Some aspects of graft polymerization of vinyl monomers onto cellulose by use of tetravalent cerium. VI

Abstract

The state of cellulose as defined by its crystallinity, grinding, and average degree of polymerization (D.P.) highly influences the grafting yield. Grinding of cellulose with a Wiley mill results in decreased grafting, while grinding with a ball mill or treatment with ethylenediamine, both of which lead to decrystallization of cellulose, nearly inhibits the grafting reaction from taking place. On the other hand, decreased D.P. leads to increased grafting yield. The governing factor being attributed to the specific surface of the cellulose. Increased specific surface, as decreased D.P., brings about an increase in the active sites formed on the cellulose and hence an increase in the grafting yield. However, this occurs up to a limit beyond which further increase in the specific surface, respectively, the formed active sites, as grinding with a Wiley mill and decrystallization, brings about termination reactions through disproportionation and coupling of the exceedingly increased free radicals, and hence grafting is decreased or nearly inhibited. Drying of cellulose at 105°C resulted in decreased grafting yield. This was attributed to condensation of the cellulose structure. It has been also found that the grafting yield is influenced by the type and origin of cellulose whose reactivities differ for different monomers.