Synthesis and characterization of a nematic fully aromatic polyester based on biphenyl 3,4′-dicarboxylic acid
Synthesis and characterization of a nematic fully aromatic polyester based on biphenyl 3,4′-dicarboxylic acid
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DOI：
10.1039/c9py00683d
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发表时间：
2019-08-21
影响因子：
4.6
通讯作者：
Long, Timothy E.
中科院分区：
文献类型：
--
作者：
Heifferon, Katherine, V;Spiering, Glenn A.;Long, Timothy E.
以3，4 '-联苯甲酸联苯酯（HQ-3，4' BB）为扭折单体，通过对苯二酚的熔融酸解聚合，合成了一种新型液晶聚合物聚（HQ-3，4 '-联苯甲酸联苯酯）。选择氢醌二乙酸酯（HQ（a））或氢醌二特戊酸酯（HQ（p））分别促进褐色或白色最终聚合物。1H-1 NMR光谱证实了用对苯二酚的任一衍生物合成的聚合物的一致的聚合物主链结构。聚（HQ-3，4 ′ BB）在约480 ℃时开始出现重量损失，与市售的LCP相似。差示扫描量热法（DSC）和动态力学分析（DMA）显示玻璃化转变温度（T-g）为190 ℃，各向同性温度（T-i）接近330 ℃。熔融温度（Tm）的观察取决于聚合物的热历史。广角X-射线散射（WAXS）和偏光显微镜（POM）证实了淬火冷却后从各向同性状态的玻璃形态的形成。随后在280 ℃下退火或机械变形诱导聚合物结晶。流变学研究表明，在340 ℃下，聚（HQ-3，4 ′ BB）和RD 501在幂律区域中具有相似的剪切稀化行为。零剪切粘度测量表明，HQ（a）在相同的聚合条件下相对于HQ（p）提供更高的熔体粘度，表明更高的分子量。
Melt acidolysis polymerization of hydroquinone with a kinked monomer, biphenyl 3,4 '-bibenzoate, afforded a novel liquid crystalline polymer (LCP), poly(p-phenylene 3,4 '-bibenzoate) (poly(HQ-3,4 ' BB)). Selection of hydroquinone diacetate (HQ(a)) or hydroquinone dipivilate (HQ(p)) facilitated either a tan or white final polymer, respectively. H-1 NMR spectroscopy confirmed consistent polymer backbone structure for polymers synthesized with either derivative of hydroquinone. Poly(HQ-3,4 ' BB) exhibited the onset of weight loss at about 480 degrees C, similar to commercially available Vectra (R) LCP. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) revealed a glass transition temperature (T-g) of 190 degrees C and an isotropic temperature (T-i) near 330 degrees C. The observation of a melting temperature (T-m) depended upon the thermal history of the polymer. Wide-angle X-ray scattering (WAXS) and polarized optical microscopy (POM) confirmed the formation of a nematic glass morphology after quench-cooling from the isotropic state. Subsequent annealing at 280 degrees C or mechanical deformation induced crystallization of the polymer. Rheological studies demonstrated similar shear thinning behavior for poly(HQ-3,4 ' BB) and Vectra (R) RD501 in the power law region at 340 degrees C. Zero-shear viscosity measurements indicated that HQ(a) afforded higher melt viscosities after identical polymerization conditions relative to HQ(p), suggesting higher molecular weights.