Confined Discotic Liquid Crystalline Self-Assembly in a Novel Coil-Coil-Disk Triblock Oligomer

ORAL

Abstract

An asymmetric ABC coil-coil-disk triblock oligomer, based on polyethylene-\textit{block}-poly(ethylene oxide)-\textit{block}-pentakis(pentyloxy)triphenylene (PE-$b$-PEO-$b$-P5T or EEO-P5T), was successfully synthesized by coupling a hydroxyl group terminated PE-$b$-PEO diblock oligomer and 2-hydroxy-3,6,7,10,11-pentakis(pentyloxy)triphenylene using oxalyl chloride. The structure and morphology of supramolecular self-assembly in bulk EEO-P5T was studied by small- and wide-angle X-ray scatterings and transmission electron microscopy. The PE block was found to crystallize into interdigitated, extended chain crystals with a chain-tilting angle of 23$^{\circ}$ from the lamellar normal, where their melting temperature ($T_{m})$ was at 93.8$^{\circ}$ C. The PEO block remained in the amorphous state because both its ends were tethered to other two blocks. Bilayer P5Ts, sandwiched between amorphous PEO layers, exhibited a nematic columnar (N$_{col})$ to nematic discotic (N$_{D})$ transition at \textit{ca.} 23$^{\circ}$ C. Intriguingly, the N$_{D}$ to isotropic (or \textit{vise versa}) transition was observed to coincide with the melting (or crystallization) of the PE block.

*This work was supported by NSF CAREER award DMR-0348724.

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Authors

  • Li Cui

  • Jianjun Miao

    • Polymer Program, Institute of Materials Science and Department of Chemical Engineering, The University of Connecticut, Storrs, CT 06269

  • Lei Zhu

    • Polymer Program, Institute of Material Science and Department of Chemical Engineering, University of Connecticut, Storrs, CT 06269-3136
    • Polymer Program, Institute of Materials Science and Department of Chemical Engineering, The University of Connecticut
    • Polymer Program, Institute of Materials Science and Department of Chemical Engineering, The University of Connecticut, Storrs, CT 06269-3136

  • Igors Sics

  • Benjamin Hsiao

    • Chemistry Department, State University of New York at Stony Brook, Stony Brook, NY 11794-3400