Reversible crosslinking in cellulose. VI. Formation of sulfonium derivatives by the reaction of cellulose β-mercaptoethylaminocarboxylate with methyl iodide

Abstract

The reaction of methyl iodide with cellulose β-mercaptoethylaminocarboxylate (RDTC) made from cotton was investigated. The product was found to contain dimethyl sulfonium groups in addition to S-methyl groups, with accompanying hydrolytic cleavage of some of urethane linkages. The iodide counterions could be easily exchanged with hydroxide and chloride ions. The dyeabilty of RDTC and its sulfonium derivatives toward Direct Sky Blue A was studied. The equilibrium uptake of the dye by RDTC decreased with increasing sulfur content, while the uptake by the sulfonium derivatives was higher than that of control cotton and increased with increasing sulfonium content. The counterions did not affect the dyeability. The dye adsorbed onto the sulfonium derivatives was very fast against solvent extraction, and could be extracted only with Cadoxen containing 0.5% sodium hydroxide. The equilibrium uptake of the dye was much more than the amount calculated on basis of the 1 : 1 ionic bonding between the sulfonic acid group in the dye molecule and the sulfonium group in the modified cotton. The spatial effect in the dye–sulfonium bonding is discussed.