POSS封口介孔二氧化硅/聚合物复合材料的介电性能与微观结构调控

The dielectric properties of Mesoporous silicas(MPS)/polymer composites are strongly affect by the void content and interface structure. However, this composites have the possibility to enhance the void content and interface action. Moreover,the mechanism of effects of microstructure on the dielectric properties of the nanoporous composites is not clear now.In this proposal, a series of porous silica, named as POSS-MPS, with active surface, covered entrance of mesopores and lower polarity are synthesized by the reaction of polyhedral oligomeric silsesquioxane(POSS) with epoxy group and MPS with amice group. Therefore, the controlled and larger porosity, and excellent interface with strong action between the filler and polymer in this nanoporous composites are obtained.Accordingly,the controlled and lower dielectric constant of the nanoporous silica/polymer composites are achieved. Moreover, the toughness, strength, modulus and heat resistance of the nanoporous composites are improved due to the organic-inorganic structure of POSS-MPS. The chemical and physical structure of POSS-MPS are precisely characterized, in order to figure out it's influence on the microstructure of POSS-MPS/polymer composites. The dielectric properties and the microstructures (including distribution of void and filler, interface structure, porosity, etc) of these composites are characterized to explain the corelationship of dielectric properties and microstructure. The results of above-mentioned research is helpful to discover the mechanism of dielectric properties of composites modified with nanoporous silicas. This project provides the theoretical and practical basis to prepare lower dielectric constant composite with improved performance, and benefit high-frenquency electronic circuit and aircraft and aerospace materials.

介孔二氧化硅（MPS）/聚合物复合材料的介电性能与材料的空隙含量及界面结构密切相关。但聚合物向介孔的填充降低了复合材料的空隙率，且MPS与聚合物的相容性不好，现有的介电理论不能系统地阐明这种纳米孔二氧化硅改性聚合物介电性能的作用机理。本项目提出利用反应性笼形倍半硅氧烷（POSS）与MPS反应制备介孔孔口被POSS部分封闭、具有活性表面、低极性的POSS-MPS，提高POSS-MPS/聚合物复合材料的空隙含量，并利用POSS与聚合物的化学键合提高界面强度，降低复合材料的介电系数并提高韧性。研究POSS-MPS的物理、化学结构对复合材料的微观结构以及介电性能的影响规律，阐明影响POSS-MPS/聚合物复合材料介电性能的关键结构因素。在上述研究的基础上，揭示纳米孔二氧化硅改性聚合物介电性能的机理，为制备高性能的低介电系数复合材料提供理论和实践基础。

介孔二氧化硅（MPS）/聚合物复合材料的介电性能与材料的空隙含量及界面结构密切相关。聚合物向介孔的填充降低了复合材料的空隙率，且MPS与聚合物的相容性不好，现有的介电理论不能系统地阐明这种纳米孔二氧化硅改性聚合物介电性能的作用机理。本研究利用反应性笼形倍半硅氧烷（POSS）与MPS反应制备介孔孔口被POSS部分封闭、具有活性表面、低极性的POSS-MPS，提高POSS-MPS/聚合物复合材料的空隙含量，并利用POSS与聚合物的化学键合提高界面强度，降低复合材料的介电系数并提高韧性。.利用八环氧基POSS及单氨基POSS与MPS反应制备了具有微-介孔结构的有机-无机杂化二氧化硅粒子G-POSS-MPS以及NH2-POSS-MPS。粒子中保留大量孔隙，POSS主要分布在MPS外表面形成冠状结构并对介孔封闭，并为与CE的反应提供官能团。相对于G-POSS，NH2-POSS合成的POSS-MPS具有更大孔容。通过调整POSS:MPS质量比、MPS结构、POSS-MPS制备工艺等可实现对POSS-MPS的结构调控。.POSS-MPS与CE的化学键合使之在CE中均匀而稳定地分散并形成强界面作用。因POSS的柔性结构而形成的柔性界面及由POSS带来的自由体积增大，使POSS-MPS/CE复合材料韧性有明显提高。相对于NH2-POSS-MPS/CE，G-POSS-MPS/CE复合材料的交联密度更高，韧性略差，但强度和模量提高较明显。.POSS-MPS的引入在POSS-MPS/CE复合材料中形成大量孔隙，有效地降低了复合材料的介电系数和介电损耗。因NH2-POSS-MPS/CE中孔隙含量更大，且极性基团更少，因而相较于G-POSS-MPS/CE有更低的介电系数和介电损耗。.研究成果揭示纳米孔二氧化硅改性聚合物介电性能的机理，为制备高性能的低介电系数复合材料提供理论和实践基础。