Ceric(IV) ion-induced graft copolymerization of acrylamide and ethyl acrylate onto cellulose

Graft copolymerization of acrylamide (AAm) and ethyl acrylate (EA) onto cellulose has been carried out from their binary mixtures using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 25 +/- 1 degrees C. The extent of acrylamide grafting increased in the presence of the EA comonomer. The composition of the grafted chains (F-AAm = 0.52) was found to be constant during the feed molarity variation from 7.5 x 10(-2) to 60.0 x 10(-2) mol L-1, whereas the composition of the grafted chains (FAAm) was found to be dependent on feed composition (f(AAm)) and reaction temperature. The effects of ceric(IV) ion concentration, reaction time and temperature on the grafting parameters have been studied. The grafting parameters showed an increasing trend up to 6.0 x 10(-3) mol L-1 concentration of CAN at a feed molarity of 30.0 x 10(-2) mol L-1 and showed a decreasing trend on further increasing the concentration of CAN (> 6.0 x 10(-1) mol L-1) at a constant concentration of nitric acid (5.0 x 10(-2) mol L-1). The composition of the grafted chains (F-AAm) Was determined by IR spectroscopy and nitrogen content and the data obtained then used to determine the reactivity ratios of the acrylamide (r(1)) and ethyl acrylate (r(2)) comonomers by using a Mayo and Lewis plot. The reactivity ratios of acrylamide and ethyl acrylate were found to be r(1) = 0.54 and r(2) = 1.10, respectively, and hence the sequence lengths of acrylamide ((m) over bar M-1) and ethyl acrylate ((m) over bar M-2) in the grafted chains are arranged in an alternating form, as the product of the reactivity ratios of acrylamide and ethyl acrylate (r(1) x r(2)) is less than unity. The rate of graft copolymerization of the comonomers onto cellulose was found to be dependant on the 'squares' of the concentrations of the comonomers and on the 'square root' of the concentration of ceric ammonium nitrate. The energy of activation (Delta E-a) of graft copolymerzation was found to be S. 5 7 kJ mol(-1) within the temperature range from 15 to 50 degrees C. On the basis of the results, suitable reaction steps have been proposed for the graft copolymerzation of acrylamide and ethyl acrylate comonomers from their mixtures. (c) 2005 Society of Chemical Industry.