TY - JOUR
T1 - Phase-separation of cellulose from ionic liquid upon cooling
T2 - preparation of microsized particles
AU - Xia, Jingwen
AU - King, Alistair W.T.
AU - Kilpeläinen, Ilkka
AU - Aseyev, Vladimir
N1 - Funding Information:
Financial support of the Academy of Finland (Code: 310481) and Business Finland (Valcel) are gratefully acknowledged.
Publisher Copyright:
© 2021, The Author(s).
PY - 2021/11
Y1 - 2021/11
N2 - Abstract: Cellulose is an historical polymer, for which its processing possibilities have been limited by the absence of a melting point and insolubility in all non-derivatizing molecular solvents. More recently, ionic liquids (ILs) have been used for cellulose dissolution and regeneration, for example, in the development of textile fiber spinning processes. In some cases, organic electrolyte solutions (OESs), that are binary mixtures of an ionic liquid and a polar aprotic co-solvent, can show even better technical dissolution capacities for cellulose than the pure ILs. Herein we use OESs consisting of two tetraalkylphosphonium acetate ILs and dimethyl sulfoxide or γ-valerolactone, as co-solvents. Cellulose can be first dissolved in these OESs at 120 °C and then regenerated, upon cooling, leading to micro and macro phase-separation. This phenomenon much resembles the upper-critical solution temperature (UCST) type thermodynamic transition. This observed UCST-like behavior of these systems allows for the controlled regeneration of cellulose into colloidal dispersions of spherical microscale particles (spherulites), with highly ordered shape and size. While this phenomenon has been reported for other IL and NMMO-based systems, the mechanisms and phase-behavior have not been well defined. The particles are obtained below the phase-separation temperature as a result of controlled multi-molecular association. The regeneration process is a consequence of multi-parameter interdependence, where the polymer characteristics, OES composition, temperature, cooling rate and time all play their roles. The influence of the experimental conditions, cellulose concentration and the effect of time on regeneration of cellulose in the form of preferential gel or particles is discussed. Graphical abstract: Regular micro-sized particles regenerated from a cellulose-OES mixture of tetrabutylphosphonium acetate:DMSO (70:30 w/w) upon cooling[Figure not available: see fulltext.]
AB - Abstract: Cellulose is an historical polymer, for which its processing possibilities have been limited by the absence of a melting point and insolubility in all non-derivatizing molecular solvents. More recently, ionic liquids (ILs) have been used for cellulose dissolution and regeneration, for example, in the development of textile fiber spinning processes. In some cases, organic electrolyte solutions (OESs), that are binary mixtures of an ionic liquid and a polar aprotic co-solvent, can show even better technical dissolution capacities for cellulose than the pure ILs. Herein we use OESs consisting of two tetraalkylphosphonium acetate ILs and dimethyl sulfoxide or γ-valerolactone, as co-solvents. Cellulose can be first dissolved in these OESs at 120 °C and then regenerated, upon cooling, leading to micro and macro phase-separation. This phenomenon much resembles the upper-critical solution temperature (UCST) type thermodynamic transition. This observed UCST-like behavior of these systems allows for the controlled regeneration of cellulose into colloidal dispersions of spherical microscale particles (spherulites), with highly ordered shape and size. While this phenomenon has been reported for other IL and NMMO-based systems, the mechanisms and phase-behavior have not been well defined. The particles are obtained below the phase-separation temperature as a result of controlled multi-molecular association. The regeneration process is a consequence of multi-parameter interdependence, where the polymer characteristics, OES composition, temperature, cooling rate and time all play their roles. The influence of the experimental conditions, cellulose concentration and the effect of time on regeneration of cellulose in the form of preferential gel or particles is discussed. Graphical abstract: Regular micro-sized particles regenerated from a cellulose-OES mixture of tetrabutylphosphonium acetate:DMSO (70:30 w/w) upon cooling[Figure not available: see fulltext.]
KW - Cellulose regeneration
KW - Phosphonium acetate
KW - Spherulite
KW - UCST
UR - http://www.scopus.com/inward/record.url?scp=85116887691&partnerID=8YFLogxK
U2 - 10.1007/s10570-021-04230-w
DO - 10.1007/s10570-021-04230-w
M3 - Article
AN - SCOPUS:85116887691
SN - 0969-0239
VL - 28
SP - 10921
EP - 10938
JO - Cellulose
JF - Cellulose
IS - 17
ER -