Kunj Behari

Graft copolymerization of acrylamide onto xanthan gum

Abstract The graft copolymerization of acrylamide onto xanthan gum initiated by the Fe 2+ /BrO 3 − redox system in aqueous medium was studied gravimetrically under a nitrogen atmosphere. The effect of Fe 2+ , BrO 3 − , H + , acrylamide and xanthan gum on graft copolymerization was studied by determining the grafting parameters, i.e. grafting ratio, efficiency, conversion and add on. Homopolymer too has been separated out. An increase in grafting parameters was observed with increase in ferrous ion concentration (4×10 −3 mol dm −3 to 5.0×10 −3 mol dm −3 ) while with increasing bromate ion concentration, grafting ratio, efficiency, add on and conversion were found to decrease. It was observed that grafting takes place efficiently when acrylamide concentration and temperature were 4.0×10 −3 mol dm −3 and 35°C, respectively.

Synthesis and microstructural characterization of low-molar-mass poly(vinylidene fluoride)

Abstract The kinetic features of vinylidene fluoride (VDF) radical polymerization in solution, initiated by bis(4-butylcyclohexyl)peroxydicarbonate, have been investigated in three different solvents (acetone, ethyl acetate and methyl acetate) under homogeneous conditions. Many significant deviations of the dependence of the polymerization rate on the ‘ideal’ 1.0 and 0.5 exponent values of monomer and initiator concentrations, respectively, are indicative of anomalous kinetic behaviours linked to concurrent reactions, which are operative during such polymerization. The complexity of the kinetic behaviour prevents, inter alia , the correct evaluation of chain transfer constants to the solvents from kinetic data. 19 F nuclear magnetic resonance spectroscopy has been used in order to get full microstructural characterization of the low-molar-mass poly(vinylidene fluoride) (PVDF) synthesized under the above conditions. Both chain transfer constants to the solvent and extent of chain inversions in PVDF have been evaluated by this technique.

Graft copolymerization of acrylic acid onto guar gum

The graft copolymerization of acrylic acid (AA) onto guar gum (GOH) was carried out by a peroxydiphosphate (PDP)–silver(I) system. Grafting ratio, efficiency, add-on, and conversion increase upon increasing the concentration of PDP and acrylic acid, whereas they decrease upon increasing the concentration of guar gum. Upon increasing the concentration of silver and hydrogen ions up to 2.0 × 10−3 and 4.87 × 10−2 mol dm−3, respectively, the grafting ratio and efficiency increase but decrease upon further increasing the concentration. The increase in temperature from 30 to 45°C increases the grafting ratio but the conversion efficiency decreases. The optimum time period for graft copolymerization was found to be 2 h. The graft copolymers were characterized by infrared spectroscopy and thermogravimetric analysis.

Graft Copolymerization of Methacrylamide onto Guar Gum Using a Potassium Chromate/Malonic Acid Redox Pair

The effect of reaction conditions on the grafting parameters during the grafting of methacrylamide (MAM) onto guar-gum (GOH) using potassium chromate/ malonic acid redox pair was studied under ni sphere at different temperatures. On increasing the chromate ion concentration (from 3.5 × 10 -3 mol.dm -3 to 20.0 × 10 -3 mol.dm -3 ) grafting parameters were found to increase. Grafting ratio, efficiency, and add on were found to increase with the increase in malonic acid concentration from 3.5 × 10 -3 mol.dm -3 to 10.0 × 10 -3 mol dm -3 . It was observed that maximum efficiency was obtained when the monomer concentration was 20.0 × 10 -3 mol.dm -3 . With increasing hydrogen ion concentration, grafting parameters were found to increase. Homopolymer concentration, however, was found to decrease with increasing hydrogen ion concentration. Optimum tempera time for grafting of MAM onto guar gum were found to be 35°C and 120 min respectively. The graft copolymer was characterized by IR spectroscopy and thermogravimetric analysis.

Synthesis and properties of a water soluble graft (chitosan-g-2-acrylamidoglycolic acid) copolymer.

The present paper reports the graft copolymerization of 2-acrylamidoglycolic acid onto chitosan by using potassium bromate/silver nitrate as an efficient redox initiator in an inert atmosphere. The effect of reaction conditions on grafting parameters i.e. grafting ratio, efficiency, conversion, add on, homopolymer and rate of grafting has been studied. Experimental results show that maximum grafting has been obtained at 0.4 g dm(-3) concentration of chitosan, 8.0×10(-2) mol dm(-3) concentration of 2-acrylamidoglycolic acid and 1.0×10(-3) mol dm(-3) concentration of hydrogen ion. It has also been observed that grafting ratio, add on, conversion, efficiency and rate of grafting increase up to 3.2×10(-3) mol dm(-3) of silver nitrate and 1.7×10(-2) mol dm(-3) of potassium bromate. Time (120 min) and temperature (40°C) were kept constant during reaction. The physicochemical properties of graft copolymer synthesized have been performed in terms of water swelling, metal ion sorption, flocculation and resistance to biodegradability with respect to the chitosan as a parent polymer. The graft copolymer has been characterized by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis.

