Supramolecular Surface Functionalization of Single‐Walled Carbon Nanotubes With Conjugated Graft Copolymers

ABSTRACT

Functionalizing single‐walled carbon nanotubes (SWNTs) without introducing defects on their side walls and altering their optoelectronic properties remains an ongoing challenge. Here, two methodologies are outlined for non‐covalently functionalizing the nanotube surface with bio‐based and biodegradable poly(L‐lactide) chains of varying molecular weight, utilizing the inverse‐electron‐demand Diels‐Alder (IEDDA) reaction and ring‐opening polymerization (ROP). Poly(tetrazine‐co‐fluorene) polymers were synthesized and subsequently reacted with 5‐norbornene‐2‐methanol via IEDDA chemistry. Oxidation of the resulting adducts yielded poly(pyridazine) structures bearing free hydroxyl groups, which served as co‐initiators for the ring‐opening polymerization of L‐lactide. The graft copolymers were used to prepare polymer‐nanotube complexes decorated with polylactic acid chains having molecular weight up to 20 kDa, as confirmed by NMR spectroscopy, thermogravimetric analysis, and atomic force microscopy. Alternatively, poly(pyridazine) bound SWNTs with reactive hydroxyl groups were prepared to polymerize L‐lactide by surface‐initiated ROP through the “grafting from” approach. This method resulted in polylactic acid chains with molecular weights up to 5 kDa without causing any defects to the nanotubes.