College Park, Maryland June 6 - 10 , 2004 |
WP16: Structure of a Liquid Crystalline Polymer In an Amorphous Polymer Matrix
R. Metha, M. D. Dadmun (Department of Chemistry, University of Tennessee, Knoxville, TN 37923)
Molecular composites, composed of uniformly dispersed rigid-rod liquid crystalline polymer (LCP) molecules in a flexible amorphous polymer matrix, have remained hitherto elusive due to a scarcity of miscible systems containing a LCP and an amorphous polymer. The production of such a blend with a large miscibility window, which is experimentally accessible, has become possible by modifying the architecture of the flexible polymer, so as to induce favorable enthalpic interactions between the flexible polymer and LCP. Specifically, liquid crystalline polyurethanes (LCPU) are found to be miscible with a copolymer of styrene and vinyl phenol. Here miscibility is promoted by realizing intermolecular hydrogen bonding between the carbonyl groups of the urethane linkages with the hydroxyl groups present in the styrenic matrix.
Availability of a truly miscible molecular composite presents a unique opportunity of studying the confirmation of polymer chains containing rigid-rods that are uniformly dispersed in a flexible coil matrix. A system consisting of the LCPU and the deuterated styrenic copolymer containing 10% vinyl phenol is examined by Small Angle Neutron Scattering at the National Center for Neutron Research at the National Institute of Standard and Technology, and the Institute of Solid State Research (IFF) at Jülich. The radius of gyration of the LCPU is determined by fitting the low angle portion of the scattering curve to the traditional Guinier and Zimm methods. The conformation of LCPU molecules is also determined by analysis of the scattering curve using a wormlike model and Kratky Porod analysis.
Support towards this work by NSF DMR-0241214, The Joint Institute of Neutron Sciences at the University of Tennessee, NCNR (NIST), and IFF (FZ-Jülich) is gratefully acknowledged.
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