Photo-healable ion gel with improved mechanical properties using a tetra-arm diblock copolymer containing azobenzene groups

Xiaofeng Ma, Ryoji Usui, Yuzo Kitazawa, Hisashi Kokubo, Masayoshi Watanabe

    • 6 Citations

    Abstract

    Photo-healable ion gels with improved mechanical properties are demonstrated using a tetra-arm diblock copolymer (A(B)4) containing azobenzene groups. Physical ion gels were prepared by self-assembly of A(B)4 in a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6), where A block is the ionic liquid-compatible tetra-PEG, and B block is the thermo-/photo-responsive random copolymer of 4-phenylazophenyl methacrylate and N-isopropylacrylamide (P(NIPAm-r-AzoMA)). The A(B)4 ion gels have a higher modulus and fewer network defects than the triblock copolymer (A(B)2) ion gel (A block is PEG; B block is P(NIPAm-r-AzoMA)). Self-standing A(B)4 ion gels were obtained at a lower polymer concentration than A(B)2 ion gels in [C4mim]PF6. The A(B)4/[C4mim]PF6 and A(B)2/[C4mim]PF6 binary systems exhibit low-temperature gel-states and high-temperature sol-states. The gel-to-sol transition temperature also depends on the photoisomerization state of the azobenzene moiety in the polymers. It is confirmed that photo-induced sol-gel transition is reversible at a suitable temperature. Photo-healable ion gels are demonstrated using the photo-induced reversible sol-gel transition, where damaged regions are UV-light-irradiated to induce the gel-to-sol transition then visible-light-irradiated to heal the gels by the sol-to-gel transition. Remarkable photo-healing efficiency in terms of the mechanical properties is realized by this procedure.

    Original languageEnglish
    Pages (from-to)42-50
    Number of pages9
    JournalPolymer
    Volume78
    DOIs
    StatePublished - 2015 Nov 5

    Fingerprint

    Gels
    Ions
    Sols
    Azobenzene
    Block copolymers
    Mechanical properties
    Temperature
    Ionic liquids
    Polyethylene glycols
    Sol-gels
    Polymers
    Photoisomerization
    Ultraviolet radiation
    Self assembly
    Superconducting transition temperature
    Copolymers
    Defects

    Keywords

    • Block copolymer
    • Ion gel
    • Ionic liquid
    • Photo-healable material
    • Photochromism
    • Upper critical solution temperature

    ASJC Scopus subject areas

    • Organic Chemistry
    • Polymers and Plastics

    Cite this

    Photo-healable ion gel with improved mechanical properties using a tetra-arm diblock copolymer containing azobenzene groups. / Ma, Xiaofeng; Usui, Ryoji; Kitazawa, Yuzo; Kokubo, Hisashi; Watanabe, Masayoshi.

    In: Polymer, Vol. 78, 05.11.2015, p. 42-50.

    Research output: Contribution to journalArticle

    Ma, Xiaofeng; Usui, Ryoji; Kitazawa, Yuzo; Kokubo, Hisashi; Watanabe, Masayoshi / Photo-healable ion gel with improved mechanical properties using a tetra-arm diblock copolymer containing azobenzene groups.

    In: Polymer, Vol. 78, 05.11.2015, p. 42-50.

    Research output: Contribution to journalArticle

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    author = "Xiaofeng Ma and Ryoji Usui and Yuzo Kitazawa and Hisashi Kokubo and Masayoshi Watanabe",
    year = "2015",
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    AU - Ma,Xiaofeng

    AU - Usui,Ryoji

    AU - Kitazawa,Yuzo

    AU - Kokubo,Hisashi

    AU - Watanabe,Masayoshi

    PY - 2015/11/5

    Y1 - 2015/11/5

    N2 - Photo-healable ion gels with improved mechanical properties are demonstrated using a tetra-arm diblock copolymer (A(B)4) containing azobenzene groups. Physical ion gels were prepared by self-assembly of A(B)4 in a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6), where A block is the ionic liquid-compatible tetra-PEG, and B block is the thermo-/photo-responsive random copolymer of 4-phenylazophenyl methacrylate and N-isopropylacrylamide (P(NIPAm-r-AzoMA)). The A(B)4 ion gels have a higher modulus and fewer network defects than the triblock copolymer (A(B)2) ion gel (A block is PEG; B block is P(NIPAm-r-AzoMA)). Self-standing A(B)4 ion gels were obtained at a lower polymer concentration than A(B)2 ion gels in [C4mim]PF6. The A(B)4/[C4mim]PF6 and A(B)2/[C4mim]PF6 binary systems exhibit low-temperature gel-states and high-temperature sol-states. The gel-to-sol transition temperature also depends on the photoisomerization state of the azobenzene moiety in the polymers. It is confirmed that photo-induced sol-gel transition is reversible at a suitable temperature. Photo-healable ion gels are demonstrated using the photo-induced reversible sol-gel transition, where damaged regions are UV-light-irradiated to induce the gel-to-sol transition then visible-light-irradiated to heal the gels by the sol-to-gel transition. Remarkable photo-healing efficiency in terms of the mechanical properties is realized by this procedure.

    AB - Photo-healable ion gels with improved mechanical properties are demonstrated using a tetra-arm diblock copolymer (A(B)4) containing azobenzene groups. Physical ion gels were prepared by self-assembly of A(B)4 in a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6), where A block is the ionic liquid-compatible tetra-PEG, and B block is the thermo-/photo-responsive random copolymer of 4-phenylazophenyl methacrylate and N-isopropylacrylamide (P(NIPAm-r-AzoMA)). The A(B)4 ion gels have a higher modulus and fewer network defects than the triblock copolymer (A(B)2) ion gel (A block is PEG; B block is P(NIPAm-r-AzoMA)). Self-standing A(B)4 ion gels were obtained at a lower polymer concentration than A(B)2 ion gels in [C4mim]PF6. The A(B)4/[C4mim]PF6 and A(B)2/[C4mim]PF6 binary systems exhibit low-temperature gel-states and high-temperature sol-states. The gel-to-sol transition temperature also depends on the photoisomerization state of the azobenzene moiety in the polymers. It is confirmed that photo-induced sol-gel transition is reversible at a suitable temperature. Photo-healable ion gels are demonstrated using the photo-induced reversible sol-gel transition, where damaged regions are UV-light-irradiated to induce the gel-to-sol transition then visible-light-irradiated to heal the gels by the sol-to-gel transition. Remarkable photo-healing efficiency in terms of the mechanical properties is realized by this procedure.

    KW - Block copolymer

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    KW - Photochromism

    KW - Upper critical solution temperature

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