Zhang Tao, Guo Mengfan, Jiang Jianyong, Zhang Xueyou, Lin Yuanhua, Nan Ce-Wen, Shen Yang
State Key Lab of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University Beijing 100084 China
RSC Adv. 2019 Nov 5;9(62):35990-35997. doi: 10.1039/c9ra06933j. eCollection 2019 Nov 4.
Polymer nanocomposite dielectrics, composed of polymer matrices with high breakdown strength and nanofillers with high dielectric constant, can achieve outstanding energy density. However, the great difference of intrinsic surface properties between the polymer and nanofillers will lead to poor compatibility and thus damage the dielectric properties of the composites. Introducing a transition layer to the filler surface can effectively reduce the degree of mismatch. In this work, we use a "direct polymerization" method to synthesize core-shell BaTiO nanoparticles (BTO_nps) with three types of stable and dense fluoro-polymer shells, , poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA), poly(2,2,3,4,4,4-hexafluorobutyl methacrylate) (PHFBMA), and poly(1,1,7-dodecafluoroheptyl methacrylate) (PDFHMA), and individually disperse them into the poly(vinylidene fluoride--hexafluoro propylene) (P(VDF-HFP)) matrix. Benefitting from the good interaction between the fluorine-containing segments in the shell polymer and the matrix segments, the dispersion of core-shell BTO_nps and their compatibility with P(VDF-HFP) are improved, which leads to a significant improvement in the dielectric properties of the nanocomposites. The results show that BTO@PDFHMA/P(VDF-HFP) composite exhibits an ultrahigh energy density of 16.8 J cm at 609 MV m with particle loading amount of 15 wt%, compared to 11.5 J cm at 492 MV m for a conventional solution blended BTO/P(VDF-HFP) composite. Meanwhile, the discharge efficiency is enhanced from ∼62 to ∼78%. It is elucidated that the core-shell strategy can achieve improved particle dispersion and dielectric properties. We consider that this simple method can well achieve the preparation of core-shell structures in dielectric nanocomposites.
由具有高击穿强度的聚合物基体和高介电常数的纳米填料组成的聚合物纳米复合电介质能够实现优异的能量密度。然而，聚合物与纳米填料之间固有表面性质的巨大差异会导致相容性较差，从而损害复合材料的介电性能。在填料表面引入过渡层可以有效降低不匹配程度。在本工作中，我们采用“直接聚合”方法合成了具有三种稳定且致密的含氟聚合物壳层的核壳型钛酸钡纳米颗粒（BTO_nps），即聚（甲基丙烯酸2,2,2 - 三氟乙酯）（PTFEMA）、聚（甲基丙烯酸2,2,3,4,4,4 - 六氟丁酯）（PHFBMA）和聚（甲基丙烯酸1,1,7 - 十二氟庚酯）（PDFHMA），并将它们分别分散到聚（偏二氟乙烯 - 六氟丙烯）（P(VDF - HFP)）基体中。得益于壳层聚合物中含氟链段与基体链段之间的良好相互作用，核壳型BTO_nps的分散性及其与P(VDF - HFP)的相容性得到改善，这导致纳米复合材料的介电性能显著提高。结果表明，BTO@PDFHMA/P(VDF - HFP)复合材料在粒子负载量为15 wt%、电场强度为609 MV/m时表现出16.8 J/cm³的超高能量密度，相比之下，传统溶液共混的BTO/P(VDF - HFP)复合材料在电场强度为492 MV/m时的能量密度为11.5 J/cm³。同时，放电效率从约62%提高到约78%。结果表明，核壳策略能够实现粒子分散性和介电性能的改善。我们认为这种简单方法能够很好地实现介电纳米复合材料中核壳结构的制备。
