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Relaxation Dynamics and Underlying Mechanism of a Thermally Reversible Gel from Symmetric Triblock Copolymer

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Title: Relaxation Dynamics and Underlying Mechanism of a Thermally Reversible Gel from Symmetric Triblock Copolymer
Authors: Ye, Ya Nan Browse this author
Cui, Kunpeng Browse this author
Indei, Tsutomu Browse this author
Nakajima, Tasuku Browse this author
Hourdet, Dominique Browse this author
Kurokawa, Takayuki Browse this author
Gong, Jian Ping Browse this author →KAKEN DB
Issue Date: 26-Nov-2019
Publisher: American Chemical Society
Journal Title: Macromolecules
Volume: 52
Issue: 22
Start Page: 8651
End Page: 8661
Publisher DOI: 10.1021/acs.macromol.9b01856
Abstract: We report a novel thermally responsive system from poly(butyl methacrylate)-b-poly(methacrylic acid)-b-poly(butyl methacrylate) (PBMA-b-PMAA-b-PBMA) triblock copolymer in dimethylformamide (DMF) solvent. This system shows a sol–gel transition by cooling below a critical temperature Tc. The network relaxation times of these gels rightly fall in the typical rheological experiment window, permitting us to investigate the relaxation dynamics and underlying mechanism, with a combination of linear rheology, time-resolved small-angle X-ray scattering (SAXS), and temperature-elevated nuclear magnetic resonance (NMR) measurements. Both time–temperature superposition (TTS) and time–concentration superposition (TCS) are well held in this system. The relaxation dynamics at temperatures below and above Tc are quite different, giving two different activation energies E1a and E2a, respectively. The E1a, being polymer concentration independent, is related to micelle formation of end-blocks, while the concentration dependent E2a is related to the chain friction of entangled polymer solution. By coupling linear rheology, SAXS, and NMR, we quantitatively estimated the fraction of bridge, loop, and dangling chains. The longest relaxation time of the gel, τL, strongly depends on polymer concentration, which is attributed to the increased connectivity of the micellar network. By combining the shift factors aT and aC determined from TTS and TCS, respectively, we can obtain the τL at any given temperature and concentration from that at reference temperature and concentration.
Rights: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Macromolecules, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see
Type: article (author version)
Appears in Collections:生命科学院・先端生命科学研究院 (Graduate School of Life Science / Faculty of Advanced Life Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 龔 剣萍 (Gong Jian Ping)

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