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Abstract
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Reduced graphene oxide (rGO) is functionalized with 2-thiophene acetic acid (rGO-f-TAA) and grafted with poly(3-dodecylthiophene) (rGO-g-PDDT) and poly(3-thiophene ethanol) (rGO-g-PTEt) to manipulate the orientation and patterning of crystallized poly(3-hexylthiophene) (P3HT). P3HT chains prefer to interact with their thiophene rings with bared rGO surface, resulting in a conventional face-on orientation. In these hybrids, beyond critical length of P3HT nanofibers developed onto rGO (>100 nm), an inclination occurs after solvent evaporation, thereby face-on noninclined fibers change to edge-on inclined ones. In P3HT/rGO-f-TAA supramolecular structures patterned with P3HT short nanofibrils (42–95 nm in length), the orientation of P3HT chains changes from face-on to edge-on, originating from strong interactions between hexyl side chains of P3HTs and 2-thiophene acetic acid functional groups of rGO. Supramolecular structures based on grafted rGO demonstrate a patched-like morphology composed of flat-on P3HTs with main backbones perpendicular to substrate. Grafted polythiophenic oligomers onto rGO (rGO-g-PDDT and rGO-g-PTEt) provoke P3HT backbones to vertically attach to surface and remain perpendicular even after solvent evaporation. Flat-on orientation acquired for rGO-g-PDDT and rGO-g-PTEt systems is the best for P3HT chains assembled onto rGO. Face-on P3HT/rGO hybrids and, subsequently, edge-on P3HT/rGO-f-TAA hybrids also reflect optical and supramolecular donor–acceptor properties based on ultraviolet–visible and photoluminescence analyses.
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