Phase separation in charge-stabilized colloidal dispersions

2007 ◽  
pp. 117-117
Author(s):  
J. P. Hansen
Keyword(s):  
Phase Separation ◽  
Colloidal Dispersions

Phase separation in model colloidal dispersions

1984 ◽  
Vol 80 (9) ◽  
pp. 2599 ◽  
Author(s):  
John Edwards ◽  
Douglas H. Everett ◽  
Timothy O'Sullivan ◽  
Irene Pangalou ◽  
Brian Vincent
Keyword(s):  
Phase Separation ◽  
Colloidal Dispersions

scholarly journals Aggregation by depletion attraction in cultures of bacteria producing exopolysaccharide

2012 ◽  
Vol 9 (77) ◽  
pp. 3490-3502 ◽  
Author(s):  
Gary Dorken ◽  
Gail P. Ferguson ◽  
Chris E. French ◽  
Wilson C. K. Poon
Keyword(s):  
Phase Separation ◽  
Growth Medium ◽  
Sinorhizobium Meliloti ◽  
Cell Concentration ◽  
Polymer Concentration ◽  
Colloidal Dispersions ◽  
Phase Behaviour ◽  
Self Organization ◽  
Form Part ◽  
Small Clusters

In bacteria, the production of exopolysaccharides—polysaccharides secreted by the cells into their growth medium—is integral to the formation of aggregates and biofilms. These exopolysaccharides often form part of a matrix that holds the cells together. Investigating the bacterium Sinorhizobium meliloti , we found that a mutant that overproduces the exopolysaccharide succinoglycan showed enhanced aggregation, resulting in phase separation of the cultures. However, the aggregates did not appear to be covered in polysaccharides. Succinoglycan purified from cultures was applied to different concentrations of cells, and observation of the phase behaviour showed that the limiting polymer concentration for aggregation and phase separation to occur decreased with increasing cell concentration, suggesting a ‘crowding mechanism’ was occurring. We suggest that, as found in colloidal dispersions, the presence of a non-adsorbing polymer in the form of the exopolysaccharide succinoglycan drives aggregation of S. meliloti by depletion attraction. This force leads to self-organization of the bacteria into small clusters of laterally aligned cells, and, furthermore, leads to aggregates clustering into biofilm-like structures on a surface.

Phase separation in colloidal dispersions with nonadsorbing polymer

1991 ◽  
Vol 269 (1) ◽  
pp. 28-35 ◽  
Author(s):  
D. Dey ◽  
C. S. Hirtzel
Keyword(s):  
Phase Separation ◽  
Colloidal Dispersions

scholarly journals Phase-Separation of Cellulose from Ionic Liquid upon Cooling: Preparation of Microsized Particles

2021 ◽  
Author(s):  
Jingwen Xia ◽  
Alistair W. T. King ◽  
Ilkka Kilpelainen ◽  
Vladimir Aseyev
Keyword(s):  
Ionic Liquid ◽  
Phase Separation ◽  
Electrolyte Solutions ◽  
Colloidal Dispersions ◽  
Fiber Spinning ◽  
Solution Temperature ◽  
Experimental Conditions ◽  
Critical Solution Temperature ◽  
Upper Critical Solution Temperature ◽  
Separation Temperature

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 (DMSO) or γ-valerolactone (GVL), 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.Regular micro-sized particles regenerated from a cellulose-OES mixture of tetrabutylphosphonium acetate:DMSO (70:30 w/w） upon cooling.

scholarly journals Phase-separation of cellulose from ionic liquid upon cooling: preparation of microsized particles

Cellulose ◽  
2021 ◽  
Author(s):  
Jingwen Xia ◽  
Alistair W. T. King ◽  
Ilkka Kilpeläinen ◽  
Vladimir Aseyev
Keyword(s):  
Ionic Liquid ◽  
Phase Separation ◽  
Electrolyte Solutions ◽  
Colloidal Dispersions ◽  
Fiber Spinning ◽  
Solution Temperature ◽  
Experimental Conditions ◽  
Critical Solution Temperature ◽  
Upper Critical Solution Temperature ◽  
Separation Temperature

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

Synthesis and phase separation during film formation of novel methyl methacrylate/n-butyl acrylate/methacrylic acid (MMA/BA/MAA) hybrid urethane/acrylate colloidal dispersions

Polymer ◽  
2004 ◽  
Vol 45 (18) ◽  
pp. 6235-6243 ◽  
Author(s):  
Daniel B. Otts ◽  
Sandipan Dutta ◽  
Ping Zhang ◽  
Oliver W. Smith ◽  
Shelby F. Thames ◽  
...  
Keyword(s):  
Phase Separation ◽  
Methyl Methacrylate ◽  
Methacrylic Acid ◽  
Butyl Acrylate ◽  
Film Formation ◽  
Colloidal Dispersions ◽  
Urethane Acrylate

Hierarchically Porous Oxides, Hybrids and Polymers via Sol-gel Accompanied by Phase Separation

2007 ◽  
Vol 1007 ◽  
Author(s):  
Kazuki Nakanishi
Keyword(s):  
Phase Separation ◽  
Sol Gel ◽  
Colloidal Dispersions ◽  
Solution Ph ◽  
Pure Alumina ◽  
Macroporous Silica ◽  
Phosphorylated Compounds ◽  
Hierarchical Porous ◽  
Porous Oxides ◽  
Pure Phases

ABSTRACTIn various crosslinking systems containing metal oxides, organo-siloxane polymers and pure hydrocarbons, monolithic materials with hierarchical well-defined macropores and controlled mesopores have been synthesized. Synthetic progress in alkoxy-derived macroporous silica lead to the preparation of long-range ordered mesoporous skeletons in well-defined macroporous framework. Alkylene-bridged silicon alkoxides can also be prepared into similarly hierarchical porous structures with broadened variations in framework morphology. Macro-mesoporous alkoxy-derived pure titania and zirconia have been prepared using hydrochloric acid – mediated processes. Compared with those prepared from colloidal dispersions, alkoxy-derived macroporous titania exhibited much higher mechanical strength. Titania monolith is a promising candidate as a separation medium to discriminate phosphorylated compounds in a liquid chromatography mode. Pure alumina macroporous monolith has been first synthesized from aluminum salt using propylene glycol as a proton scavenger to thrust the solution pH from acidic into neutral conditions. Alumina-based complex oxides such as garnets and spinels can also be prepared in pure phases. Polymerization and phase separation in organic crosslinker system was also controlled to obtain well-defined co-continuous macro-frameworks instead of those composed of aggregated particles. These examples demonstrate the versatility of using phase-separation in gelling systems to obtain well-defined macroporous structures.

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