Graft polymerization of some vinyl monomers onto alkali‐treated cellulose

Abstract

SYNOPSISTreatment of cellulose by different concentrations of alkali, namely, 5-30% NaOH, changed its fine structure and transferred cellulose I into cellulose 11. The decreased crystallinity due to alkali treatment and the transformation of cellulose I into cellulose I1 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 I1 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.

Grafting of methyl methacrylate (MMA) onto Antheraea assama silk fiber

“…The reaction system was intermittently stirred. After the desired reaction time, the silk fibers were taken out and washed thoroughly with boiling distilled water several times, and the homopolymer adhering to the silk fiber was removed by extraction with acetone at 35°C for 24 h 12, 20. The fibers were dried to a constant weight and kept in a desiccator over P 2 O 5 .…”

Preparation and biological characterization of cellulose graft copolymers

“…1(c) suggested that AA and AN have been successfully grafted onto the cellulose backbone. Factors affecting graft copolymerization and grafting amount including initiator concentration, monomer concentration, and reaction time have been well investigated [19][20][21] in Table 1 we report effect of temperature on grafting amount of AA and AN onto cellulose. High temperatures promote homopolymerization more than grafting.…”

Preparation and application of acrylonitrile‐grafted cyanoethyl cellulose for the removal of copper (II) ions

“…It can be noticed from the figure that the grafting yield (%) increased significantly with increase in the concentration of NaOH from 7.5% to 27.5% and the maximum grafting yield was obtained at the highest NaOH concentration (27.5%), regardless the DS of CE‐Cell. This result may be attributed to the possible increase in the number of xanthate groups at high NaOH concentration, which leads to more grafting yield 13. The grafting efficiency reached maximum at 12.5% NaOH concentration, then decreased again with increase in the concentration.…”

“…The ionic‐xanthate method of grafting can also be applied to graft vinyl monomers onto cellulosic materials 12–13. Grafting by this method is based on the introduction of a small number of xanthate groups into cellulose hydroxyls in the absence of any catalyst.…”