Synthesis, characterization and applications of graft copolymer (κ-carrageenan-g-vinylsulfonic acid)

The synthesis of graft copolymer (κ-carrageenan-g-vinylsulfonic acid) is carried out in nitrogen atmosphere using potassium peroxymonosulfate (PMS) and malonic acid (MA) as redox system. The effect of reaction variables including the concentration of vinylsulfonic acid 1.3×10(-2) to 6.7×10(-2) mol dm(-3), PMS 4×10(-3) to 20×10(-3) mol dm(-3), MA 1.6×10(-3) to 4.8×10(-3) mol dm(-3), sulfuric acid 1×10(-3) to 8×10(-3) mol dm(-3), κ-carrageenan 0.4-1.8 g dm(-3) as well as time duration 60-180 min and temperature 25-45 °C has been studied. The water swelling capacity of graft copolymer is investigated. Flocculation property for both coking and non-coking coals is studied for the treatment of coal mine waste water. The graft copolymer has been characterized by FTIR and thermogravimetric analysis.

Kinetics of perphosphate-initiated polymerization of acrylamide with different activators

Abstract The kinetics of aqueous polymerization of acrylamide was studied under an inert atmosphere at 30 ± 1°C using perphosphate as initiator with different activators such as mercaptosuccinic acid and cysteine hydrochloride. The order with respect to perphosphate and acrylamide is found to be one-half and unity, respectively, in both redox systems. Mercaptosuccinic acid has half-order dependence on the rate of polymerization, whereas cysteine hydrochloride has first-order dependence. The overall energy of activation is 42.5 ± 2 kJ mol−1 and 38.3 ± 1 kJ mol−1 for perphosphate/mercaptosuccinic acid and perphosphate/cysteine hydrochloride redox systems, respectively. Polyacrylamide samples collected under different kinetic conditions are used for the determination of the intrinsic viscosity.

Studies of graft copolymerization of acrylamide onto guar gum using peroxydiphosphate–metabisulphite redox pair

The effect of reaction conditions on the grafting parameter during grafting of acrylamide onto guar gum has been studied using peroxydiphosphate–metabisulphite redox pair at 35 °C. Grafting ratio, efficiency and add-on all increase as the concentrations of peroxydiphosphate and acrylamide increase up to 40.0 × 10−3 mol dm−3 and 40.0 × 10−2 mol dm−3, respectively. It has been observed that the optimum concentrations of metabisulphite and guar gum for obtaining high grafting ratio, efficiency, add-on and conversion are 6.0 × 10−3mol dm−3 and 91.7 × 10−2 g dm−3, respectively. © 2000 Society of Chemical Industry

Cu+2/mandelic acid redox pair initiated graft copolymerization acrylamide onto guar gum

The effect of reaction conditions on the grafting parameters during the grafting of acrylamide (ACM) onto guar gum (GOH) by using a Cu +2 -mandelic acid (MA) redox couple was studied. On increasing the Cu +2 ion concentration (0.5 × 10 -2 to 1.0 × 10 -2 mol dm -3 ), an increase in total conversion of monomer, grafting ratio, efficiency, and add on was observed. Grafting ratios increased with an increase in concentration of mandelic acid and reaches its maximum value at 0.8 × 10 -2 mol dm 3 . It was observed that grafting onto guar gum takes place efficiently when monomer and hydrogen ion concentrations are 20.0 × 10 -2 and 2.2 × 10 -2 mol dm -3 , respectively. Optimum temperature and time for obtaining a maximum grafting ratio and efficiency was found to be 35 ± 0.2°C and 2 h, respectively. The plausible mechanism of grafting was suggested. The graft copolymer was characterized by infrared spectroscopy and thermogravimetric analysis.

Cerium(IV)-sorbose-initiated polymerization of acrylamide and methacrylamide

Abstract The kinetics of the aqueous polymerizations of acrylamide and methacrylamide employing the cerium(IV) ammonium nitrate-sorbose redox pair under an inert atmosphere were studied. It was found that the rate of monomer disappearance is directly proportional to the concentration of sorbose and inversely proportional to the cerium(IV) ion concentration but depends on the square of the monomer concentration. The rate of cerium(IV) ion disappearance is directly proportional to the initial concentration of cerium(IV) ion and sorbose but independent of the monomer concentration. The effects of various additives, namely alcohols, inorganic salts and so on, on the rates of polymerization of acrylamide and methacrylamide were also studied. The viscometric average molecular weight M v decreases on increasing the concentration of monomer and sorbose. A plausible mechanism based on experimental results is proposed.