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(qū)綜合類Top期刊，2021中國最具國際影響力學(xué)術(shù)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(lián)苯（BP）和三乙二醇（TEG）為主要原料合成了一種聯(lián)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(duì)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(duì)羥基聯(lián)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(duì)羥基聯(lián)苯)}酯（PEOP）和聚對(duì)苯二甲酸{4'',4-[1,2-乙二基雙(氧基-2,1-乙二氧基)]-雙(對(duì)羥基聯(lián)苯)}酯（PEOT）三種聯(lián)苯型液晶聚酯（統(tǒng)稱為B-LCPE）。結(jié)果表明，具有預(yù)期分子結(jié)構(gòu)的B-LCPE表現(xiàn)出近晶相液晶性，室溫下為半結(jié)晶性高分子；B-LCPE均表現(xiàn)出優(yōu)異的本體導(dǎo)熱性能、熱穩(wěn)定性和力學(xué)性能。PEOT具有最佳的綜合性能，本體導(dǎo)熱系數(shù)（λ）高達(dá)0.51 W/(m·K)，較分子結(jié)構(gòu)相似的聚對(duì)苯二甲酸乙二醇酯（PET，λ為0.15 W/(m·K)）提升了240.0%，也優(yōu)于PEOS（0.32 W/(m·K)）和PEOP（0.38 W/(m·K)）；相應(yīng)的耐熱指數(shù)（THRI）、彈性模量和硬度分別為174.6oC、3.6 GPa和154.5 MPa，也均優(yōu)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(diǎn)
1. 相比PEOS和PEOP，PEOT具有較強(qiáng)的結(jié)晶能力和較高的結(jié)晶度，分子間強(qiáng)的π-π堆積作用賦予PEOT更加有序的分子層內(nèi)和層間的排列取向。
2. PEOT的本體λ高達(dá)0.51 W/(m·K)，較具有相似分子結(jié)構(gòu)的聚對(duì)苯二甲酸乙二醇酯（PET，λ為0.15 W/(m·K)）提升了240.0%，也優(yōu)于PEOS（0.32 W/(m·K)）和PEOP（0.38 W/(m·K)）。
3. PEOT具有優(yōu)異的熱穩(wěn)定性和力學(xué)性能。其耐熱指數(shù)（THRI）、彈性模量和硬度分別為174.6oC、3.6 GPa和154.5 MPa，均優(yōu)于PEOS（162.2oC、1.8 GPa、83.4 MPa）和PEOP（171.8oC、2.3 GPa和149.6 MPa）。