Hybrids of Triphenylamine-Functionalized Polyacetylenes and Multiwalled Carbon Nanotubes: High Solubility, Strong Donor−Acceptor Interaction, and Excellent Photoconductivity

Abstract

A group of triphenylamine-functionalized polyacetylenes (TPA-PAs) were synthesized using [Rh(nbd)Cl] 2 as catalyst in high yields (up to 93%). The polymers were characterized by NMR, IR, UV, PL, and CV analyses. The TPA pendants endowed the polymers with desirable redox activity and high photoconductivity. When an electron-withdrawing formyl group was attached to the TPA unit, the resultant polymer (P 3 ) displayed solvatochromism. Simply mixing the polymers with multiwalled carbon nanotubes (MWNTs) in appropriate solvents resulted in the formation of TPA-PA/MWNT hybrids. With the aid of the polymer bearing styryl-TPA pendant (P 2 ), ∼21% of MWNTs were loaded into the hybrid and a solubility of MWNTs in dichloromethane as high as 720 mg/L was achieved, which is among the highest solubilities of MWNTs in organic solvents. The great solvating power of the TPA-PAs for the MWNTs is attributed to the polymer wrapping processes aided by the additive effects of π−π electronic interaction and donor−acceptor (D−A) complexation. This is the first report demonstrating the involvement of D−A interaction in the solubilization of MWNTs by a conjugated polymer. A single-layer photoreceptor with P 3 /MWNT hybrid as charge-generation material displayed a photosensitivity as high as ∼9091 mm 2 /mW·s, which is the highest value recorded for a polyacetylene-based device. The excellent photoconductivity is ascribed to the efficient charge separation in the D−A system and the fast transport of the photogenerated holes and electrons in the polymer and MWNT, respectively.