碳纳米管选择性清除自由基的规律及机理研究

With wide service temperature and excellent oil and chemical resistance, fluorosilicone rubber (FVMQ) becomes the unique material used in high technology area of nation. However, when serving at high temperature, FVMQ could suffer serious ageing problem due to the chain reaction of free radicals. Traditional antioxidants such as phenols are not appropriate to prevent the ageing problem due to their inhibition to vulcanizers as well as their bad durability. Fortunately, in our latest investigation, we have found a few addition amount of carbon nanotubes could significantly improve the heat resistance and flame retardance of FVMQ, and most important of all, they can hardly inhibit the vulcanization when using some kinds of vulcanizers. Based on this important finding, the project aims to investigate the scavenging activity of CNTs towards various of radicals using experimental approach, and obtain the relative stabilization energy of the corresponding radicals using the quantum chemical calculations. Finally, a universal law and the mechanism of CNTs to scavenge different radicals will be established by the combination of experimental and calculation results.

氟硅橡胶具有优异的耐高低温、耐油耐化学腐蚀等性能，是国家尖端领域无法替代的关键材料之一。然而在高温下使用时也会因自由基连锁反应而出现严重的老化降解问题，采用传统抗氧剂（如酚类）预防老化不仅会影响橡胶的硫化，而且效果无法持久。因此，能够发现既可以清除导致橡胶老化的自由基，同时又不影响橡胶硫化的技术一直是学界努力目标。有幸我们最近研究发现，少量碳纳米管（CNTs）能够显著提高氟硅橡胶耐老化性能和阻燃性能，而且完全不会影响某些自由基对橡胶的硫化。基于此重要发现，本项目拟通过实验方法深入研究CNTs对多种自由基的清除能力，采用量化计算得到对应自由基的相对稳定化能，建立两者之间的对应关系，发现普适性的规律，创建对不同自由基的清除机理。

改善氟硅橡胶的耐热性能对尖端科技领域的发展有重要意义。研究中发现加入微量的碳纳米管能显著提高氟硅橡胶的热氧老化性能。本项目主要内容是研究有机硅橡胶的硫化和老化过程中，碳纳米管对不同自由基所表现出的不同清除作用规律，探究碳纳米管清除自由基的机理。实验数据和量子化学计算结果表明，稳定性低的自由基（RSE值小的）容易被碳纳米管清除，分子呈平面结构的自由基易被碳纳米管捕获（两者有较高的结合能）。关于碳纳米管清除自由基的机理，我们提出并验证了碳纳米管在芳香醌结构附近含有弥散的单电子分布，致使多个碳原子具有与活泼自由基反应的能力。这也解释了碳纳米管显著提高氟硅橡胶耐热性能的原因。本研究为开发更高效的抗氧剂和耐热剂提供了理论指导，为碳纳米管化学的发展开启了新的方向。