联苯型热致性液晶聚氨酯的合成与表征

Synthesis and Characterization of the Thermotropic Liquid Crystalline Polyurethane Containing Biphenyl

采用溶液聚合法,以4,4′-二羟基联苯、5-氯-1-戊醇、甲苯-2,4-二异氰酸酯（2,4-TDI）及三种不同链长的脂肪族二元醇为原料制备了一系列的联苯型液晶聚氨酯（LCPU）。采用红外光谱（FT-IR）、差示扫描量热（DSC）、偏光显微镜（POM）和X射线衍射（WAXD）等手段对聚合物进行表征。结果表明,这类联苯型的LCPU的熔点（Tm）随着聚合物分子链中小分子二元醇链长的增加而降低,而各向同性温度（Ti）则变化不大;POM观察表明,这一系列的聚合物均为热致性向列型液晶,其液晶态温度区间在90℃-207℃;其广角X射线衍射图在2θ≈25°有尖锐的衍射峰。

A series of thermotropic liquid crystalline polyurethane（LCPU） were synthesized by polyaddtion reaction of 2,4-tolylene dissocyanate（2,4-TDI） with aliphatic diols and 4,4′-bis（5-hydroxypentoxy）biphenyl in N,-dimethylformamide（DMF） solution.The liquid crystalline behaviour and properties of the LCPU were investigated with differential scanning calorimetry（DSC）,polarized optical microscope（POM）,wide angle X-ray diffraction（WAXD）.The melting point（Tm） of LCPU decreases and the temperature range of the liquid crystal phase of the polyurethane becomes wider with the increase of the length of diol flexibls spacers in polyurethane,while isotropic temperature（Ti） remains almost unchanged. The LCPU exhibits nematic phase with a schlieren texture（or threaded texture） and has wider mesophase temperature ranges.The WAXD results show that LCPU owns a dispersive peak at 2θ near 20°,and a strong diffraction peak at 2θ near 25°