Covalent Functionalization Of Graphene Nanosheets With Polymers

Graphene has become a new hotspot after carbon tube since its discovery in2004, due to its unique structure and excellent physical and chemical properties. Graphene, however, tends to aggregate to form three dimensional graphite with poor solubility in regular solvents, for graphene sheets have strong ultra-molecular force, including Van der Waals force and π-π interaction, which limits its further applications. Therefore, it is meaningful to improve its solubility and dispersibility in solvents.Polymers are very good candidates among those modifiers for graphene, because polymer brushes not only assist to improve the solubility of graphene derivatives, but offer additional functionality to the resulting hybrid nanosheets. It is very convenient to combine the control/living polymerization methods with efficient coupling reactions for the preparation of graphene/polymer nanocomposites. Covalent attachment of polymer chains onto the surface of graphene can be achieved by the "grafting-onto" and "grafting-from" strategies. In this work, we prepared several graphene/polymer composites based on the above-mentioned two strategies. The details were as follows:(1) PIB-functionalized graphene was prepared by combining cationic polymerization with ATNRC/SET-NRC coupling methods via the "grafting-onto" strategy. The resulting product was characterized in detail to make sure the covalent bonding between PIB and graphene. In addition, we compared two different coupling methods, ATNRC and SET-NRC, in various aspects, and we found that SET-NRC was a more efficient, economic and easier method in comparison with ATNRC.(2) PHPMA-functionalized graphene was prepared by combining RAFT polymerization with click chemistry via the "grafting-onto" strategy. The resulting product was well characterized and we found that PHPMA-functionalized graphene had better solubility in regular solvents.(3) We utilized SET-LRP method to prepare PHEA-functionalized graphene by initiating SET-LRP of HEA monomer from the surface of graphene via the "grafting-from" strategy. The resulting product revealed that the composites had better solubility in organic solvents.