Polymer wrapping versus well-oriented crystal growth of polythiophenes onto multi-wall carbon nanotubes via surface chemical modification and regioregularity deliberation

Abstract

Wrapped multi-walled carbon nanotubes (CNTs) with regiorandom poly(3-dodecyl thiophene) (RRa-PDDT) chains with no traces of ordering in electron diffraction and grazing incidence scattering patterns were developed using RRa-PDDT and CNTs. In these supramolecules, there was no difference between bare (BCNT), functionalized with a thiophenic adduct (CNT-f-COOTh), and grafted (CNT-g-PDDT) carbon nanotubes for wrapping and only the PDDT : CNT ratio was effective. By replacing the RRa-PDDT chains with regioregular poly(3-hexyl thiophene) (RR-P3HT), distinct hybrids including double-fibrillar, shish–kebab, shish–kebab–shish, stem–leaf and stem–leaf–stem were developed. The most effective parameter on the morphology of the donor–acceptor supramolecules based on RR-P3HTs was surface functionalization and grafting. The RR-P3HT chains interacted through their thiophenic rings with the surface of BCNTs, and thereby a face-on orientation was developed for the stacking of P3HT chains onto the CNT surfaces. By functionalization of the CNT surface (FCNT), shish (CNT)–kebab (RR-P3HT) and shish (CNT)–kebab (RR-P3HT)–shish (RR-P3HT) supramolecules were originated for high density (HD = 62%) and low density (LD = 28%) functionalizations, respectively. When the surface of the CNTs was grafted with PDDT (GCNTs), stem (CNT)–leaf (RR-P3HT) and stem (CNT)–leaf (RR-P3HT)–stem (RR-P3HT) configurations were detected for HD and LD GCNTs, respectively. Thanks to the flat-on oriented P3HTs, the best photoluminescence quenching, and thereby the best donating–accepting features were detected for the HD/LD CNT-g-PDDT supramolecules.