Abstract
A novel method has been developed to modify the natural polymer chitosan. The process utilizes a monomer prepared by employing a Morita-Baylis-Hillman (MBH) reaction. Specifically, the vinyl monomer 2-[hydroxy(pyridin-3-yl)methyl]acrylonitrile (HPA) was synthesized using a high-yielding MBH reaction of acrylonitrile with pyridine-3-carboxaldehyde in the presence of 1,4-diazabicyclo[2.2.2]octane. Conversion of HPA to 2-cyano-1-(pyridin-3-yl)allyl acrylate (CPA) was then carried out by reaction of acryloyl chloride. The highly functionalized monomer CPA was grafted onto chitosan through a reaction in 2% acetic acid containing a persulfate and a sulfite (K2S2O8/Na2SO3) as redox promoter. An optimal grafting percentage of 123% is obtained when the grafting process is conducted at 60 degrees C for 4h employing a 1:0.5 ratio of K2S2O8 and Na2SO3 at a concentration of 2.5x10(-3)molL(-1). Chitosan-graft-poly[2-cyano-1-(pyridin-3-yl)allyl acrylate] graft copolymers, having various grafting percentages, were characterized using Fourier transform infrared, H-1 NMR and C-13 NMR spectroscopies, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. Finally, the results of studies probing the antimicrobial activities of the polymers against selected microorganisms show that the graft copolymers display higher growth inhibition activities against bacteria and fungi than does chitosan. (c) 2014 Society of Chemical Industry