石墨烯/环氧树脂多层次界面的构筑及其复合材料导电、力学性能研究

The nice dispersion and interfacial compatibility of graphene in epoxy matrix is the key to prepare conductive graphene/epoxy composites with high performance. However, the covalent or non-covalent modification of graphene, as the common method to improve the dispersion and interfacial compatibility of the graphene, cannot balance the electrical properties and mechanical properties of the graphene/epoxy composites. To address this issue, in this project, the π–π interaction between forestry resource ‘tannin’ and graphene will be utilized to fabricate tannin non-covalent modified graphene. Then, various non-covalent and covalent hierarchically modified graphene will be designed through the mannich reaction between polyamine and the tannin which is adsorbed on the surface of the graphene, or the amidation reaction between polyamine and carboxyl group at the edge of the graphene. And high performance graphene/epoxy composites with balanced electrical properties and mechanical properties will be fabricated by using the non-covalent and covalent hierarchically modified graphene to modify epoxy resin. The structures' characterization and the properties of graphene/epoxy resin composites will be studied in multiple scales. And the influence of interfacial construction method, the ratio of the covalent bond to the non-covalent bond, grafting chain length and et al. on the graphene dispersion and the electrical and mechanical properties of graphene/epoxy composites will be studied to reveal the influence of interfacial structures on the properties of the composites and its internal mechanism. The research results of this project will offer the theoretical foundation for designing conductive graphene/polymer composites with high performance.

石墨烯在环氧树脂中的有效分散和良好的界面相容性是制备高性能石墨烯/环氧树脂导电复合材料的关键，然而目前常用的共价键或非共价键修饰的方法都不能兼顾材料的导电和力学性能。为此，本项目拟利用林业资源单宁与石墨烯的π-π相互作用制备出单宁非共价键修饰的石墨烯，再通过多元胺与石墨烯附着的单宁之间的Mannich反应、多元胺与石墨烯边缘羧基的酰胺化反应设计出多种非共价键-共价键多层次修饰的石墨烯，利用非共价键-共价键多层次修饰的石墨烯改性环氧树脂，制备出导电和力学性能都兼顾的高性能石墨烯/环氧树脂复合材料。在多尺度范围内对石墨烯/环氧树脂复合材料的结构及性能进行表征和研究，探讨界面构筑方式、共价键和非共价键比例、接枝链长等对石墨烯分散性及复合材料导电、力学性能的影响，揭示界面结构对复合材料性能的影响规律及其内在机理，为设计高性能石墨烯/高分子导电复合材料提供理论依据。

本项目研究目的在于制备出同时具有优异导电性能和韧性的环氧树脂复合材料。本项目从增韧剂改性环氧树脂、表面修饰碳材料改性环氧树脂以及环氧树脂导电复合材料多级结构的调控这几方面展开研究，取得了如下成果：.1.利用桐油含有共轭π-π结构，通过Diels-Alder加成等反应合成出可与环氧树脂形成牺牲氢键或π-π相互作用的桐油基环氧增韧剂。研究表明牺牲键的引入在维持较高的力学强度和模量下大幅改善环氧树脂的柔韧性。含有牺牲氢键的桐油基环氧增韧剂（30wt%添加量）改性环氧树脂的断裂伸长率、拉伸韧性和无缺口冲击强度相对于纯环氧树脂分别提高了338.6%、145.2%和261.8%，其拉伸强度仍保持在38.4MPa；含有牺牲π-π相互作用的桐油基环氧增韧剂（7.5wt%添加量）改性环氧树脂的断裂伸长率、拉伸韧性和缺口冲击强度相对于纯环氧树脂分别提高了1367.8%、804.8%和37.2%，其拉伸强度仍能保持在34.8MPa。.2.利用单宁酸及其衍生物与碳材料形成π-π相互作用的特点对石墨烯/碳纳米管碳杂化材料进行修饰，制备出可与环氧树脂形成多重牺牲键的碳杂化材料。研究发现碳材料/环氧树脂构筑的多重牺牲键在保持环氧树脂的强度和模量下，大幅提高环氧树脂的柔韧性：1）多重牺牲π-π相互作用的构筑导致极低含量碳材料的添加（0.01wt%）就能显著地改善环氧树脂力学性能（拉伸强度、杨氏模量、断裂伸长率、断裂韧性KIC和GIC分别提高23.3%、44.6%、41.2%、114.6%和219.3%），且导电逾渗阈值极低（逾渗阈值为0.076wt%）；2）氢键和π-π相互作用多重牺牲键的构筑导致超低含量碳材料的添加（0.001wt%）就能大幅度地提高环氧树脂柔韧性（断裂伸长率和拉伸韧性分别提高541.8%和755.4%），并保持环氧树脂的强度和模量。.3.利用碳纳米管与桐油基环氧树脂和双酚A型环氧树脂相互作用的不同，自组装形成具有“细胞结构”的环氧树脂复合材料，从而创制出性能优异的环氧树脂导电复合材料，其不但具有高强度、高模量的优点，而且其导电逾渗阈值极低（导电逾渗阈值为0.032wt%）、其韧性为目前已知碳纳米管/环氧树脂导电复合材料中最高的（韧性为32.50MJ/m3）。.通过本项目的研究，发现牺牲键在对环氧树脂产生优异增韧效果同时还保持其它优良的性能，具有极高的理论和应用价值。