Laser- Induced Graft Copolymerization of Some Acrylic Acid Derivatives on Gum Arabic and Gum Karaya

Abstract

The grafting of Acrylamide (AAm) and 3,3-dimethyl acrylic acid on Gum Arabic and Gum Karaya, in aqueous medium initiated by ceric ammonium nitrate (CAN), has been studied in this work under a slow stream of nitrogen gas. The optimum conditions of monomer concentration, initiator concentration, polymerization temperature,reaction time and gums concentrations were studied in terms of percentage of graft efficiency (%GE) and percentage of graft yield (%GY). The optimum conditions obtained for grafting of acrylamide and 3,3-dimethyl acrylic acid on 0.5 g Gum Karaya and Gum Acacia Senegal and monomers concentrations (acrylamide) and (3,3-dimethyl acrylic acid) were 0.02 mol dm-3, (CAN) = 0.91 x 10-3 mol dm-3, temperature = 30oC, in 100 ml distilled water and reaction time = 3 hours. Diode laser with wavelength of (532 nm) and power (200mW ) with exposure time 60 minutes was used as an initiator to produce 96.4%, 27%,90% and 36% as maximum %GY and %GE were obtained for GA-g-AAm and GA-g-3,3-dimethyl acrylic acid respectively. While 96.5%, 27.4%, 90% and 36% maximum %GY and %GE for GK-g-AAm and GK-g-3,3-dimethyl acrylic acid respectively. Grafted copolymers were characterized by FTIR, appearance of new peaks, and disappearance of others confirm grafting, From results of Thermogravimetric Analysis (TGA) we observed that the graft copolymers were more thermally stable than the original gums, study of X-ray diffraction (XRD) showed that the graft copolymers more crystal than gums, and the surface topography of the graft copolymers were studied by Scanning Electron Microscope (SEM) and compared with the gums. The exterior surface of graft copolymers appears different from the parent’s gums. Hence, the surfaces evidence the supports grafting of monomers in gums.