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101.
Thiophosphoryl fluoride and phosphoryl fluoride have been found to initiate the polymerisation of tetrahydrofuran. The living polymer formed has a high molecular weight of the order of a million and the density is found to be between 0.98 - 1.02 g/cc. A cationic mechanism for the polymerisation has been proposed. 相似文献
102.
The kinetics of polymerization of acrylonitrile initiated by V5+-thiourea or V5+-ethylene thiourea have been studied at 30, 35 and 40°C in nitrogen. The rates of polymerization and V5+ disappearance, and the chain lengths of polymers were measured. The kinetics are consistent with the formation of an intermediate complex between the thiol form of thiourea or ethylene thiourea and the oxidant decomposition of which leads to the initiating radical. The effects of certain organic solvents (water miscible) and salts on the rate of polymerization have been studied. A kinetic scheme has been proposed and the various rate and energy parameters evaluated. 相似文献
103.
The Preparation of Sulphur Tetrafluoride from the Elements at low Temperature in an Inert Solvent Pure sulphurtetrafluoride cna be prepared by the fluorination of elemental sulphur in CCl3F at ?78°C in high yields. 相似文献
104.
Sudhansu Bhusan Dash Nilambar Baral Nrusingha C. Pati Padma L. Nayak 《Journal of polymer science. Part A, Polymer chemistry》1982,20(9):2371-2379
The kinetics of the aqueous polymerization of methyl methacrylate initiated by potassium peroxydisulfate–citric acid catalyzed by silver ion was investigated in nitrogen atmosphere. The rate of polymerization is proportional to the square root of peroxydisulfate concentration. The initial rate increases with increasing citric acid concentration up to 15 × 10?3M, after which it decreases. The rate of polymerization also increases initially with monomer concentration and decreases at higher monomer concentration. The effects of temperature and the addition of some solvents and salts on the rate of polymerization have also been studied and a suitable kinetic scheme has been proposed for the reaction. 相似文献
105.
A method is described for the flotation and determination of Mo(VI) in water at ng/ml levels. Mo(VI) is preconcentrated and separated by adsorbing colloid flotation employing aluminium(III) hydroxide as collector and sodium lauryl sulphate as surfactant at pH 5.3 ± 0.1. The molybdenum content in the froth is estimated by using the catalytic wave of Mo(VI) in the presence of nitrate by charging current compensated d.c. polarography (CCCDCP) or differential pulse polarography (DPP). The effect of variables such as pH, ionic strength, concentration of collector and surfactant, time of stirring and gas flow-rate on the recovery of Mo by flotation is reported. The effects of various cations and anions on the flotation and determination of Mo are studied. This method is employed for the determination of molybdenum in natural fresh water samples. 相似文献
106.
107.
S. Padma V. Mahadevan M. Srinivasan 《Journal of polymer science. Part A, Polymer chemistry》1988,26(1):195-200
Polybenzoxazinones were prepared in two successive steps from methylene-4,4′-diaminodiphenyl-3,3′-dicarboxylic acid and azodicarbonyl chloride in 40–60% yield. These polymers were characterized by molecular weight and IR and NMR spectra. Their physical properties like solubility, viscosity, and thermal stability were also studied in detail. 相似文献
108.
Kurma Srimathi Dasari Gouthami Nukala Satheesh Kumar Ravula Sharada Kandukuri Padma Bandari Srinivas 《Russian Journal of General Chemistry》2022,92(7):1326-1332
Russian Journal of General Chemistry - A series of new quinoxaline-1,2,4-thiadiazoles amide hybrids has been synthesized and evaluated for their anti-proliferative activity on four different human... 相似文献
109.
5, 10, 15, 20-tetrakis-(4-chlorophenyl) porphyrin, H2TTPCl4, has been isolated as a new polymorph following the modified Adler’s method and its X-ray crystal structure solved. The new polymorph (I) crystallises in the monoclinic space group, P21/n with a?=?10.1574(5) Å, b?=?8.9827(4) Å, c?=?20.9350(8) Å, β?=?102.532(4)°, V?=?1864.62(15) Å3, Z?=?2. The previously found polymorph, prepared using Lindsay method was crystallised in monoclinic space group, P21/a with a?=?15.776 (13) Å, b?=?8.646 (3) Å, c?=?14.087 (5) Å, β?=?96.05 (5)°, V?=?1910.7 (3) Å3, Z?=?2. The main difference between the two polymorphs seems to be the different packing arrangement of molecules in their crystal lattices. The dramatic self aggregation property of new polymorph (I) has also been investigated. The investigation reveals that under certain conditions of solute concentration and pH of the media, the compound exhibits a strong tendency to exist in a prominent self aggregated state in head-to-tail type (j-aggregation) molecular alignment. The self association behaviour of (I) was confirmed by UV-Vis absorption spectra, performed in chloroform by varying concentrations and pH changes and 1H NMR spectra, performed in deuterated chloroform at varying concentrations and their results have been discussed in detail. 相似文献
110.