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氰乙基纤维素在二甲基甲酰胺、二甲基乙酰胺、二甲基亚砜、乙腈以及丙酮等溶剂中可以形成溶致性液晶。随浓度增加,溶液从各向同性状态经两相共存态转变成为完全的液晶态。升高温度到T_c,液晶相消失;降低温度到T′_c,液晶相再生成。T_c总大于T′_c。而且,浓度越高,过冷温度△T=T_c—T′_c越小。在各向同性,两相共存或完全的液晶状态,溶液平均折射率和消光度均与浓度呈线性关系。但在两相间相互转变时,即在C_1~*和C_2~*处,n-C和 A-C 曲线上出现转折点。高聚物与溶剂的相互作用参数X_(12)愈小,临界浓度C_1~*愈小。把描述大分子链柔顺性的参数f与X_(12)联系起来,可用 1956年 Flory的理论定性地解释溶剂对高聚物溶致性液晶形成的影响。
Cyanoethyl cellulose can form lyotropic liquid crystals in solvents such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetonitrile and acetone. With the increase of concentration, the solution changes from the isotropic state to the complete liquid crystal state through the coexistence of two phases. Increase the temperature to T_c, the liquid crystal phase disappears; lower the temperature to T’_c, liquid crystal phase regeneration. T_c is always larger than T’_c. Moreover, the higher the concentration, the smaller the subcooling temperature ΔT = T_c-T’_c. In the isotropic, two-phase coexistence or complete liquid crystal state, the average refractive index and extinction of the solution are linear with the concentration. However, when the two phases change each other, there are turning points on n-C and A-C curves at C_1 ~ * and C_2 ~ *. The smaller the interaction parameter between polymer and solvent, X_ (12), the smaller the critical concentration C_1 ~ *. Linking the parameter f, which describes the flexibility of a macromolecular chain, with X_ (12), the 1956 Flory theory can be used to qualitatively explain the effect of solvents on the formation of polymer-induced lyotropic liquid crystals.