Composites of Functional Poly(phenylacetylene)s and Single-Walled Carbon Nanotubes: Preparation, Dispersion, and Near Infrared Photoresponsive Properties

To explore poly(phenylacetylene) (PPA) derivatives as the dispersing agent of single-walled carbon nanotubes (SWNTs), we synthesized a new series of side chain PPAs (denoted as PPA- m, m = 2, 1, 0). The side chains of PPA- m bear a soluble 3,4,5-tris(octyloxy)phenyl moiety at the end, and a biphenyl ( m = 2), a phenyl ( m = 1), or no phenyl ring ( m = 0) in the middle linked to the PPA main-chain through an ether linkage. All the three PPA- m s can efficiently disperse SWNTs in organic solvents forming stable SWNTs/PPA- m composites. The composites were characterized by microscopy method, absorbance and photoluminescence spectroscopy. Quantitative analysis shows that there is a tendency for PPA- m to preferentially disperse SWNTs with large diameters in tetrahydrofuran and toluene when compared with the normally used surfactant of sodium dodecyl sulfate. The effective interactions between PPA- m and SWNTs should be ascribed to the helical wrapping of the PPA- m backbone on SWNTs and the π–π interactions between the phenyl groups and SWNTs. The long alkyl tails on the side-chains also prevent individual SWNTs from reaggregation. Additionally, the near-infrared (nIR) photoresponsive electrical conductivity of the SWNTs/PPA-2 composite is measured, indicating a 12% increase of the photocurrent upon the nIR irradiation, which is greater compared with that of the reported pure SWNTs film.