overcome by covalent coupling of another photosensitive nanostructure to graphene, forming graphene‐semiconductor nanocomposites. Herein, we report one‐pot synthesis of RGO–Ag₃VO₄ nanocomposites using various sacrificial agents like ethanol, methanol, propanol and ethylene glycol (EG) under visible light illumination. The Raman spectral analysis and ¹³C MAS NMR suggest ethanol to be the best sacrificial agent among those studied. Thermal analysis studies, further, confirm the stability of the synthesized nanocomposite with ethanol as sacrificial agent. In view of this, the activity toward dye degradation was focused over the composites prepared via ethanol as sacrificial agent. It was observed and proved that cationic dyes could be degraded quantitatively and swiftly compared to anionic dyes (37.79%) in 1.5 h. This suggests that the surface of the nanocomposites is anionic as partial reduction takes place during synthesis process. In case of mixed dye degradation process, it was noticed that the presence of cationic dye doubles the degradation of anionic dye. The activity of these synthesized nanocomposites is more than five‐fold toward the phototransformation of phenol and photodegradation of textile dyes under visible light illumination.     

Grafting Vinyl Monomers onto Silk Fibers: Graft Copolymerization of Vinyl Monomers onto Silk Using the Vanadyl Acetylacetonate Complex

Abstract

The graft copolymerization of methyl methacrylate (MMA) onto mulberry silk fibers was studied in aqueous solution using the acetylacetonate oxovanadium (IV) complex. The rate of grafting was investigated by varying the concentration of the monomer and the complex, the acidity of the medium, the solvent composition of the reaction medium, the surfactants, and the inhibitors. The graft yield increases with increasing concentration of the initiator up to 8.75 × 10^?5 mol/L, of the monomer up to 0.5634 mol/L, and thereafter it decreases. Among the various vinyl monomers studied, MMA was found to be most suitable for grafting. Grafting increases with increasing concentration of HCIO₄ and with increasing temperature. Inhibitors like picryl chloride and hydroquinone significantly decrease the extent of grafting. Alcoholic solvents at a solvents/water ration of 10:90 seem to constitute the most favorable medium for grafting. A suitable reaction scheme has been proposed, and the activation energy calculated from the Arrhenius plots.     

Polymerization of Acrylonitrile: Kinetics of the Reaction Initiated by the Mn3+-Cyclohexanol Redox System

The vinyl polymerization of acrylonitrile initiated by the redox system Mn³⁺-cyclohexanol was investigated in aqueous sulfuric acid in the temperature range of 30–45° C. The rate of polymerization R_p and the rate of Mn³⁺ ion disappearance were measured. The effects of certain water-miscible organic solvents and certain anionic, cationic, and nonionic surfactants on the rate of polymerization were investigated. Based on the results obtained, a suitable reaction mechanism involving the formation of a complex between Mn³⁺ and the alcohol, whose decomposition yields the initiating free radical with the polymer chain being terminated by the mutual combination of growing chains is suggested.     

Pentavalent Vanadium-Ascorbic Acid Redox System Initiated Polymerization of Acrylonitrile

Kinetics of polymerization of acrylonitrile initiated by the redox system V⁵⁺ascorbic acid were investigated in aqueous sulfuric acid in the temperature range of 35–50°C, and the rates of polymerization, of V⁵⁺/disappearance, etc. were measured. From the result it was concluded that the polymerization reaction is initiated by an organic free radical arising from the V⁵⁺ - ascorbic acid complex formation followed by subsequent decomposition and terminated by V⁵⁺ions. A suitable kinetic scheme was proposed and the various rate parameters were evaluated.     

Aqueous Polymerization of Methyl Methacrylate Initiated by the Mn(lll)-Fructose Redox System

The kinetics of vinyl polymerization of methyl methacrylate initiated by the redox system Mn³-fructose were investigated in aqueous sulfuric acid in the temperature range of 20-25°C, and the rates of polymerization and disappearance of Mn³⁺ were measured. The effect of certain water-miscible organic solvents and certain cationic and anionic surfactants on the rate of polymerization has been investigated. A mechanism involving the formation of a complex between Mn³⁺ and fructose whose decomposition yields the initiating free radical with the polymerization being terminated by the metal ion has been suggested.