writer：Rong Yang, Lv Ding, Weilong Chen, Xin Zhang, Jinchun Li
keywords：Main-chain liquid crystalline polymer, phase structure, molecular-weight dependence, rheological behaviour
source：期刊
specific source：Liquid Crystals
Issue time：2019年
In this article, the molecular-weight dependence of the phase structure, rheological behaviour and thermal stability of a main-chain liquid crystalline polyester (PBDPS) with strong π–π interaction was investigated in details by differential scanning calorimetry, polarising optical microscopy, wide-angle X-ray diffraction, dynamic oscillatory rheological measurements and thermogravimetric analysis. While the molecular weight of PBDPS is 5.2k, it shows smectic B and smectic A phases prior to isotropic phase. With increasing molecular weight, smectic B phase of PBDPS gradually disappeared. Moreover, the smecitc B to smectic A (Tlc) and smectic A to isotropic (Ti) phase transition temperatures decreased as increased molecular weight. The rheology results suggested that fluid type of PBDPSs changed from Newtonian fluid to pseudo-plastic fluid as the molecular weight of PBDPS increased. In addition, the zero-shear viscosity (η0) of PBDPS showed a power law relationship (η0 / Mw4:210:16) with molecular weight of PBDPS. All the PBDPSs showed good thermal stability with an initial decomposition temperature higher than 360°C.