Conversion of Cellulose I to Stable Cellulose III

Abstract

Cotton cellulose in fiber, yarn, or fabric form was converted from cellulose I to the cellulose III polymorph. Excellent conversion to III was obtained by immersing cotton (cellulose I) in liquid ammonia at room temperature, subjecting it to pressures from 689.5 to 11,721.5 kPa (100 to 1700 psi) while saturated with ammonia, and de-gassing the ammonia at either room temperature or elevated (about 140°C) temperatures. De-gassing at either temperature was equally effective. Complete conversion to III was obtained when cotton fibers from a never-dried cotton boll were dried with dime thoxypropane, treated with liquid ammonia at 140°C and at 11,721.5 kPa, and dried at or above the critical temperature (132.5°C). Crystalline cellulose III obtained under high pressures was stable to boiling water. After several hours in boiling water, there was only a slight indication of its conversion to IV. Complete conversion of III to IV was obtained by first subjecting III to anhydrous ethylenediamine and then to the aprotic polar solvent, dimethylformamide.