Phase behavior of the quasiternary system N‐methylmorpholine‐N‐oxide, water, and cellulose

The crystallization and melting behavior of the system N‐methylmorpholine‐N‐oxide (MMNO)–H2O–cellulose has been studied by differential scanning calorimetry, optical and electron microscopy, and x‐ray scattering. The phase diagram of the MMNO–H2O 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 H2O) and a hydrate comprising five molecules of crystal water per two MMNO molecules (28% w/w H2O), 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.1H2O–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–H2O–cellulose system is constructed and discussed.