Thermo-Reversible Cellulose Micro Phase-Separation in Mixtures of Methyltributylphosphonium Acetate and γ-Valerolactone or DMSO.
Chemphyschem
; 23(7): e202100635, 2022 04 05.
Article
in En
| MEDLINE
| ID: mdl-35130371
ABSTRACT
We have identified cellulose solvents, comprised of binary mixtures of molecular solvents and ionic liquids that rapidly dissolve cellulose to high concentration and show upper-critical solution temperature (UCST)-like thermodynamic behaviour - upon cooling and micro phase-separation to roughly spherical microparticle particle-gel mixtures. This is a result of an entropy-dominant process, controllable by changing temperature, with an overall exothermic regeneration step. However, the initial dissolution of cellulose in this system, from the majority cellulose I allomorph upon increasing temperature, is also exothermic. The mixtures essentially act as 'thermo-switchable' gels. Upon initial dissolution and cooling, micro-scaled spherical particles are formed, the formation onset and size of which are dependent on the presence of traces of water. Wide-angle X-ray scattering (WAXS) and 13 C cross-polarisation magic-angle spinning (CP-MAS) NMR spectroscopy have identified that the cellulose micro phase-separates with no remaining cellulose I allomorph and eventually forms a proportion of the cellulose II allomorph after water washing and drying. The rheological properties of these solutions demonstrate the possibility of a new type of cellulose processing, whereby morphology can be influenced by changing temperature.
Key words
Full text:
1
Database:
MEDLINE
Main subject:
Cellulose
/
Ionic Liquids
Language:
En
Journal:
Chemphyschem
Journal subject:
BIOFISICA
/
QUIMICA
Year:
2022
Type:
Article
Affiliation country: