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UV-radiation induced grafting of methyl methacrylate onto sodium salt of partially carboxymethylated psyllium has been carried out using ceric ammonium nitrate as a photoinitiator in an aqueous medium. The reaction variables including concentrations of initiator, nitric acid, monomer, and amount of the backbone as well as time and temperature have been varied for establishing the optimized reaction conditions for grafting. The influence of these reaction conditions on the grafting yields has been discussed. The overall activation energy of grafting has been calculated. The infrared spectroscopic, thermogravimetric analysis, and scanning electron microscopic techniques have been used for the characterization of graft copolymers.

ABSTRACT:The graft copolymerization of methyl methacrylate (MMA) onto sodium salt of partially carboxymethylated guar gum (Na-PCMGG; degree of substitution ϭ 0.497) with ceric ammonium nitrate as a redox initiator in an aqueous medium was studied. The optimized reaction conditions affording the maximum percentage of grafting of MMA onto Na-PCMGG were determined through the variation of the concentrations of nitric acid, ceric ammonium nitrate, MMA, and Na-PCMGG and of the temperature and time. The effects of these parameters on the grafting yields and the rates of polymerization, graft copolymerization, and homopolymerization were also studied, and the results were examined. The graft copolymer sample was characterized with IR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy.

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Polyacrylonitrile (PAN)-grafted sodium salt of partially carboxymethylated tamarind kernel powder (Na-PCMTKP-g-PAN, %G ¼ 413.76 and %GE ¼ 96.48) was prepared using the established optimal reaction conditions for ceric-initiated graft copolymerization of acrylonitrile onto Na-PCMTKP (DS ¼ 0.15) in a homogeneous medium. The graft copolymer was hydrolyzed by 0.7N KOH solution at 90-95 C to yield the superabsorbent hydrogel H-Na-PCMTKP-g-PAN. The nitrile groups of Na-PCMTKP-g-PAN were completely converted into a mixture of hydrophilic carboxamide and carboxylate groups during alkaline hydrolysis, followed by in situ crosslinking of the grafted PAN chains. The products were characterized spectroscopically and morphologically. The swelling behavior of the unreported superabsorbent hydrogel, H-Na-PCMTKP-g-PAN, was studied by carrying out its absorbency measurements in low-conductivity water, 0.15M salt (NaCl, CaCl 2 , and AlCl 3 ) solutions, and simulated urine (SU) at different timings. The swelling behavior of the hydrogel in different swelling media followed the second-order kinetics. The values of the various swelling characteristics were reported.