Departamento de Química Física I, Facultad de Química, Universidad Complutense, 28040-Madrid, Spain.
J Phys Chem B. 2012 Aug 16;116(32):9846-59. doi: 10.1021/jp305907u. Epub 2012 Aug 7.
Liquid crystalline polymers (LCPs) are complex systems that include features of both orientationally ordered mesophases and amorphous polymers. Frequently, the isotropic amorphous state cannot be studied due to the rapid mesophase formation. Here, a new main chain LCP, poly(triethyleneglycol methyl p,p'-bibenzoate), PTEMeB, has been synthesized. It shows a rather slow mesophase formation making possible to study independently both the amorphous and the liquid crystalline states. The structure and phase transitions of PTEMeB have been investigated by calorimetry, variable-temperature MAXS/WAXS employing synchrotron radiation, and X-ray diffraction in oriented fibers. These experiments have pointed out the presence of two glass transitions, related to the amorphous or to the liquid crystal phases. Additionally, the mesophase seems to be a coexistence of orthogonal and tilted smectic phases. A dielectric relaxation study of PTEMeB over broad ranges of temperature and pressure has been performed. The dynamic glass transition turns out to be slower for the amorphous state than for the liquid crystal. Monitoring of the α relaxation has allowed us to follow the isothermal mesophase formation at atmospheric pressure. Additionally, the dynamical behavior at high pressures has pointed out the fast formation of the mesophase induced by sudden pressure changes.
液晶聚合物（LCPs）是一种复杂的体系，兼具各向同性有序介相和无定形聚合物的特点。通常，由于各向同性无定形相的迅速形成，无法对其进行研究。这里，我们合成了一种新型主链液晶聚合物，聚（三乙二醇甲基对，对'-联苯二甲酸酯），PTEMeB。其具有较慢的介相形成速度，从而可以分别独立地研究无定形相和液晶相。我们通过差示扫描量热法、利用同步辐射的变温广角 X 射线散射/小角 X 射线散射（MAXS/WAXS）以及取向纤维的 X 射线衍射研究了 PTEMeB 的结构和相转变。这些实验表明存在两个玻璃化转变，分别与无定形相或液晶相有关。此外，介相似乎是正交和倾斜层状相的共存。我们还对 PTEMeB 进行了宽温宽压介电弛豫研究。结果表明，无定形相的动态玻璃化转变比液晶相的更慢。对α弛豫的监测使我们能够在大气压下跟踪等温介相的形成。此外，高压下的动力学行为表明，介相的快速形成是由压力的突然变化引起的。
