Polymers from renewable resources. II. A study in the radio chemical grafting of poly(styrene-alt-maleic anhydride) onto cellulose extracted from pine needles

A binary mixture of styrene and maleic anhydride has been graft copolymeriz ed onto cellulose extracted from Pinus roxburghii needles. The reaction was initiated with gamma rays in air by the simultaneous irradiation method. G raft copolymerization was studied under optimum conditions of total dose of radiation, amount of water, and molar concentration previously worked out for grafting styrene onto cellulose. Percentage of total conversion (Pg), g rafting efficiency (%), percentage of grafting (Pg), and rates of polymeriz ation (R-p), grafting (R-g), and homopolymerization (R-h) have been determi ned as a function of maleic anhydride concentration. The high degree of kin etic regularity and the linear dependence of the rate of polymerization on maleic anhydride concentration, along with the low and nearly constant rate of homopolymerization suggest that the monomers first form a complexomer w hich then polymerizes to form grafted chains with an alternating sequence. Grafting parameters and reaction rates achieve maximum values when the mola r ratio of styrene to maleic anhydride is 1 : 1. Further evidence for the a lternating monomer sequence is obtained from quantitatively evaluating the composition of the grafted chains from the FT-IR spectra, in which the rati o of anhydride absorbance to aromatic (C=C) absorbance for the stretching b ands assigned to the grafted monomers remained constant and independent of the feed ratio of maleic anhydride to styrene. Thermal behaviour of the gra ft copolymers revealed that all graft copolymers exhibit single stage decom position with characteristic transitions at 161-165 degrees C and 290-300 d egrees C. (C) 1999 John Wiley & Sons, Inc.