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The graft copolymerization of acrylonitrile (AN) and ethyl acrylate (EA) comonomers onto cellulose has been carried out using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 35±0.1°C. The addition of ethyl acrylate as comonomer has shown a significant effect on overall and individual graft copolymerization of acrylonitrile on cellulose. The graft yield (%GY) and other grafting parameters viz. true grafting (%GT), graft conversion (%CG), cellulose number (Ng) and frequency of grafting (GF) were evaluated on varying the concentration of comonomers from 6.0–30.0×10−1 mol dm−3 and ceric (IV) ions concentration from 2.5–25×10−3 mol dm−3 at constant feed composition (fAN 0.6) and constant concentration of nitric acid (7.5×10−2 mol dm−3) in the reaction mixture. The graft yield (%GY) and other grafting parameters were optimal at 15×10−1 mol dm−3 concentration of comonomers and at 10×10−3 mol dm−3 concentration of ceric ammonium nitrate. The graft yield (%GY) and composition of grafted chains (FAN) was optimal at a feed composition (fAN) of 0.6. The energy of activation (Ea) for graft copolymerization has been found to be 16 kJ mol−1. The molecular weight (Mw) and molecular weight distribution (Mw/Mn) of grafted chains was determined by GPC and found to be optimum at 15×10−1 mol dm−3 concentration of comonomer in the reaction mixture. The composition of grafted chains (FAN) determined by IR method was used to calculate the reactivity ratios of monomers, which has been found to be 0.62 (r1) and 1.52 (r2), respectively for acrylonitrile (AN) and ethyl acrylate (EA) monomers used for graft copolymerization. The energy of activation for decomposition of cellulose and grafted cellulose was determining by using different models based on constant and different rate (β) of heating. Considering experimental observations, the reaction steps for graft copolymerization were proposed.
5 Acknowledgements
Authors are thankful to C.S.I.R., New Delhi, for financial assistance. The research facilities provided by I.I.T. Roorkee is thankfully acknowledged.