Synthesis and Thermoreversible Gelation Properties of Main-Chain Poly(pyridine-2,6-dicarboxamide-triazole)s

Authors

  • Sui-Lung Yim,

    1. Department of Chemistry, The Chinese University of Hong Kong, Shatin, HKSAR, Fax: (+852) 26035057
    2. Center of Novel Functional Molecules and Institute of Molecular Functional Materials (UGC-AoE Scheme), CUHK, Shatin, HKSAR
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  • Prof. Hak-Fun Chow,

    Corresponding author
    1. Department of Chemistry, The Chinese University of Hong Kong, Shatin, HKSAR, Fax: (+852) 26035057
    2. Center of Novel Functional Molecules and Institute of Molecular Functional Materials (UGC-AoE Scheme), CUHK, Shatin, HKSAR
    • Department of Chemistry, The Chinese University of Hong Kong, Shatin, HKSAR, Fax: (+852) 26035057
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  • Prof. Man-Chor Chan,

    1. Department of Chemistry, The Chinese University of Hong Kong, Shatin, HKSAR, Fax: (+852) 26035057
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  • Prof. Chi-Ming Che,

    1. Department of Chemistry, The University of Hong Kong and Institute of Molecular Functional Materials (UGC-AoE Scheme), HKU, Pokfulam Road, HKSAR
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  • Dr. Kam-Hung Low

    1. Department of Chemistry, The University of Hong Kong and Institute of Molecular Functional Materials (UGC-AoE Scheme), HKU, Pokfulam Road, HKSAR
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Abstract

A series of main-chain poly(amide-triazole)s were prepared by copper(I)-catalyzed alkyne–azide AABB-type copolymerizatons between five structurally similar diacetylenes 15 with the same diazide 6. The acetylene units in monomers 15 possessed different degrees of conformational flexibility due to the different number of intramolecular hydrogen bonds built inside the monomer architecture. Our study showed that the conformational freedom of the monomer had a profound effect on the polymerization efficiency and the thermoreversible gelation properties of the resulting copolymers. Among all five diacetylene monomers, only the one, that is, 1-Py(NH)2 which possesses the pyridine-2,6-dicarboxamide unit with two built-in intramolecular H bonds could produce the corresponding poly(amide-triazole) Poly-(PyNH)2 with a significantly higher degree of polymerization (DP) than other monomers with a lesser number of intramolecular H bonds. In addition, it was found that only this polymer exhibited excellent thermoreversible gelation ability in aromatic solvents. A self-assembling model of the organogelating polymer Poly-(PyNH)2 was proposed based on FTIR spectroscopy, XRD, and SEM analyses, in which H bonding, π–π aromatic stacking, hydrophobic interactions, and the structural rigidity of the polymer backbone were identified as the main driving forces for the polymer self-assembly process.

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