Synthesis path versus distribution of functional groups in cellulose ethers

Different ways for carboxymethylation of cellulose are discussed exemplary for cellulose ether synthesis in terms of the resulting structural features. The industrially applied slurry process yields polymers with statistic amounts of the four differently substituted repeating units glucose, mono-, di-, and tri-O-carboxymethylglucose. Surprisingly, the newly developed totally homogeneous carboxymethylation in the efficient cellulose solvent Ni[tris(2-aminoethyl)amine](OH)(2) gives exactly the same result. Thus, the polymer is evenly accessible during both reaction paths. In contrast the carboxymethylation starting from homogeneous solutions of cellulose in N,N-dimethyl acetamide/LiCl or solutions of reactive derivatives of cellulose in dimethyl sulfoxide (DMSO) yields polyelectrolytes with a nonstatistic content of the building units. This is achieved via an induced phase separation forming highly reactive microstructures.