p-Toluenesulfonyl esters in cellulose modifications : acylation of remaining hydroxyl groups

New soluble cellulosics with interesting molecular structures and properties were obtained by the acylation of remaining hydroxyl groups of pure, homogeneously synthesized p-toluenesulfonylcelluloses of different degree of p-toluenesulfonyl (tosyl) substitution (DS Tosyl ) ranging from 0.5 to 2.0 in pyridine and sodium acetate as a catalyst with various aliphatic, aromatic and unsaturated carbonic acid anhydrides as well as isocyanates. The reactions proceed homogeneously and yield products of a high degree of acyl substitution (DS Acyl ). In the case of acetic and propionic acid anhydrides a complete functionalization of all free hydroxyl groups was achieved. Even with fatty acid anhydrides like stearic anhydride 94% of the remaining OH groups were acylated. The new polymers are readily soluble in common organic solvents such as acetone, dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, and tetrahydrofuran. They are solution processible film- and membrane-forming materials. Tosylcellulose phthalates and trimellitates of appropriate DS Tosyl and DS Acyl values are even soluble in aqueous NaOH. Compared to the original tosylcelluloses, the thermal degradation of tosylcellulose acylates was initiated at nearly the same temperature independent of type and degree of esterification providing an equal DS Tosyl . The stability found is sufficiently high for processing.