Role of Solvent Parameters\nin the Regeneration of\nCellulose from Ionic Liquid Solutions

Abstract

The ionic liquids 1-ethyl-3-methylimidazolium acetate\n[emim]­OAc, <i>N</i>,<i>N</i>,<i>N</i>,<i>N</i>-tetramethylguanidium propionate [TMGH]­EtCO₂, and <i>N</i>,<i>N</i>,<i>N</i>,<i>N</i>-tetramethylguanidium acetate [TMGH]­OAc, and the\ntraditional cellulose\nsolvent <i>N</i>-methylmorpholine <i>N</i>-oxide\nNMMO were characterized for their Kamlet–Taft (KT) values at\nseveral water contents and temperatures. For the ionic liquids and\nNMMO, thresholds of regeneration of cellulose solutions by water were\ndetermined using nephelometry and rheometry. Regeneration from wet\nIL was found to be asymmetric compared to dissolution into wet IL.\nKT parameters were found to remain almost constant at temperatures,\nbetween 20–100 °C, even at different water contents. Among\nthe KT parameters, the β value was found to change most drastically,\nwith an almost linear decrease upon addition of water. The ability\nof the mixtures to dissolve cellulose was best explained by the difference\nβ–α (net basicity), rather than β alone.\nRegeneration of cellulose starts at thresholds values of approximately\nβ < 0.8 (β–α < 0.35) and displayed\nfour phases.