Xiao Zhong, Kunpeng Ruan and Junwei Gu*. Enhanced Thermal Conductivities of Liquid Crystal Polyesters from Controlled Structure of Molecular Chains by Introducing Different Dicarboxylic Acid Monomers. Research, 2022, 2022: 9805686. 2021IF=11.036.（1區綜合類Top期刊，2021中國最具國際影響力學術期刊）
https://doi.org/10.34133/2022/9805686
Abstract
Enhancing thermal conductivity coefficient (λ) of liquid crystal polyesters would further widen their application in electronics and electricals. In this work, a kind of biphenyl-based dihydroxy monomer is synthesized using 4, 4’-biphenyl (BP) and triethylene glycol (TEG) as raw material, which further reacts with three different dicarboxylic acids (succinic acid, p-phenylenediacetic acid and terephthalic acid, respectively) by melt polycondensation to prepare intrinsically highly thermally conductive poly 4’, 4’’’-[1, 2-ethanediyl-bis(oxy-2, 1-ethanediyloxy)]-bis(p-hydroxybiphenyl) succinate (PEOS), poly 4’, 4’’’-[1, 2-ethanediyl-bis(oxy-2, 1-ethanediyloxy)]-bis(p-hydroxybiphenyl) p-phenyldiacetate (PEOP) and poly 4’, 4’’’-[1, 2-ethanediyl- bis(oxy-2, 1-ethanediyloxy)]- bis(p-hydroxybiphenyl) terephthalate (PEOT), collectively called biphenyl-based liquid crystal polyesters (B-LCPE). The results show that B-LCPE possess the desired molecular structure, exhibit smectic phase in liquid crystal range and semicrystalline polymers at room temperature, and possess excellent intrinsic thermal conductivities, thermal stabilities, and mechanical properties. λ of PEOT is 0.51 W/(m·K), significantly exceeds that of polyethylene terephthalate (0.15 W/(m·K)) which has similar molecular structure with PEOT, and also higher than that of PEOS (0.32 W/(m·K)) and PEOP (0.38 W/(m·K)). The corresponding heat resistance index (THRI), elasticity modulus and hardness of PEOT are 174.6oC, 3.6 GPa and 154.5 MPa, respectively, also higher than those of PEOS (162.2oC, 1.8 GPa and 83.4 MPa) and PEOP (171.8oC, 2.3 GPa and 149.6 MPa).
本文以4,4’-二羥基聯苯（BP）和三乙二醇（TEG）為主要原料合成了一種聯苯型液晶二羥基單體，并分別與丁二酸、1,4-亞苯基二乙酸和對苯二甲酸熔融縮聚，配合澆注成型工藝制備聚丁二酸{4'',4-[1,2-乙二基雙(氧基-2,1-乙二氧基)]-雙(對羥基聯苯)}酯（PEOS）、聚1,4-亞苯基二乙酸{4'',4-[1,2-乙二基雙(氧基-2,1-乙二氧基)]-雙(對羥基聯苯)}酯（PEOP）和聚對苯二甲酸{4'',4-[1,2-乙二基雙(氧基-2,1-乙二氧基)]-雙(對羥基聯苯)}酯（PEOT）三種聯苯型液晶聚酯（統稱為B-LCPE）。結果表明，具有預期分子結構的B-LCPE表現出近晶相液晶性，室溫下為半結晶性高分子；B-LCPE均表現出優異的本體導熱性能、熱穩定性和力學性能。PEOT具有最佳的綜合性能，本體導熱系數（λ）高達0.51 W/(m·K)，較分子結構相似的聚對苯二甲酸乙二醇酯（PET，λ為0.15 W/(m·K)）提升了240.0%，也優于PEOS（0.32 W/(m·K)）和PEOP（0.38 W/(m·K)）；相應的耐熱指數（THRI）、彈性模量和硬度分別為174.6oC、3.6 GPa和154.5 MPa，也均優于PEOS（162.2oC、1.8 GPa、83.4 MPa）和PEOP（171.8oC、2.3 GPa和149.6 MPa）。
本文亮點
1. 相比PEOS和PEOP，PEOT具有較強的結晶能力和較高的結晶度，分子間強的π-π堆積作用賦予PEOT更加有序的分子層內和層間的排列取向。
2. PEOT的本體λ高達0.51 W/(m·K)，較具有相似分子結構的聚對苯二甲酸乙二醇酯（PET，λ為0.15 W/(m·K)）提升了240.0%，也優于PEOS（0.32 W/(m·K)）和PEOP（0.38 W/(m·K)）。
3. PEOT具有優異的熱穩定性和力學性能。其耐熱指數（THRI）、彈性模量和硬度分別為174.6oC、3.6 GPa和154.5 MPa，均優于PEOS（162.2oC、1.8 GPa、83.4 MPa）和PEOP（171.8oC、2.3 GPa和149.6 MPa）。