Dissolution of cellulose in ethylene diamine/salt solvent systems

Abstract

Investigation of the dissolution of cellulose in Ethylene Diamine (EDA)/Potassium thiocyanate (KSCN) solutions by infrared spectroscopy (FTIR) and thermal analysis (DSC) indicated that changes to the solvent during freeze thaw cycling of mixtures was consistent with increased interaction between cellulose and solvent. Thermal transitions in the system, however, occurred at temperatures outside the range used in thermal cycling to promote dissolution. Further exploration of the dissolution and mixing process indicated that mixing was the limiting step in solution formation. The dissolution of two types of cellulose with different molecular weights (Degree of Polymerization (DP)=210 and >1000) was studied using EDA/ KSCN solution as the solvent. The solubility and the dissolution rate of cellulose depended on both the solvent composition and cellulose molecular weight. Cellulose could dissolve faster in the solvent with lower salt concentration but the highest cellulose concentration was obtained in the solvent with 30$35% KSCN. Rheological measurements showed that cellulose solutions exhibited viscous solution behavior at low KSCN concentration but primarily elastic behavior at high salt concentration.

The role of salt on cellulose dissolution in ethylene diamine/salt solvent systems

“…-20°C (Frey et al 2006). A known weight of cellulose was then mixed with the solvent and kneaded in a sealed ziplock bag at ambient temperature.…”

“…Cellulose is biodegradable, renewable and abundant in nature, but very difficult to dissolve in common solvents due to considerable inter-and/or intra-molecular hydrogen bonding. Among the non-derivatizing solvents for cellulose are N-methyl morpholine-Noxide/water (NMMO/H 2 O) (Michael et al 2000), lithium chloride/dimethyl acetamide (LiCl/DMAc) (Striegel 2003), SO 2 -amine-dimethylsulfoxide (Isogai et al 1987), phosphoric acid/water (Boerstoel et al 2001), calcium thiocyanate/water (Ca(SCN) 2 / H 2 O) (Hattori et al 1998), NaOH/thiourea aqueous system (Cai and Zhang 2005), inorganic molten salts (Fischer et al 2000(Fischer et al , 2003, an ionic liquid solvent containing 1-butyl-3-methylimidazolium chloride (Swatloski et al 2002a, b), ammonia/ ammonium thiocyanate (NH 3 /NH 4 SCN) (Cuculo et al 1994a, b;Frey and Theil 2004), and ethylene diamine (EDA)/salt (Hattori et al 2004;Frey et al 2006). Many cellulose solvents include salt.…”

“…Analogs to the NH 3 /NH 4 SCN solvent system, the NH 2 NH 2 /thiocyanate salt system (Hattori et al 2002) and the EDA/salt system (Frey et al 2005(Frey et al , 2006 have been found to be able to dissolve cellulose. But NH 2 NH 2 is toxic and carcinogenic (Hattori et al 2004), which makes it a poor alternative.…”

Study of cellulose/ethylene diamine/salt systems

“…With the advance in NMR techniques, two dimensional NMR (2D NMR) and even three dimensional NMR (3D NMR) spectroscopy have increasingly been utilized in the molecular characterization of cellulose in that they permit an unambiguous assignment of signals (Homans 1990). FTIR (Infrared spectroscopy; Frey et al 2006), X-ray diffraction and scattering (Barry et al 1936;Davis et al 1943), light scattering (Roder et al 2001;Terbojevich et al 1985) and ESI-MS (electrospray ionization mass spectroscopy ;Striegel 2003) are also employed in the characterization of cellulose structure in various solvent systems. For instance, Frey et al (2006) noted the changes in hydrogen bonding between cellulose and EDA via FTIR, along with DSC (differential scanning calorimetry) studies.…”

“…FTIR (Infrared spectroscopy; Frey et al 2006), X-ray diffraction and scattering (Barry et al 1936;Davis et al 1943), light scattering (Roder et al 2001;Terbojevich et al 1985) and ESI-MS (electrospray ionization mass spectroscopy ;Striegel 2003) are also employed in the characterization of cellulose structure in various solvent systems. For instance, Frey et al (2006) noted the changes in hydrogen bonding between cellulose and EDA via FTIR, along with DSC (differential scanning calorimetry) studies. Chen et al (2006) studied the crystalline structure and morphology of regenerated cellulose fibers from the NaOH/thiourea aqueous solutions using WAXD (wide angle X-ray diffraction) and SAXS (small angle X-ray scattering).…”