近年来，电子元器件的小型化和高度集成化，导致器件功率密度急剧上升。长期高温运行将缩短元器件的使用效率和工作寿命。散热问题在极大程度上制约了行业发展。导热聚合物具有良好的电绝缘性能、加工性能、机械性能成为解决器件散热问题的关键材料。然而，绝大多数聚合物材料的由于微观分子链的无规则排列导致导热系数偏低，难以直接运用于散热领域。通过向聚合物材料中引入高导热填料粒子来提升聚合物的导热性能成为了最简便、高效的手段，常用的导热填料有氧化铝、氮化铝、石墨烯等。受制于填料分散性和界面相容性，直接将导热填料与聚合物混合制备导热聚合物复合材料，导热性能提升效果难以达到预期。本论文以氮化硼纳米片（BNNS）为填料，从提高BNNS的分散性和界面相容性入手，采用化学改性法对BNNS进行表面功能化，同时以环氧-硫醇（Epoxy-thiol）聚合物和液晶/环氧-硫醇（LCM/Epoxy-thiol）聚合物为基体，制备了一系列功能化氮化硼纳米片填充的环氧-硫醇聚合基导热复合材料，并进行了力学性能、红外光谱（FT-IR）、X射线衍射（XRD）、X射线光电子光电子能谱（XPS）、扫描电子显微镜（SEM）、导热系数等表征测试，系统研究了功能化氮化硼纳米片对复合材料微观结构和导热性能的影响，主要研究内容如下：

    （1）采用单烷氧基焦磷酸酯型钛酸酯偶联剂（MPTCA）对BNNS进行了表面功能化改性，成功制备了表面功能化改性BNNS（f-BNNS）。结果表明BNNS表面功能化改性成功，改性前后BNNS的晶格结构未发生改变，MPTCA的最佳使用量为4.8 wt%。

    （2）分别采用BNNS和f-BNNS为填料，以Epoxy-thiol聚合物为基体，采用混合-浇铸法制备了BNNS/Epoxy-thiol和f-BNNS/Epoxy-thiol复合材料膜。结果表明，相同含量填料情况下，f-BNNS/Epoxy-thiol 薄膜的拉伸强度和断裂伸长率要优于BNNS/Epoxy-thiol膜。f-BNNS 均匀分散于Epoxy-thiol 基体内，与基体界面结合紧密，导热系数测试结果表明，f-BNNS/Epoxy-thiol 膜具有更好的导热系数。当f-BNNS含量为30 wt%时，f-BNNS/ Epoxy-thiol 膜的导热系数达到1.41 W/m·K，相比于纯Epoxy-thiol提升了420.37%。

    （3）采用高温热固化-浇铸工艺，以f-BNNS 为填料，LCM/Epoxy-thiol为基体，制备了f-BNNS/LCM/Epoxy-thiol膜。结果表明，LCM在f-BNNS/LCM/Epoxy-thiol膜内仍然保持有序性，形成的球粒有序结构分布于f-BNNS片层之间。f-BNNS在f-BNNS/LCM/ Epoxy-thiol膜内保持良好的分散性和界面相容性。当f-BNNS含量为30 wt%时，f-BNNS/ LCM/Epoxy-thiol膜的导热系数提升至1.35 W/m·K，相比于LCM/Epoxy-thiol膜提升了98.38%。

    （4）采用高压电场-高温热固化-浇铸工艺，以f-BNNS 为填料，LCM/Epoxy-thiol为基体，在电场环境下制备了E-f-BNNS/LCM/Epoxy-thiol膜。结果表明，电场作用可以显著提高E-f-BNNS/LCM/Epoxy-thiol膜的微观有序性，LCM在E-f-BNNS/LCM/Epoxy-thiol膜内仍保持有序性。当f-BNNS含量为10 wt%时，E-f-BNNS/LCM/Epoxy-thiol膜微观结构显示含有鱼鳞状有序结构，f-BNNS嵌插在鱼鳞结构中，保持良好的分散性和界面相容性。当f-BNNS含量为30 wt%时，E-f-BNNS/LCM/Epoxy-thiol膜的微观形成f-BNNS均匀分布在球状结构之间，两者协同构成了连续热导通路。导热系数测试结果表明，当f-BNNS含量为30 wt%时，E-f-BNNS/LCM/Epoxy-thiol 薄膜的导热系数达到1.65 W/m·K，相比于E-LCM/Epoxy-thiol薄膜提升了111.68%。

