title: Multiple Sol-Gel Transitions of PEG-PCL-PEG Triblock Copolymer Aqueous Solution.
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.
authors.affiliation: Department of Chemistry and Nano Sciences, Department of Bioinspired Science (WCU), Ewha Womans University, Seoul, 120-750, Korea.
authors.forename: Min Ji
authors.initials: MJ
authors.lastname: Hwang
authors.forename: Min Kyung
authors.initials: MK
authors.lastname: Joo
authors.forename: Bo Gyu
authors.initials: BG
authors.lastname: Choi
authors.forename: Min Hee
authors.initials: MH
authors.lastname: Park
authors.forename: Ian W
authors.initials: IW
authors.lastname: Hamley
authors.forename: Byeongmoon
authors.initials: B
authors.lastname: Jeong