联苯类液晶单体及其聚合物的合成、结构与性能

合成了4种液晶单体M1~M4和对应的聚合物P1~P4.所合成的单体及聚合物的结构与液晶性能通过了FT-IR,DSC,TGA,POM和XRD的表征.研究表明,单体M1和M2呈现互变向列相,M3呈现向列相和近晶A(SA)相、近晶C(SC)相和近晶B(SB)相,M4呈现向列相和单变SA相、SC相和SB相;聚合物P1和P2呈现向列相,P3和P4呈现SA相和向列相.末端为乙氧基的单体和聚合物比末端为乙基的单体和聚合物具有较高的熔点(tm)、玻璃化温度(tg)和液晶清亮点(ti).此外,端基柔性较好的化合物倾向于形成近晶相.聚合物P1~P4具有宽的液晶相温度范围和高的热稳定性.

Synthesis, Structures and Properties of Liquid-Crystalline Monomers/Polymers Containing Biphenyl Groups

Four LC (liquid-crystalline) monomers (M1-M4) and their corresponding polymers (P1-P4) were synthesized, and their LC structures and properties were characterized with FT-IR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarizing optical microscopy (POM) and X-ray diffraction (XRD). The results showed that M1 and M2 present the enantiotropic nematic phase, M3 presents the nematic phase with SA, SC and SB smectic phases and M4 presents the nematic phase with SA, SC and SB monotropic phases. As to the polymers, P1 and P2 present the nematic phase, P3 and P4 present the SA phase with nematic phase. The melting temperature (tm), glass transition temperature (tg) and clearing point (ti) of monomers/polymers with terminal ethoxyl group are all proved higher than those with terminal ethyl group. Moreover, the monomers/polymers with the flexible spacer group tend to form smectic phase. TGA showed that the polymers P1-P4 all have wide LC temperature ranges and high thermal stability.