Green and efficient tool for grafting acrylonitrile onto starch nanoparticles using microwave irradiation

Abstract

In this study our previously prepared and fully characterized starch nanoparticles (SNPs) were graft copolymerize with acrylonitrile (AN) by microwave irradiation method without toxic chemical initiator. This was done to see the impact of microwave irradiation method as green and efficient tool with respect to reduction in organic solvents, toxic chemical initiator and exposer time on maximizing the graft yield % in comparison with other classical tools. The grafting parameters were expressed in terms of graft yield %. The latter was estimated gravimetrically (based on dry weight method) and titrimetrically (based on nitrogen %) to evaluate the best accurate standard metrological method for estimating the graft yield. The foremost factors affecting the grafting reaction were studied in terms of microwave power, acrylonitrile and starch nanoparticles concentration as well as contact time. The optimum reaction conditions were obtained when; starch nanoparticles, 1 g; acrylonitrile, 1.5 ml; microwave irradiation power, 500 W, reaction time 90 S were used. Starch nanoparticles and poly (AN)-starch nanoparticles graft copolymers were characterized by various analytical techniques. It was found from the obtained results that, Fourier transform infrared spectroscopy (FT-IR) analysis ascertains nitrile group attachment to starch nanoparticles chains. X-ray diffraction and scanning electron microscopy demonstrate an increased amorphous region of starch nanoparticles and grafted copolymers, while the thermo gravimetric analysis (TGA) emphasized the increase in thermal stability of the copolymers in comparison with starch nanoparticles counterparts. Tentative mechanisms, which demonstrate all occasions that happen during the whole course of the polymerization reaction, have been proffered.