Homogenous synthesis of hydroxyethylcellulose in NaOH/urea aqueous solution.

Hydroxyethylcellulose (HEC) was synthesized by a fully homogenous method from cellulose in 7.5 wt.-% NaOH/11 wt.-% urea aqueous solutions under mild conditions. HEC samples were characterized with NMR, SEC-LLS, solubility, and viscosity measurements. The MS and DS values of the obtained HEC samples are in the range from 0.54 to 1.44 and 0.45 to 1.14, respectively, and the relative DS values at C-2 and C-6 hydroxyl groups are slightly higher than those at C-3 hydroxyl groups. HEC samples are soluble in water starting from a MS of 0.57 and DS of 0.49, which display high viscosity in aqueous solutions. Moreover, a NaOH/urea aqueous solution is a stable system for cellulose etherification. In this way, we could provide a simple, pollution-free, and homogeneous aqueous solution system for synthesizing cellulose ethers.