(Invited) Photoinduced Charge Transfer Reactions in Chiral, Semiconducting Polymer-Wrapped Single-Walled Carbon Nanotube Superstructures

Abstract

Highly charged, chiral anionic semiconducting polymers helically wrap single-walled carbon nanontubes (SWNTs) at periodic and constant morphology. These polymers can be used as tools to modulate SWNT electronic properties, provide expansive solubility, or engineer electron acceptor units at rigorously defined intervals along the nanotube backbone. We detail (SWNT)-based nanohybrid compositions based on (6,5) chirality-enriched SWNTs ([(6,5) SWNTs]) and chiral n-type polymers such as (S-PBN(b)-Ph4PDI), that feature a perylenediimide (PDI)-containing repeat unit; S-PBN(b)-Ph4PDI-[(6,5) SWNT] superstructures, for example, feature a PDI electron acceptor unit positioned at 3 nm intervals along the nanotube surface, thus controlling rigorously SWNT–electron acceptor stoichiometry and organization. Potentiometric studies determine driving forces for photoinduced charge separation (CS) and thermal charge recombination (CR) reactions, as well as spectroscopic signatures of SWNT hole polaron and PDI radical anion states. Femtosecond pump-probe transient absorption spectroscopic experiments show that excitation into the SWNT E11 transition of a S-PBN(b)-Ph4PDI-[(6,5) SWNT] superstructure generates SWNT hole polaron [(6,5) SWNT(•+)n] and PDI radical anion (PDI−•) states. Here we describe related compositions that detail reaction driving force- and solvent-dependent photoinduced CS and thermal CR reactions, and provide insights into the factors that govern photoinduced charge transfer reactions at soft matter-hard matter interfaces defined by polymers and SWNTs. Figure 1