Polymers from renewable resources: kinetics of 4-vinyl pyridine radiochemical grafting onto cellulose extracted from pine needles

In view of the marked thrust of research activities in the area of biodegradable polymers use of pine needles as renewable stock of polymeric materials has been made to synthesize graft copolymers for biomedical and industrial applications. 4-Vinyl pyridine (4-VP) has been radiochemically grafted onto cellulose extracted from pine needles using simultaneous irradiation method in limited aqueous medium. Optimum grafting conditions and kinetic parameters such as percent grafting, grafting efficiency, total conversion of monomer and rates of polymerization, homopolymerization and grafting have been evaluated as a function of total dose, monomer concentration and amount of water. It is observed that variation in both total dose and monomer concentration leads to inconsistent increase and decrease of the grafting parameters. However, rate of polymerization shows unsteady but regular increase with increasing monomer concentration and total dose radiation. While optimum amount of water is required for maximum percent grafting, addition of methanol on the other hand leads to regular decrease in percent grafting as a consequence of fall in the rate of grafting contrary to some earlier reported studies. Evidence of grafting has been based on the comparative studies of cellulose and grafted cellulose by infrared spectroscopy, elemental analysis and thermal analysis. Grafting enhances thermal stability of cellulose backbone. The trends in the results have been explained by kinetic interpretation and suitable mechanism for grafting has been proposed. (C) 2000 Elsevier Science Ltd. All rights reserved.