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Using microwave (MW) irradiation, polyacrylonitrile was grafted onto chitosan with 170% grafting yield under homogeneous conditions in 1.5 min in the bsence of any radical initiator or catalyst. Under similar conditions a maximum grafting of 105% could be achieved when the K 2 S 2 O 8 /ascorbic acid redox system was used as radical initiator in a thermostatic water bath at 35 Ϯ 2°C. The representative graft copolymer was characterized by Fourier transform infrared spectra, thermogravimetric analysis, and X-ray diffraction measurement, taking chitosan as a reference. The effects of such reaction variables as monomer/ chitosan concentration, MW power, and exposure time on the graft co polymerization were studied. A probable mechanism for grafting without the redox system under microwaves was proposed.

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Using microwave (MW) irradiation grafting of polyacrylonitrile (PAN) onto guar gum in water was done without using any radical initiator or catalyst within a very short reaction time. The extent of grafting could be adjusted by controlling the reaction conditions and maximum percentage grafting (%G) of about 188% was obtained under optimum conditions in 1.66 min. The average molecular weight of the grafted PAN chains and water-retention power of the alkali hydrolyzed MW-grafted gums were also determined and compared with those of the conventionally synthesized (cs) graft copolymer. A representative MWgrafted copolymer, guar-g-polyacrylonitrile was characterized by IR, NMR, XRD, TGA, and elemental analysis. A plausible mechanism for the grafting under MW was proposed.

Plants of Ipomoea genus are widely distributed in India as wild vegetation and are reported source for the seed gums. Seed gums from Ipomoea dasysperma, Ipomoea hederacea, and Ipomoea palmata plants were grafted with polyacrylonitrile (PAN) using potassium persulfate/ascorbic acid redox initiator for modifying their properties for potential industrial applications. Under identical grafting conditions, the extent of the grafting was observed to be dependent on the galactose-to-mannose ratio and the degree of the branching in the galactomannans. Viscosity, gel formation, film formation, and the shelf life of the grafted gum solutions and water and saline retention capacity of the grafted seed gums were determined and compared with the parent gums. Water retention of the alkalie hydrolyzed grafted seed gums were also studied. Grafted gums were characterized using FTIR, NMR, and XRD analysis.

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