Multiple Phase Structures and Enhanced Dielectric Properties of Side-Chain Liquid Crystalline Polymer Containing Unique Biaxial Mesogen with Large Dipole Moment

IF 5.4 1区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY
GIANT Pub Date : 2024-06-13 DOI:10.1016/j.giant.2024.100305
Zi-Fan Yang , Le Zhou , Wei Xia , Lan-Ying Zhang , Huai Yang , Yang Shen , Shuang Yang , Er-Qiang Chen
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引用次数: 0

Abstract

To achieve all-organic polymer with high dielectric performances, we have designed a novel side-chain liquid crystalline polymer (P7) with strong polar mesogen of (Z)-4-(2-cyano-2-phenylvinyl)benzonitrile (CSCN) attached to polycyclooctene backbone. The bis-cyano-substituted CSCN is board-shaped and exhibits a large dipole moment (8.54 D) which tilts ∼34.2° away from its molecular long axis. Consequently, CSCN shows unique dual molecular anisotropy: one from biaxial shape anisotropy and the other from polarization anisotropy. The complex phase behaviors of P7 were investigated employing mainly the techniques of differential scanning calorimetry and X-ray diffraction. Four liquid crystal (LC) phases are identified as K0, K1, K2 and K3, which are SmA, highly-ordered biaxial SmA, B5-like and B7-like, respectively, with the thermal stability increased in sequence. The experimental results indicate that the different LC phases are arisen from the competition and balance between π-π stacking and dipole-dipole interaction. While the face-to-face π-π stacking is dominant in K0 and K1, optimizing the dipole-dipole interaction causes the CSCN mesogens within the smectic layer to tilt and rotate, resulting in K2 and K3. We further investigated the dielectric properties of P7 films using polarization-electric field loops test. The dielectric constant (εr) of P7 is found to be LC structure dependent, which is increased when the LC phase is varied from K0 to K3. With an average εr of 9.7 achieved in K3 and the low dielectric loss (tan δ = 0.001), P7 film offers a promising material in advanced applications like energy storage and electronic devices.

Abstract Image

含有大偶极矩独特双轴中间体的侧链液晶聚合物的多相结构和增强的介电性能
为了获得具有高介电常数性能的全有机聚合物,我们设计了一种新型侧链液晶聚合物(P7),该聚合物的聚环辛烯骨架上附有强极性介质(Z)-4-(2-氰基-2-苯基乙烯基)苯腈(CSCN)。双氰基取代的 CSCN 呈板状,具有较大的偶极矩(8.54 D),与分子长轴成 34.2° 的倾斜角。因此,CSCN 表现出独特的双分子各向异性:一种来自双轴形状各向异性,另一种来自极化各向异性。研究人员主要采用差示扫描量热法和 X 射线衍射技术对 P7 的复杂相行为进行了研究。确定了四种液晶(LC)相,分别为 K0、K1、K2 和 K3,它们分别是 SmA、高阶双轴 SmA、类 B5 和类 B7,其热稳定性依次增强。实验结果表明,不同的低浓相是由π-π堆叠和偶极-偶极相互作用之间的竞争和平衡引起的。在 K0 和 K1 中,面对面的 π-π 堆叠起主导作用,而优化偶极-偶极相互作用则会导致密相层中的 CSCN 介质倾斜和旋转,从而产生 K2 和 K3。我们利用极化-电场环测试进一步研究了 P7 薄膜的介电性能。我们发现 P7 的介电常数(εr)与 LC 结构有关,当 LC 相从 K0 变为 K3 时,介电常数增大。P7 薄膜在 K3 中的平均εr 值为 9.7,介电损耗较低(tan δ = 0.001),是一种很有前途的材料,可用于储能和电子设备等先进应用领域。
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来源期刊
GIANT
GIANT Multiple-
CiteScore
8.50
自引率
8.60%
发文量
46
审稿时长
42 days
期刊介绍: Giant is an interdisciplinary title focusing on fundamental and applied macromolecular science spanning all chemistry, physics, biology, and materials aspects of the field in the broadest sense. Key areas covered include macromolecular chemistry, supramolecular assembly, multiscale and multifunctional materials, organic-inorganic hybrid materials, biophysics, biomimetics and surface science. Core topics range from developments in synthesis, characterisation and assembly towards creating uniformly sized precision macromolecules with tailored properties, to the design and assembly of nanostructured materials in multiple dimensions, and further to the study of smart or living designer materials with tuneable multiscale properties.
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