Graphene Functionalisation with a Conjugated Poly(fluorene) by Click Coupling: Striking Electronic Properties in Solution

Graphene flakes covalently modified with a conjugated polymer, poly[(9,9-dihexylfluorene)-co-alt-(9,9-bis-(6-azidohexyl)fluorene)] (PFA), were efficiently synthesised by a Cu-catalysed Huisgen 1,3-dipolar cycloaddition between alkyne-modified graphene and an azide-functionalised polymer. Two approaches for the modification of graphene with alkyne groups were investigated (coupling with a diazonium salt generated in situ or an amidation reaction) and the optimum conditions determined. The success of the click-coupling approach was confirmed by FTIR, 1H NMR, Raman, and X-ray photoelectron spectroscopy (XPS). The absorption and emission spectra of the click product show a strong solvent dependency.