Graft polymerization of some vinyl monomers onto alkali‐treated cellulose

Abstract

AbstractTreatment of cellulose by different concentrations of alkali, namely, 5–30% NaOH, changed its fine structure and transferred cellulose I into cellulose II. The decreased crystallinity due to alkali treatment and the transformation of cellulose I into cellulose II lowered the reactivity of cellulose toward the grafting polymerization reactions. Compactness of the structure as a result of the treatment of cellulose with 5% sodium hydroxide concentration decreased the rate of the grafting reaction and the grafting yield. On the other hand, such treatment of cellulose with different concentrations of alkali increased the rate of ceric consumption, i.e., increased the rate of oxidation of cellulose. Thus, the termination reaction of the grafting polymerization process may occur as a result of such oxidation and because of the increase of the active sites onto cellulose, leading to a decrease of the grafting yields and rate of grafting polymerization reaction by using the free‐radical grafting process. The use of the ionic‐xanthate method of grafting polyvinyl‐ and polyallyl‐on alkali‐treated cellulose shows an increase of grafting efficiency and grafting yields. Maximum grafting efficiency and yields were achieved when cellulose was treated with sodium hydroxide concentration below 15%, and maximum crystallinity indices were obtained. Using 15–25% sodium hydroxide lowered the indices of crystallinity, and lower grafting yields and grafting efficiency were achieved. Thus, transformation of cellulose I into cellulose II decreased the reactivity of these treated celluloses toward graft polymerization reactions by the use of the ionic‐xanthate method. In our opinion, termination reactions may also occur and affect the results.