G. Panda

Grafting Vinyl Monomers onto Silk Fibers. XIII. Graft Copolymerization of Methyl Methacrylate onto Silk Using Fe3+−Cysteine Redox System

Abstract The graft copolymerization of methyl methacrylate onto silk fibers initiated by the ferric chloride-eysteine redox system has been investigated in aqueous medium. The rate of grafting was calculated by varying the concentrations of monomer, initiator, acidity of the medium, cysteine, and temperature. The percentage of grafting increases with an increase of Fe3+ concentration up to 2,5 × 10−3 mol/L and thereafter it decreases. The graft yield increases steadily upon increasing the monomer concentration. The graft yield also increases with increasing cysteine concentration up to 0.5 × 10−3 mol/L and then decreases. The effect of the perchloric acid concentration, temperature, solvents, and certain neutral salts on graft yield has also been investigated and a suitable reaction scheme has been proposed.

Polymerization of Acrylonitrile: Kinetics of the Reaction Initiated by the Redox System Mn3/Mannitol

Abstract Polymerization of acrylonitrile initiated by the redox system Mn3+/mannitol has been investigated in aqueous sulfuric acid in the temperature range 35–50°C. The rate of polymerization Rp and the rate of disappearance of Mn+3 (−RM) were measured. The effect of certain water-miscible organic solvents, inorganic salts and complexing agents on the rate of polymerization have been investigated. Based on the experimental results, a suitable reaction mechanism is suggested involving the formation of complex between Mn3+ and the hydroxyl group of the substrate molecule, whose decomposition yields the initiating free radical; the polymer chain is terminated by the mutual combination of growing chains.

Polymerization of Acrylonitrile: Kinetics of the Reaction Initiated by the Mn3+/Glucose Redox System

Abstract The vinyl polymerization of acrylonitrile initiated by the redox system Mn3+-glucose has been studied in aqueous sulfuric acid at 30–50°C. The rate of polymerization, the rate of Mn3+ disappearance, etc. were measured. The effect of certain water miscible organic solvents, inorganic salts, dyes, solvent composition, solid substances, and inhibitors on the rate of polymerization has been investigated. Based on the experimental results, a suitable reaction mechanism involving the formation of a complex between Mn3+ and the substrate molecule, whose decomposition yields the initiating free radical with the polymer chain being terminated by the mutual combination of growing chains, has been suggested.

Effect of Phenols on the Acidic Permanganate/Thioglycerol Couple Initiated Polymerization of Methyl Acrylate

Abstract The effect of various phenols on the polymerization of methyl acrylate (MA) initiated by the acidic permanganate/thioglycerol redox couple has been studied in aqueous solution at 30°C. It was found that among the various phenols used, o-cresol, m-cresol, resorcinol, and quinol behave as very weak inhibitors but retard the reaction to a significant extent. Other phenols such as phenol, o-nitrophenol, p-nitrophenol, α-naththol, β-naphthol, catechol, and pyrogallol behave both as inhibitors, and retarders. The rate of this process is dependent upon the substituents in the phenol and often their position. However, it is noticed that all phenols, irrespective of their low or high values of transfer constants, retard the rate of polymerization. The polymerization reaction has also been studied at 25–40°C in the absence of phenols by varying the concentrations of other components. The rate of polymerization increases with increases in the concentration of the monomer and reducing agent, and with the cat...

Polymerization of Acrylonitrile Initiated by the Mn(III)/Ethane Thiol Redox System

Abstract Kinetics of vinyl polymerization of acrylonitrile initiated by the redox system Mn(III)/ethane thiol were investigated in aqueous sulfuric acid in the temperature range of 30-45°C. The rate of polymerization, rate of manganic ion disappearance, etc. were measured. The effect of certain water-miscible organic solvents, neutral electrolytes, and organic nitrogen compounds on the rate has been investigated. A mechanism involving the formation of a complex between Mn(III) and the thiol, whose decomposition yields the initiating free radical with the polymerization being terminated by mutual combination of the growing radicals, has been suggested.

Grafting Vinyl Monomers onto Silk Fibers. XI. Graft Copolymerization of Methyl Methacrylate onto Silk Using Fe3+-Thiourea Redox System

Abstract The graft copolymerization of methyl methacrylate onto silk fibers initiated by the ferric chloride-thiourea redox system has been investigated in aqueous medium. The rate of grafting was calculated by varying the concentrations of monomer, initiator, and thiourea, the acidity of the medium, and the temperature. The rate of grafting increases significantly with an increase of [FeCl3] up to 1.25 × 10−3 M and thereafter it slows down. The rate of grafting also increases with an increase of [thiourea] and [HClO4] up to 2.5 × 10−3 and 23.325 × 10−1 M, respectively, and thereafter it decreases. The graft percezage increases with an increase of the monomer concentration. The effect of some inorganic salts, solvents, and surfactants on the rate of grafting has also been investigated.

Grafting Vinyl Monomers onto Wool Fibers. VI. Graft Copolymerization of Methyl Methacrylate onto Wool Using Tetravalent Manganese-Oxalic Acid Redox System

Abstract Graft copolymerization of methyl methacrylate onto wool induced by the permanganate-oxalic acid redox system was investigated in aqueous medium. The rate of grafting was determined by varying the concentrations of monomer, oxalic acid, permanganate, acidity of the medium, temperature, and the reaction medium. The graft yield increases significantly with increasing oxalic acid concentration up to 1.5 × 10−-2 M and thereafter it decreases. The graft yield also increases wTth an increase of the monomer concentration, initiator concentration, acid concentration, and temperature up to a certain range and then decreases. The effect of some inorganic salts and surfactants on the rate of grafting has also been investigated and a suitable reaction mechanism has been proposed.

Tetravalent Cerium/Thioglycerol Couple Initiated Polymerization of Methyl Methacrylate

Abstract The kinetics of vinyl polymerization of methyl methacrylate initiated by the Ce(IV)/thioglycerol couple were investigated in an aqueous system in the temperature range 5–20°C. The rate of polymerization, the rate of Ce(IV) disappearance, etc. were measured at various concentrations of the monomer, thioglycerol (TG), and eerie ion. The effect of some electrolytes and organic nitrogen compounds, presumed to behave as ideal retarders or inhibitors, has been investigated. The proposed reaction scheme involves initiation by an organic free radical produced by direct interaction of Ce(IV) with the activator (TG) and termination by Ce(IV). Various rate parameters have been evaluated.