Web Release Date: March 16,
Confined Discotic Liquid Crystalline Self-Assembly in a Novel Coil-Coil-Disk Triblock Oligomer
and
Polymer Program, Institute of Materials Science and Department of Chemical Engineering, The University of Connecticut, Storrs, Connecticut 06269-3136, and Chemistry Department, State University of New York at Stony Brook, Stony Brook, New York 11794-3400
Received November 22, 2004
Revised Manuscript Received January 31, 2005
Abstract:
An asymmetric ABC coil-coil-disk triblock oligomer, based on polyethylene-block-poly(ethylene oxide)-block-pentakis(pentyloxy)triphenylene (PE-b-PEO-b-P5T or EEO-P5T), was successfully
synthesized by coupling a hydroxyl-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 the supramolecular self-assembly in bulk EEO-P5T were studied by differential scanning calorimetry, small- and
wide-angle X-ray scatterings, polarized light microscopy, and transmission electron microscopy. The PE
block crystallized into interdigitated, extended chain crystals with a chain-tilting angle of 23
from the
lamellar normal. The peak melting temperature (Tm) of the PE crystals was at 93.8 C. The PEO block
remained in the amorphous state because of its both ends being tethered to other two blocks and the
mismatch of the cross-section areas at the PE-PEO and PEO-P5T interfaces. Bilayer P5Ts, sandwiched
between amorphous PEO layers, exhibited a nematic columnar (Ncol) to nematic discotic (ND) transition
at ca. 23 C. Intriguingly, the ND to isotropic (or vice versa) transition was observed to coincide with the
melting (or crystallization) of the PE block.
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