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Thermal And Rheological Properties Of A Liquid-Crystalline Polyurethane, William Macknight, Peter J. Stenhouse, Enrique M. Valles, Simon W. Kantor
Thermal And Rheological Properties Of A Liquid-Crystalline Polyurethane, William Macknight, Peter J. Stenhouse, Enrique M. Valles, Simon W. Kantor
William MacKnight
A novel liquid-crystalline polyurethane (LCPU) was synthesized by the condensation of
2,4-toluenediisocyanate and 4,4'-bis(6-hydroxyhexoxy)biphenyl. Solution polymerization in dimethylformamide
produced intrinsic viscosities in the range 0.30-0.57 dL/g. Differential scanning calorimetry shows a crystalline
melting transition that is highly dependent on molecular weight and thermal history and a clearing transition
that is virtually independent of both. Parallel-plate rheometry results are consistent with the presence of
a liquid-crystalline phase, coexisting with a small amount of three-dimensional crystallinity, between 152 and
166 °C. Dynamic mechanical measurements reveal an unusually high elastic modulus of 180 MPa in the plateau
region above Tg, compared with 6 …