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Please use this identifier to cite or link to this item: http://hdl.handle.net/10119/17047

Title: Introducing planar hydrophobic groups into an alkyl-sulfonated rigid polyimide and how this affects morphology and proton conductivity
Authors: Nagao, Yuki
Tanaka, Teppei
Ono, Yutaro
Suetsugu, Kota
Hara, Mitsuo
Wang, Guangtong
Nagano, Shusaku
Abe, Takashi
Keywords: sulfonated polyimide
thin film
organized structure
proton conductivity
lyotropic liquid crystalline property
Issue Date: 2019-01-23
Publisher: Elsevier
Magazine name: Electrochimica Acta
Volume: 300
Start page: 333
End page: 340
DOI: 10.1016/j.electacta.2019.01.118
Abstract: Effects on organized structure and proton conductivity by the introduction of hydrophobic groups into the sulfonated polyimide backbone were investigated. A new sulfonated random co-polyimide with ion exchange capacity (IEC) of 2.69 meq. g^<-1> was synthesized. In our previous reports, we demonstrated that alkyl-sulfonated polyimide (ASPI-2, IEC = 3.11 meq. g^<-1>) thin film consisting of pyromellitic dianhydride and 3,3′-bis(3-sulfopropoxy)¬benzidine exhibits the organized lamellar structure and high in-plane proton conduction over 10^<-1> S cm^<-1> based on a lyotropic liquid crystalline (LC) property. However, the origin of the lyotropic LC property in the sulfonated polyimide thin films was not clear. In this paper, 20% hydrophobic o-tolidine was introduced into the ASPI-2 polymer backbone to suppress the lyotropic LC property. To discuss the effect on the organized structure and proton conductivity by the introduction of the hydrophobic groups, domain size, internal nanostructure, proton conductivity, water uptake, and proton dissociation from sulfonic acid groups were investigated by polarized optical microscopy, grazing incidence small-angle X-ray scattering, impedance measurements, quartz crystal microbalance, and Fourier transform infrared spectroscopy. The random co-polyimide thin film exhibited the birefringence and in-plane oriented lamellar structure. The lamellar distance was expanded up to 3.0 nm by water uptake. The lamellar expansion, molecular ordering, and proton dissociation showed similar behaviors by water uptake compared to the previous ASPI-2 thin film. Proton conductivity and water uptake per sulfonic acid group exhibited relatively high value of 3.2×10^<-2> S cm^<-1> and 12.5 at relative humidity (RH) = 95% and 298K. The estimated mobility of proton carriers decreased by 74% at λ = 12.5. Results suggest that the 20% substitution by hydrophobic monomers does not affect the structural difference but leads to the strong mobility decrease of proton carriers rather than the decrease of number of density.
Rights: Copyright (C)2019, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International license (CC BY-NC-ND 4.0). [http://creativecommons.org/licenses/by-nc-nd/4.0/] NOTICE: This is the author's version of a work accepted for publication by Elsevier. Yuki Nagao, Teppei Tanaka, Yutaro Ono, Kota Suetsugu, Mitsuo Hara, Guangtong Wang, Shusaku Nagano, Takashi Abe, Electrochimica Acta, 300, 2019, 333-340, https://doi.org/10.1016/j.electacta.2019.01.118
URI: http://hdl.handle.net/10119/17047
Material Type: author
Appears in Collections:c10-1. 雑誌掲載論文 (Journal Articles)

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