Poly(9,9′-diheylfluorene carbazole) Functionalized with Reduced Graphene Oxide: Convenient Synthesis using Nitrogen-Based Nucleophiles and Potential Applications in Optical Limiting

Covalently functionalized reduced graphene oxide (RGO) sheet was prepared by treating nitrogen‐centered anions generated from poly(9,9′‐diheylfluorene carbazole) (PCF) with GO. The resultant hybrids with different chemical behavior were separated by centrifugation. The covalent modification was fully characterized by IR spectroscopy, UV/Vis spectroscopy, thermogravimetric analysis (TGA), Raman spectroscopy, TEM, and SEM. It was found that RGO‐PCF‐s, the soluble part, was split into small platelets with a size of about 200 nm, and the hydrophobic polymer PCF became hydrophilic after wrapping by RGO. The content of RGO in RGO‐PCF‐s was about 11.9 %, and the hybrid material showed good dispersion stability in water. Besides, RGO‐PCF‐i, the insoluble part, with larger size, displayed excellent optical‐limiting response, in which both nonlinear absorption and nonlinear scattering play important roles. As nitrogen‐centered anions are an important type of intermediates in chemistry, this one‐step “grafting‐to” strategy could be used to obtain RGO‐based materials with different applications. Graphene modification: A nucleophilic reaction between graphene oxide and poly(9,9′‐diheylfluorene carbazole) leads to a chemically modified reduced graphene oxide sheet (see scheme). Other products with different size and solubility could be separated by simple centrifugation. The soluble part showed good solubility in water, while the insoluble part displayed good optical‐limiting response.