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Multiple Sol-Gel Transitions of PEG-PCL-PEG Triblock Copolymer Aqueous Solution

✍ Scribed by Min Ji Hwang; Min Kyung Joo; Bo Gyu Choi; Min Hee Park; Ian W. Hamley; Byeongmoon Jeong

Publisher
John Wiley and Sons
Year
2010
Tongue
English
Weight
361 KB
Volume
31
Category
Article
ISSN
1022-1336

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✦ Synopsis

Abstract

An aqueous solution of a poly(ethylene glycol)‐polycaprolactone‐poly(ethylene glycol) (PEG‐PCL‐PEG) with a composition of EG~13~CL~23~EG~13~ undergoes multiple transitions, from sol‐to‐gel (hard gel)‐to‐sol‐to‐gel (soft gel)‐to‐sol, in the concentration range 20.0∼35.0 wt.‐%. Through dynamic mechanical analysis, UV‐vis spectrophotometry, small angle X‐ray scattering, differential scanning calorimetry, microcalorimetry and ^13^C 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. magnified image

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