Journal of Industrial and Engineering Chemistry, Vol.6, No.5, 338-342, September, 2000
Thermal Properties of Liquid-Crystalline Polyurethanes Containing Biphenylene Mesogenic Units
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A series of thermotropic polyurethanes containing mesogenic units was synthesized by the polyaddition reaction of diisocyanates such as 2,6-toluene diisocyanate (SG-TDI), 2,5-toluene diisocyanate (2,5-TDI), 2,4-toluene diisocyanate (2,4-TDI), and 1,4-phenylene diisocyanate (1,4-PDI) with 4,4'-bis(6-hydroxyhexyloxy)biphenyl (BP6). The polyurethanes, 2,6-TDI/BP6, 2,5-TDI/BP6, and 2,4-TDI/BP6, showed liquid crystallinity in the cooling scan under shearing. For example, a para-type 2,5-TDI/BP6 exhibited liquid crystallinity in the temperature range from 200 ℃ to 178 ℃ and a meta-type 2,4-TDI/BP6 exhibited liquid crystallinity in the temperature range from 132 ℃ to 111 ℃ in the cooling scan. The thermal behavior was investigated using differential scanning calorimetry (DSC), polarizing microscopy, and X-ray diffractometry.
Keywords:Polyurethanes;Mesogenic Unit;Diisocyanates;4,4'-Bis(6-hydroxyhexyloxy)biphenyl;Differential Scanning Calorimetry
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