Poly(2-cyano-p-phenylene terephthalamide) (CY-PPTA) has garnered significant interest as a promising precursor for super p-aramid fibers because of its organosolubility in N,N-dimethyl acetamide/lithium chloride (DMAc/LiCl) while conserving the superior properties of the resultant fibers. However, CY-PPTA has been reported to exhibit abnormal phase behavior owing to the strong dipole–dipole interactions induced by the cyano groups. Herein, we rheologically study the isotropic phases of CY-PPTA/DMAc solutions with respect to the concentration and temperature and compare them with those of CY-PPTA/sulfuric acid (H₂SO₄) solutions. In the isotropic region, the CY-PPTA solutions yield a higher power-law exponent of the dynamic viscosity (η') versus concentration of 6.0 (ηʹ ~ c^6.0) in the DMAc system than that in H₂SO₄ (ηʹ ~ c^3.2). Moreover, the CY-PPTA/DMAc solutions exhibit a lower critical solution temperature (LCST) behavior with increasing temperature, in contrast with the upper critical solution temperature in H₂SO₄. Consequently, the viscosity and exponent of the CY-PPTA/DMAc solutions increase at elevated temperatures. As shown by the Cole–Cole plot, the heterogeneity in the DMAc system becomes worse. The LCST of the CY-PPTA solution is ascribed to the intermolecular interactions between the highly polar cyano groups, which are negligible in H₂SO₄.

聚（2-氰基对苯二甲酰对苯二胺）（CY-PPTA）作为超级对位芳纶纤维的前体，因其在N , N-二甲基乙酰胺/氯化锂（DMAc/LiCl）中的有机溶解性而引起了人们的极大兴趣，同时保留所得纤维的优异性能。然而，据报道，由于氰基引发的强偶极-偶极相互作用，CY-PPTA 表现出异常的相行为。在此，我们从流变学角度研究了 CY-PPTA/DMAc 溶液在浓度和温度方面的各向同性相，并将其与 CY-PPTA/硫酸 (H ₂ SO ₄ ) 溶液的各向同性相进行比较。在各向同性区域， DMAc 体系中CY-PPTA 溶液在浓度为 6.0 ( ηʹ  ~  c ^{6.0 ) 时产生比 H} ₂ SO _{4中更高的动态粘度 (} η' )幂律指数( ηʹ  ~  c ) ^3.2）。_{此外，随着温度的升高，CY-PPTA/DMAc 溶液表现出较低的临界溶解温度（LCST）行为，这与 H 2} SO ₄中的较高临界溶解温度相反。因此，CY-PPTA/DMAc 溶液的粘度和指数在高温下增加。正如 Cole-Cole 图所示，DMAc 系统的异质性变得更差。CY-PPTA 溶液的LCST 归因于高极性氰基之间的分子间相互作用，这种相互作用在H ₂ SO ₄中可以忽略不计。