Multiple sol-gel transitions of PEG-PCL-PEG triblock copolymer aqueous solution

Min Ji Hwang, Min Kyung Joo, Bo Gyu Choi, Min Hee Park, Ian W. Hamley, Byeongmoon Jeong

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

An aqueous solution of a poly(ethylene glycol)-polycaprolactone- poly(ethylene glycol) (PEG-PCL-PEG) with a composition of EG13CL 23EG13 undergoes multiple transitions, from sol-to-gel (hard gel)-to-sol-to-gel (soft gel)-to-sol, in the concentration range 20.0â35.0wt.-%. Through dynamic mechanical analysis, UV-vis spectrophotometry, small angle X-ray scattering, differential scanning calorimetry, microcalorimetry and 13C NMR spectroscopy, the mechanism of these transitions was investigated. The hard gel and soft gel are distinguished by the crystalline and amorphous state of the PCL. The extent of PEG dehydration and the molecular motion of each block also played a critical role in the multiple transitions. This paper suggests a new mechanism for these multiple transitions driven by temperature changes. An aqueous solution of EG13CL23EG13 undergoes sol-to-gel (hard gel)-to-sol-to-gel (soft gel)-to-sol multiple transitions, where the hard gel and soft gel are distinguished by crystalline and amorphous state of the PCL. The mechanism of transitions and molecular characteristics in each phase are investigated.

Original languageEnglish
Pages (from-to)2064-2069
Number of pages6
JournalMacromolecular Rapid Communications
Volume31
Issue number23
DOIs
StatePublished - 1 Dec 2010

Keywords

  • block copolymers
  • crystallization
  • hydrogels
  • poly(Îμ-caprolactone)
  • stimuli-sensitive polymers

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