Highly Oriented Liquid Crystalline Epoxy Film: Robust High Thermal-Conductive Ability
Highly Oriented Liquid Crystalline Epoxy Film: Robust High Thermal-Conductive Ability
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DOI：
10.1021/acsomega.7b02088
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发表时间：
2018-03
期刊：
影响因子：
4.1
通讯作者：
Shingo Tanaka;F. Hojo;Y. Takezawa;K. Kanie;A. Muramatsu
中科院分区：
文献类型：
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作者：
Shingo Tanaka;F. Hojo;Y. Takezawa;K. Kanie;A. Muramatsu
研究了液晶（LC）环氧树脂（LCER）的分子取向对导热系数的影响，其导热系数取决于经物理表面处理改性的非晶态钠-石灰-硅玻璃基板表面的表面自由能。结果表明，LC环氧单体在具有71.3和72.7 mN m-1高表面自由能的基体表面形成了同向取向的SmA相，而在具有46.3 mN m-1低表面自由能的基体表面形成了平面取向。光学显微镜观察和x射线分析表明，LC环氧单体由于在高自由能表面与固化剂交联而诱导了同向取向的SmA结构。根据掠入射小角x射线散射图计算得到的各向同性SmA结构的取向序参数为0.73 ~ 0.75。交联LCER形成同向热带排列的SmA结构的导热系数在Sm层法向的平均值和最大值分别为2.0和5.8 W m-1 K-1。在热固性聚合物和陶瓷玻璃中，LCER的热导率值显著，可用于高导热胶粘剂和电子电气器件的包装材料。
The molecular orientation effect of a liquid crystalline (LC) epoxy resin (LCER) on thermal conductivity was investigated, with the thermal conductivity depending on the surface free energy of amorphous soda–lime–silica glass substrate surfaces modified using physical surface treatments. The LC epoxy monomer was revealed to form a smectic A (SmA) phase with homeotropic alignments on the surfaces of substrates that possess high surface free energies of 71.3 and 72.7 mN m–1, but forming a planar alignment on the surface of a substrate that possesses a relatively low surface free energy of 46.3 mN m–1. The optical microscopy observations and the X-ray analyses revealed that the LC epoxy monomer also induced a homeotropically aligned SmA structure due to cross-linking with a curing agent on the high-free-energy surface. The orientational order parameter of the resulting homeotropic SmA structure was calculated from the grazing incidence small-angle X-ray scattering patterns to be 0.73–0.75. The thermal conductivity of the cross-linked LCER forming a homeotropically aligned SmA structure was also estimated to be 2.0 and 5.8 W m–1 K–1 for the average and maximum in the direction of the Sm layer normal. The value of the thermal conductivity was remarkable among the thermosetting polymers and ceramic glass, and the LCER could be applied for high-thermal-conductive adhesives and packaging materials in electrical and electronic devices.