SYNOPSISSolubility of methyl cellulose (MC) depends on the degree of substitution (DS), the average degree of polymerization ( D P ) , and the distribution of methoxyl groups. Of these, the DS appears to be the most important. The DS of the MC depends on the conditions of preparation. The conditions studied in this work revealed that the DS of the MC increased as the concentration of sodium hydroxide increased from 10 to 50%. This result is attributed to the increase in the extent of formation of alkali cellulose I1 as a result of the increase in the alkali concentration and hence the increase of the DS of the MC. Decreasing both the ratio of dimethyl sulfate : cellulose and the liquor ratio increased the DS. High DS was achieved within a period of 2 and 3 h. However, the DS increased as the time increased. The decrease of the DS as the liquor ratio increased may be attributed to the sol-gel transition due to the interaction of the hydrophobic methoxyl groups within the polymer chains. To reveal the effect of the thermal sol-gel transition, the reaction was carried out in nonaqueous medium and the results obtained showed an increase of the DS with the increase of the solvent ratio until a maximum. This result may be contributed to the breakdown of the hydrogen bonding in the presence of solvents that transfer the reaction medium to the sol-form and hence more methylating reaction takes place. The degree of the solvation of the methyl groups into the solvents also plays a role.

Sodium bisulfite–soda lime glass has proved to be a good initiator for polymerization and graft polymerization onto cellulose of some vinyl monomers. A scheme dealing with the mechanism of initiation has been proposed assuming trapping of the bisulfite radical inside the glass frame‐work to form a so‐called sulfur‐impregnated solid. Such a solid has paramagnetic properties and acts on the vinyl monomers and cellulose as any free‐radical‐producing source thus leading to polymerization and graft polymerization onto cellulose. Other radicals containing sulfur, such as sulfite, sulfate, and persulfate failed to give such property with soda lime glass. With the sodium bisulfite–soda lime glass system the reactivity decreases in the order methyl methacrylate > ethyl acrylate > acrylonitrile which is inconsistent with the arrangement of acceptor monomers with decreasing electron‐donating ability. This may reflect interference of the addition reaction which may take place between the monomer and bisulfite and the rate of which may depend on the activation energy of the monomer.

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Beside the phenolic and quinone groups present in lignin which may affect retardation of the polymerization reactions of some vinyl monomers, the lignin network structure, the monomer configuration and the residual carbohydrate attached to lignin were found t o play an important role. Inhibierung und Retardation der Homopolymerisation von Vinylmonomeren durch LigninDie im Lignin vorhandenen Phenol-und Chinongruppen konnen bei einigen Vinylmonomeren eine Retardation der I'olymerisationsreaktion bewirken. Es wurde gefunden, daB daruberhinaus auch die Netzstruktur des Lignins, die Konfiguration der Monomere und der Kohlenwasserstoffrest am Lignin eine wesentliehe Rolle bei der Inhibierung spielen. klneubuposanue u pernapdayus eoaonoauwepuaayuu sunuawmx aonoaepos fiuenunoaMMeIolqlleCH B XllPHllHe @eHOJlbHhIe II XIIHOHbIe rpyIIIIbl MOrYT BbISblBaTb PeTapAa~llIO PeaKqMH IIOJIHMepll3aqHH y HeKOTOPbIX BHHHJIbHHX MOHOMePOB. HatgeHo, YTO KpOMe TOI'O E2 CeTllaTaFI CTpyKTypa JIlll'HHHa, KOH@HrJ'paqHR MOHOMepOB II yrJleBOAOpOAHbIm OCTaTOK y JIHI'HHHa IlPpaloT 3HaWITeJIbHyIo POJIb IIpH IlHfH6llpOBaHIIM.