Phase behavior of the quasiternary system <i>N</i>‐methylmorpholine‐<i>N</i>‐oxide, water, and cellulose

Abstract

Abstract The crystallization and melting behavior of the system N ‐methylmorpholine‐ N ‐oxide (MMNO)–H 2 O–cellulose has been studied by differential scanning calorimetry, optical and electron microscopy, and x‐ray scattering. The phase diagram of the MMNO–H 2 O solvent system is reported up to a water content of 28% w/w. MMNO forms two crystalline hydrates, namely a monohydrate (13,3% w/w H 2 O) and a hydrate comprising five molecules of crystal water per two MMNO molecules (28% w/w H 2 O), which melts at 78°C and 39°C, respectively. The melting points of the various diluent crystals are strongly depressed in the presence of cellulose. For example, the solvent liquidus curve in the quasibinary system MMNO.1H 2 O–cellulose can be described very well using the simple Flory–Huggins expression with an interaction parameter χ = −3. Finally, the MMNO‐rich part of the melting point/composition diagram of the quasiternary MMNO–H 2 O–cellulose system is constructed and discussed.