复合材料熔融加工过程中氧化石墨烯的原位还原及相关问题

Graphene holds promising applications in polymer composites due to its large aspect ratio, outstanding mechanical properties, good thermal stability and high electrical conductivity. Considering the strong aggregation of graphene sheets in various polymer matrices, graphene oxide (GO) is commonly used as the starting material in place of graphene. In practice, GO itself is also potential filler for polymer composites for its large aspect ratio and high mechanical strength. Moreover, in view of its abundant oxygen-containing groups, GO shows more effective reinforcement effect than graphene for polar polymers. However, it is noteworthy that, whether polymer/graphene or polymer/GO is produced with GO as starting material, the resultant nanocomposites have to undergo melt processing before preparing specimens for mechanical measurements or manufacturing products for applications. This highly scalable and environmentally friendly processing technique will inevitably lead to the changes in chemical structure of GO and multi-scale physical structures of composite systems. Then, a "big" question naturally arises, that is, what happens during the melt-processing processes and what is responsible for these changes? Addressing these questions are important for understanding the nature of the melt-processing and developing the technique to contral the structure and properties of graphene-based polymer nanocomposites, and therefore be of great interest in both academic and industrial research. In this work, through the investigation on the chemical and physical changes of polymer/GO composites occurring during the typical melt-processing processes, we aim to have a better understanding of the low temperature in situ reduction of GO dispersed in polymer matrices and the influence factors to determine the evolution process of these chemical and physical sturcture of polymer/GO nanocomposites. This study would provide important data and constitute a significant part for the technology of tailoring the structure and properties of graphene-based polymer nanocomposites, and inspire the research and development in this field.

以氧化石墨烯(GO)为起始原料的各类GO基聚合物复合材料因具有各种优异的性能受到广泛关注。但此类材料中GO在熔融加工过程中发生的原位还原反应会导致材料结构、组成发生变化，使有效调控此类材料或制品的结构及性能非常困难。本项目以聚合物/GO复合材料为研究对象，从模压、混炼、挤出等典型熔融加工过程发生的GO原位还原入手，一方面研究决定GO原位还原的各种影响因素及原位还原的可能机理，同时研究因GO原位还原引起材料不同层次聚集态结构及结构演化规律的变化。通过相关研究，较全面地理解此类复合材料熔融加工过程中发生的化学、物理变化，获得影响GO在复合材料熔融加工过程中发生还原反应的各种因素以及GO还原如何影响复合材料结构和性能的新知识，为调控GO基复合材料或制品的组成和结构、形成可控制备特定性能GO基复合材料的新技术提供基础数据。

近年来，以氧化石墨烯(GO)为起始原料的各类聚合物纳米复合材料因广阔的应用潜力受到高度关注。通过熔融法制备此类复合材料，具有无需要使用溶剂、环境友好、成本低、易于规模化生产等优势，但是，在高分子熔融加工过程中GO可能发生的原位还原反应会导致材料的结构、组成发生变化，使得材料性能难以预期。理解GO原位还原的机理及还原对材料性能的影响，是有效调控此类材料或制品结构与性能的基础。本项目以聚合物/GO复合材料为研究对象，从模压、混炼等典型熔融加工过程中GO的原位还原入手，开展了以下四个方面的工作：(1) 从高分子基体的化学结构及剪切等加工条件等方面考察了影响GO在复合材料熔融加工过程中原位还原的因素，对GO在高分子基体中发生原位还原的化学机理有了一定认识；(2) 研究了GO原位还原对材料聚集态结构及性能等方面的影响，获得了一些通过GO的原位还原调控材料性能的新知识；(3)通过引入化学还原剂等方法，探索了基于传统熔融加工技术直接制备还原氧化石墨烯(rGO)复合材料的可能性；(4) 将氧化石墨烯与高分子相结合，设计、制备了多种高性能、功能性材料。通过本项目工作，我们对于高分子/GO复合材料在熔融加工过程中发生的化学物理变化、影响GO发生原位还原反应的主要因素以及GO还原如何影响复合材料的结构和性能等方面，形成较全面的理解。这些数据和认识为调控GO基复合材料的组成和结构、形成可控制备特定性能GO复合材料的新技术具有重要的参考价值。