Phase Behavior in Aqueous Two-Phase Systems Containing

Mårten Svensson, Per Linse, Folke Tjerneld

Research output: Contribution to journalArticlepeer-review

Abstract

The phase behavior of the three-component PEO-PPO-PEO/dextradwater system has
been studied. Pluronic L64, P105, and F68 were used, and they are members of a family of triblock
copolymers with the structure PEO-PPO-PEO, where PEO is poly(ethy1ene oxide) and PPO poly-
(propylene oxide). Moreover, these triblock copolymers tend to self-aggregate in aqueous solution at
increasing temperature. The phase behavior of the three-component system was studied both experi-
mentally and theoretically at different temperatures corresponding to the unimer (monomolecular) and
the micellar region of the PEO-PPO-PEO polymers. The determination of the unimer and micellar
regions was performed with a dye solubilization technique using 1,6-diphenyl-1,3,5-hexatriene (DPH) as
a spectroscopic probe. A strong temperature effect on the phase behavior in PEO-PPO-PEO/dextrad
water systems was observed in the case of Pluronic L64 and P105. At elevated temperature (40 "C) the
micellization of the PEO-PPO-PEO polymers leads to a drastic change of the tie-line slopes as well as
the shape of the binodals. Qualitative agreements were found between experimental findings and
theoretical calculations using a Flory-Huggins lattice theory extended with internal degrees of freedom
by modeling the PEO-PPO-PEO polymers as a poly(ethy1ene oxide) chain. This supports the prevailing
picture that the more hydrophobic PPO block is shielded from water contacts by forming hydrophobic
domains surrounded by EO segments.
Original languageEnglish
Pages (from-to)3597-3603
JournalMacromolecules
Volume28
Issue number10
DOIs
Publication statusPublished - 1995

Subject classification (UKÄ)

  • Biological Sciences

Keywords

  • OXIDE) TRIBLOCK COPOLYMER
  • OXYPROPYLENE OXYETHYLENE)
  • LIGHT-SCATTERING
  • PROPYLENE-OXIDE
  • ETHYLENE-OXIDE
  • MICELLIZATION
  • SOLUBILIZATION
  • ASSOCIATION
  • PROBE

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