Liquid biphase systems formed in ternary mixtures of two organic solvents and ethylene oxide oligomers or polymers

Abstract

Este trabalho descreve estudos sobre o equilíbrio líquido-líquido em sistemas ternários contendo polímeros ou oligômeros de óxido de etileno, heptano e um de três diferentes solventes orgânicos (metanol, clorofórmio ou diclorometano). Os efeitos da temperatura, da massa molar do polímero e da natureza química do solvente polar sobre o equilíbrio de fase foram investigados. Para todos os sistemas, a região de miscibilidade diminuiu à medida que a temperatura era reduzida, indicando que o processo de separação de fases é exotérmico. Tanto para misturas binárias quanto ternárias, a miscibilidade também diminuía quando aumentava o tamanho da macromolécula, ainda que este efeito tenha sido bem menos significativo em sistemas ternários. Estas características sugerem que o processo de separação de fases nestes sistemas ternários seja mais afetado por contribuições entálpicas do que entrópicas. Com relação aos diferentes solventes polares usados, a menor região de miscibilidade foi verificada com metanol, em concordância com sua menor capacidade de solubilização de PEO. A maior miscibilidade foi verificada com clorofórmio, não muito diferente da observada com diclorometano. As linhas de amarração foram determinadas para alguns sistemas, confirmando a forte segregação entre o polímero e o heptano.Phase equilibrium data were determined for ternary systems containing ethylene oxide oligomers or polymers, heptane and one of three organic solvents (methanol, dichloromethane or chloroform). The effects of temperature, of polymer molecular weight and of the chemical nature of the organic solvent on phase equilibrium were investigated. For all the studied systems, the miscibility region was reduced as temperature decreased, indicating an exothermic phase separation process. For both binary and ternary mixtures, the miscibility also decreased as the macromolecule size increased, although this effect was less significant for the ternary mixtures. These features suggest that phase separation is more influenced by enthalpic than entropic contributions. Regarding the different polar solvents investigated, methanol presented a much smaller miscibility region, in accordance with its inferior solvation ability for PEO. The largest miscibility region was observed with chloroform, not much different from the behaviour observed with dichloromethane. Tie lines were determined for some systems, confirming the strong segregation between polymer and the hydrocarbon solvent.

Poly(ethylene glycol) or Poly(ethylene oxide)?: Magnitude of end-group Contribution to the Partitioning of Ethylene Oxide Oligomers and Polymers between Water and Organic Phases

“…The only difference is the slightly higher partition coefficients with chloroform for lower molar mass, a sequence opposite to that observed for PEO solubility. 10 The first striking point that arises from these data is that PEO begins to prefer the organic phase at quite low molar mass, 300 g mol -1 for chloroform and 400 g mol -1 for dichloromethane, indicating that its apolar nature (polyether) starts to prevail even for oligomers most commonly referred to as glycols. This fact may have important implications when analysing PEO partitioning in other systems.…”

High solids loading ceramic colloidal dispersions in UV curable media via comb-polyelectrolyte surfactants

“…PEO). PEO for example is soluble in water and compatible with a variety of polar organic solvents (alcohols, chloroform, 1,2-dichloroethane, acetonitrile, THF) and certain organic mixtures [41], but is not soluble for example in alkanes. Good dispersion of powders with adsorbed comb-polyelectrolyte in organic medium where the PEO side chains are soluble, is anticipated.…”

Entropically Driven Partitioning of Ethylene Oxide Oligomers and Polymers in Aqueous/Organic Biphasic Systems

“…A closed-loop phase diagram has been reported for aqueous solutions of PEO of certain molecular weights . PEO presents an opposite solubility behavior of UCST (upper critical solution temperature) type in some organic solvents. , Some of these features have recently been addressed by Israelachvili, commenting on “the different faces of PEO” and stressing the importance of a better understanding of its “unusual properties”, especially because of the PEO ubiquitous presence in commercial products and in industrial and biomedical processes.…”