Temperature-responsive cellulose by ceric(IV) ion-initiated graft copolymerization of N-isopropylacrylamide.

Temperature-responsive cellulose has been obtained by graft copolymerization of N-isopropylacrylamide (NIPAAm) monomer using ceric ammonium nitrate (CAN) as initiator at 25.0 +/- 0.1 degrees C in acidic medium. Kinetic and grafting parameters were evaluated at different concentrations of NIPAAm ranging from 1.25 x 10(-3) to 12.5 x 10(-3) mol dm(-3) and varying concentrations of CAN from 1.5 x 10(-3) to 9.0 x 10(-3) mol dm(-3) at constant concentration of nitric acid (2.5 x 10(-2) mol dm(-3)). The graft copolymerization of NIPAAm onto cellulose has shown a significant increasing trend below lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAAm) and shown low energy of activation (18.0 kJ mol(-1)) for graft copolymerization within the temperature range of 10-35 degrees C as determined with Arrhenius plot. The PNIPAAm-grafted cellulose has shown improved thermal stability and shown temperature-dependent degree of swelling. Variation in degree of swelling of PNIPAAm-grafted cellulose as a function of temperature has been used to determine LCST of PNIPAAm-grafted cellulose. The contact angle (theta) has shown variation on increasing the graft yield and temperature. On the basis of experimental observations, the reaction steps for graft copolymerization have been proposed and a rate expression has been derived.

Graft copolymerization of ethyl acrylate onto cellulose using ceric ammonium nitrate as initiator in aqueous medium.

Ceric ammonium nitrate (CAN) in the presence of nitric acid has been used as efficient initiator for graft copolymerization of the ethyl acrylate onto cellulose at 35.0 +/- 0.1 degrees C. Graft copolymerization of ethyl acrylate onto cellulose has taken place through the radical initiation process. The graft yield and other grafting parameters have been evaluated by varying concentration of ethyl acrylate from 2.5 x 10(-1) to 15.0 x 10(-1) mol dm(-3) and ceric ammonium nitrate from 5.0 x 10(-3) to 25.0 x 10(-3) mol dm(-3) at constant concentration of the nitric acid (8.0 x 10(-2) mol dm(-3)). The rate of graft copolymerization has shown 1.5 order with respect to the concentration of the ceric ammonium nitrate. The graft copolymerization data obtained at different temperatures were used to calculate the energy of activation, which has been found to be 28.9 kJ mol(-1) within the temperature range from 20 to 50 degrees C. The effect of addition of cationic and anionic surfactants on graft copolymerization has also been studied. On the basis of the experimental observations, reaction steps have been proposed and a suitable rate expression for graft copolymerization has been derived.