Phase-transition characteristics of amphiphilic poly(2-ethyl-2-oxazoline)/poly(ε-caprolactone) block copolymers in aqueous solutions

Chulhee Kim, Sang Cheon Lee, Suk Won Kang, Ick Chan Kwon, Seo Young Jeong

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Amphiphilic diblock and triblock copolymers of various block compositions based on hydrophilic poly(2-ethyl-2-oxazoline) (PEtOz) and hydrophobic poly(ε-caprolactone) were synthesized. The micelle formation of these block copolymers in aqueous media was confirmed by a fluorescence technique and dynamic light scattering. The critical micelle concentrations ranged from 35.5 to 4.6 mg/L for diblock copolymers and 4.7 to 9.0 mg/L for triblock copolymers, depending on the block composition. The phase-transition behaviors of the block copolymers in concentrated aqueous solutions were investigated. When the temperature was increased, aqueous solutions of diblock and triblock copolymers exhibited gel-sol transition and precipitation, both of which were thermally reversible. The gel-sol transition- and precipitation temperatures were manipulated by adjustment of the block composition. As the hydrophobic portion of block copolymers became higher, a larger gel region was generated. In the presence of sodium chloride, the phase transitions were shifted to a lower temperature level. Sodium thiocyanate displaced the gel region and precipitation temperatures to a higher temperature level. The low molecular weight saccharides, such as glucose and maltose, contributed to the shift of phase-transition temperatures to a lower temperature level, where glucose was more effective than maltose in lowering the gel-sol transition temperatures. The malonic acid that formed hydrogen bonds with the PEtOz shell of micelles was effective in lowering phase-transition temperatures to 1.0 M, above which concentration the block copolymer solutions formed complex precipitates.

Original languageEnglish
Pages (from-to)2400-2408
Number of pages9
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume38
Issue number18
DOIs
Publication statusPublished - 2000 Sep 15
Externally publishedYes

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block copolymers
Block copolymers
Phase transitions
gels
aqueous solutions
copolymers
micelles
transition temperature
Gels
glucose
Polymethyl Methacrylate
Sols
Superconducting transition temperature
Maltose
carbohydrates
Micelles
sodium chlorides
low molecular weights
Temperature
temperature

ASJC Scopus subject areas

  • Materials Chemistry
  • Polymers and Plastics

Cite this

Phase-transition characteristics of amphiphilic poly(2-ethyl-2-oxazoline)/poly(ε-caprolactone) block copolymers in aqueous solutions. / Kim, Chulhee; Lee, Sang Cheon; Kang, Suk Won; Kwon, Ick Chan; Jeong, Seo Young.

In: Journal of Polymer Science, Part B: Polymer Physics, Vol. 38, No. 18, 15.09.2000, p. 2400-2408.

Research output: Contribution to journalArticle

Kim, Chulhee ; Lee, Sang Cheon ; Kang, Suk Won ; Kwon, Ick Chan ; Jeong, Seo Young. / Phase-transition characteristics of amphiphilic poly(2-ethyl-2-oxazoline)/poly(ε-caprolactone) block copolymers in aqueous solutions. In: Journal of Polymer Science, Part B: Polymer Physics. 2000 ; Vol. 38, No. 18. pp. 2400-2408.
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