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

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 (P3) 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 (P2), similar to 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 pi-pi 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 P3/MWNT hybrid as charge-generation material displayed a photosensitivity as high as similar to 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.