Particle-Induced Phase Separation in Quasi-Binary Polymer Solutions

Abstract

A long-ranged attractive force was recently detected between two mica plates immersed in a quasibinary polymer solution (Freyssingeas et al. Langmuir 1998, 14, 5877-5889). The quasi-binary polymer solution was aqueous ethyl(hydroxyethyl)cellulose (EHEC), where the EHEC had a broad polydispersity. The long-ranged attractive force in the EHEC solution could not be attributed to classical mechanisms such as depletion or bridging. In this study, we investigated if this attractive force can give rise to instability effects in mixed polymer-particle solutions. Accordingly, the effects of added particles on the phase behavior of aqueous EHEC solutions were investigated by cloud point measurements. Aqueous EHEC solutions phase separate on heating. Three different samples of EHEC were investigated, including hydrophobically modified EHEC. As colloidal particles, silica and polystyrene latex were used. The dispersed colloidal particles lowered the cloud point temperature at low polymer concentrations for all EHEC-particle combinations. This particle-induced phase separation is discussed in terms of surface effects.

Influence of Added Particles on the Phase Behavior of Polymer Solutions. Analysis by Mean-Field Lattice Theory

“…A third possible scenario in adsorbing polymer−particle mixtures is a capillary-induced phase separation (CIPS). − CIPS has recently been discovered in polymer solutions that are close to phase separation even in the absence of particles. The basic physics of a CIPS is that a new phase, the “capillary phase”, can be formed in the gap between the colloidal particles, if the interfacial free energy between the capillary phase and the particle surface is lower than between the original “reservoir phase” and the surface .…”

“…The aim of this work is to model how the phase behavior of a polymer solution is affected by added particles to which the polymer adsorbs. Previously, an experimental study from our group has shown that added particles enhance the phase separation in aqueous solutions of ethyl(hydroxyethyl)cellulose (EHEC) . In the latter experiments, EHEC adsorbed to the particles but the polymer-to-particle ratio was high, making bridging unlikely as the destabilizing mechanism.…”

Influence of the functionalization pattern of ethyl cellulose on the interactions with polystyrene latex particles in aqueous mixtures

“…For EHEC, Malmsten and Tiberg [11] showed that EHEC adsorb onto macroscopically polystyrene surfaces. It is evident that EHEC adsorbs onto PSL particles [12,13]. For CMC, Wallström et al [12] concluded from viscosity measurements that CMC does not adsorb onto PSL particles, which was in accordance to a more systematic study of Backfolk [14] giving that CMC does not adsorb onto latex particles based on other types of polymers than polystyrene.…”

Influence of added surfactant on particle flocculation in waterborne polymer–particle systems

“…The degrees of substitution were previously determined using gas chromatography. 5 The numbers for these are given as DS ethyl and MS EO , referring to the average number of substituents per glucose unit of the cellulose backbone. The only difference in structure between EHEC and HM-EHEC is that a few hydrophobic grafts are introduced onto the cellulose backbone in HM-EHEC.…”

“…5 The molecular weights and the polydispersity indexes were determined by size exclusion chromatography. 5 The molecular weights of EHEC and HM-EHEC were approximately 5 · 10 5 Da, and the polydispersity indexes are M w /M n » 6 for both polymers (Table 1).…”