Carboxymethylation of cellulose in unconventional media

Carboxymethylation of cellulose in the new and highly efficient aqueous solvent Ni(tren)(OH)(2), [tren=tris(2-aminoethyl)amine] and in melts of LiClO4 . 3H(2)O or N-methyl-morpholine-N-oxide (NMMNO), which is now widely applied for cellulose fibre production, was investigated. In case of Ni(tren)(OH)(2), a totally homogeneous carboxymethylation of cellulose with sodium monochloroacetate, in the presence of an aqueous NaOH solution is possible for the first time. Structure analysis by means of HPLC and H-1-NMR after chain degradation showed results comparable with findings for CMC obtained by the heterogeneous slurry process, that is, a statistic distribution of substituents along the polymer chain and functionalisation of the hydroxyl groups in the order C-6 greater than or equal to C-2 > C-3. The etherification of cellulose in a melt of LiClO4 . 3H(2)O, a new type of cellulose solvent, was shown to be possible and gave products of a statistic functionalisation pattern as well. In contrast, carboxymethylation starting from solutions of cellulose in NMMNO initiated with solid NaOH particles yields polymers with a nonstatistic distribution of functional groups along the chain, as observed for cellulose ethers prepared in reactive microstrctures starting from solutions of cellulose intermediates in dimethyl sulfoxide as well as of unmodified cellulose dissolved in N,N-dimethyl acetamide/LiCl.