Wrapping Carbon Nanotubes in Pyrene-Containing Poly(phenylacetylene) Chains:  Solubility, Stability, Light Emission, and Surface Photovoltaic Properties

A group of pyrene-containing poly(phenylacetylene)s (PPAs) with high molecular weight (Mw up to ∼170 000) were synthesized in high yields (up to ∼96%). Simply mixing the polymers and multiwalled carbon nanotubes (MWNTs) in an appropriate solvent afforded the polymer/MWNT hybrids with MWNT contents up to ∼25 wt %, which are soluble in common organic solvents such as chloroform and THF. The solubility can be as high as 637.5 mg/L in THF, thanks to the “additive effect” of the PPA skeleton and the pyrene pendants in solubilizing the MWNTs. The solubilization is realized through the spontaneous wrapping of the polymer chains round the MWNT shells, which is driving by the favorable π−π interactions of the PPA skeleton and the pyrene rings with the MWNT walls. The P2(5)/MWNT hybrid is thermally stable, losing little of its weight when heated to 338 °C. The P2(m)/MWNT hybrids are electronically more conjugated and emit blue-green light more efficiently than their parent polymers upon photoexcitation. The surface photovoltaic cell fabricated from the P2(5)/MWNT hybrid is bipolar, suggesting an efficient photoinduced charge transfer between the two components, i.e., P2(5) and MWNT.