Preparation and characterization of some cellulose graft copolymers. Part III. The role of concurrent degradation during radiation grafting

Abstract

AbstractThe radiation degradation of cellulose acetate has been studied both in the dry state and in solution. The rate of degradation was greater in the solid state and was unaffected by oxygen. Conjugated solvents such as pyridine, toluene, and α‐methylstyrene were shown to exert considerable protection against the radiation degradation of cellulose acetate when in solution or as swollen films. α‐Methylstyrene has been used as a model for styrene to study the amount of degradation accompanying the grafting process. Matching experiments have been carried out by using both the mutual and the preirradiation methods of grafting. Considerably greater chain cleavage was found to accompany the grafting in the preirradiation case. With both methods the number of chain cleavages has been measured when α‐methylstyrene was present in the “grafting” solution and the number of grafted side chains when styrene was used. It was shown that at least twice as many grafted chains as cleavages occur with the mutual technique, but in the case of preirradiation the number of cleavages is comparable to the number of grafted chains. The G (grafted chain) value for cellulose acetate with styrene was determined and was about 1.1 in all cases. The G (chain cleavage) values varied, however, from 0.2 to 1.3, approximately. The proportion of grafted chains attached to the ester groups was determined by extraction with benzene after cold alkaline hydrolysis. About half of the grafts were found to be attached in each case, including the preirradiation product. In general, it can be said that in every case at least 50% of the graft copolymers are side‐chain grafts; this figure is probably considerably higher in the case of the mutual radiation preparations.