Thermothropic liquid crystalline poly(urethane-urea)s from 4,4'-diaminobiphenyl, 2,4-tolylene diisocyanate
Polimery 1997, No 1, 55
Novel liquid crystalline poly(urethane-urea)s (PUU) were synthesized from 4,4'-diaminobiphenyl,2,4-tolylene diisocyanate (mesogenic unit) and poly(oxytetramethylene)diols (spacers). FTIR spectra revealed characteristic absorption bands (-NH- stretch, H-bonded urea's CO, -CH2- asym. stretch, etc.) and ones attributable to weaker interactions and less-ordered structures, consistent with the expected degree of phase separation in the polymer. DSC thermograms showed a flat endothermic peak (190°–200°C), a sharp first-order transition at 255°C (216°C for PUU-4) attributable to the melting of PUU para-crystalline regions, and a weak transition at ~300°C resulting in a low viscous liquid and followed by total decomposition of the polymer. Polarizing microscopy showed the polymer to be optically isotropic and to loose its integrity at temperatures close to those at the start of the DSC endotherm.
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