Microwave promoted synthesis of chitosan-graft-poly(acrylonitrile)

Using microwave (MW) irradiation, polyacrylonitrile was grafted onto chitosan with 170% grafting yield under homogeneous conditions in 1.5 min in the bsence of any radical initiator or catalyst. Under similar conditions a maximum grafting of 105% could be achieved when the K2S2O8/ascorbic acid redox system was used as radical initiator in a thermostatic water bath at 35 +/- 2degreesC. The representative graft copolymer was characterized by Fourier transform infrared spectra, thermogravimetric analysis, and X-ray diffraction measurement, taking chitosan as a reference. The effects of such reaction variables as monomer/ chitosan concentration, MW power, and exposure time on the graft co polymerization were studied. A probable mechanism for grafting without the redox system under microwaves was proposed. (C) 2004 Wiley Periodicals, Inc.