   In recent years, the miniaturization and high integration of electronic devices have led to a sharp rise in power density. Excessive heat accumulation will affect its quality stability, thus greatly shortening its service life of electronic devices. The heat dissipation problem has greatly restricted the development of the industry. Owing to the excellent electrical insulation performance, high flexibility, lightweight, high strength, chemical resistance, low cost and easy processability, thermally conductive polymers have widely used in electronic devices to manage heat dissipation issues. However, the thermal conductivity of most polymers is low due to the random entanglement of molecular chains, which far from meeting the increasing demand for thermal conduction/dissipation capabilities of electrical equipment or electronic components of electronic devices. The most common, simple, and effective method for thermal conductivity improvement is to fill polymer matrix with highly thermally conductive fillers. The commonly used thermally conductive fillers are alumina, aluminum nitride, graphene, and so on. This kind of thermal conductive composites are called filler-type polymer composites. Due to the poor dispersion of fillers and low interfacial compatibility, it is difficult to achieve the expected improvement of thermal conductivity by directly mixing thermally conductive fillers with polymers to prepare filler-type polymer composites. In this paper, boron nitride nanosheets (BNNS) were used to perform surface functionalization of BNNS by chemical modification method, improving the dispersibility and interfacial compatibility. A series of boron nitride-based thermal conductive composites were prepared by using flexible epoxy-thiol (Epoxy-thiol) polymer and liquid crystal monomer/Epoxy-thiol (LCM/Epoxy-thiol) polymer as a matrix and characterized by mechanical Performance, infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermal conductivity and other tests. Systematically investigated the effect of functionalized boron nitride nanosheets on the microstructure and thermal conductivity of composites. The main research contents of this paper are as follows:

    (1) The surface functional modified BNNS (f-BNNS) was successfully prepared by using monoalkoxy pyrophosphate titanate coupling agent (MPTCA).  The results showed that the surface functionalization of BNNS was successful, and the lattice structure of BNNS were not changed before and after functionalization. The optimal amount of MPTCA was 4.8 wt%.

    (2) BNNS/Epoxy-thiol films and f-BNNS/Epoxy-thiol films were prepared by mixing- casting method using BNNS and f-BNNS as fillers and Epoxy-thiol polymer as matrix, respectively. The results showed that the tensile strength and elongation at break of f-BNNS/ Epoxy-thiol films were better than those of BNNS/Epoxy-thiol films with the same filler content. The f-BNNS were uniformly dispersed in the Epoxy-thiol matrix and had good interfacial compatibility with matrix. The thermal conductivity test results showed that the f-BNNS/Epoxy- thiol films were better than that of BNNS/Epoxy-thiol films. When the f-BNNS content was 30 wt%, the thermal conductivity of f-BNNS/Epoxy-thiol film reached 1.41 W/m·K, which was 420.37% higher than that of pure Epoxy-thiol film.

   (3) The f-BNNS/LCM/Epoxy-thiol films were prepared by high temperature thermal curing-casting process with f-BNNS as filler and LCM/Epoxy-thiol as matrix. The results showed that LCM still maintained the ordered arrangement within the f-BNNS/LCM/Epoxy- thiol film, and the formed spherical ordered structure is distributed between the f-BNNS. f-BNNS maintained good dispersion and interfacial compatibility within f-BNNS/ LCM/Epoxy- thiol films. When the content of f-BNNS was 30 wt%, the thermal conductivity of f-BNNS/ LCM/Epoxy-thiol film was improved to 1.35 W/m·K, which was 98.38% higher than that of LCM/Epoxy-thiol film.

    (4) E-f-BNNS/LCM/Epoxy-thiol films were prepared by high voltage electric field-high temperature thermal curing-casting process with f-BNNS as filler and LCM/Epoxy-thiol as matrix. The results showed that the electric field can significantly improve the microscopic order of the E-f-BNNS/LCM/Epoxy-thiol film, and the LCM still maintained the ordered arrangement within the f-BNNS/LCM/Epoxy-thiol film. When the f-BNNS content was 10 wt%, the E-f- BNNS/LCM/Epoxy-thiol film microscopically formed squamous ordered structures. The f-BNNS were uniformly dispersed and embedded in the squamous ordered structure, and maintained good interfacial compatibility. When the content of f-BNNS was 30 wt%, the microscopic formation of E-f-BNNS/LCM/Epoxy-thiol film formed f-BNNS uniformly distributed in the spherical structure, which constituted continuous thermal conduction paths. The thermal conductivity test results showed that the thermal conductivity of the E-f-BNNS/ LCM/Epoxy-thiol film reached 1.65 W/m·K with 30 wt% f-BNNS content, compared to E-LCM/Epoxy-thiol film increased by 111.68%.

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