Change in conformation of polymer PFO on addition of multiwall carbon nanotubes.

Multiwall carbon nanotubes (MWNTs) have been added to the polymer poly (9,9-dioctylfluorenyl-2, 7-diyl) end capped with dimethylphenyl (PFO) in various weight percentages and the blends thus prepared, using a solution processing approach, have been characterized using SEM, UV-VIS spectroscopy, PL spectroscopy and I-V characterization. The SEM micrographs show a change in the structure of the polymer from partially crystalline to a glassy state in the blend form. The morphology observations are supported by absorption spectra which show a very high diminution of the polymers' beta peak in the spectra obtained from the polymer-nanotube blend. Thus, multiwall carbon nanotubes modify the local nanoscopic structure of PFO leading to a more glassy structure instead of a partially crystalline form and provide a method to tailor the conformation of polymer PFO, depending on intended application. I-V characteristics reveal an increase in current on formation of the polymer-nanotube blend as compared to the polymer-only structure. On the basis of percolation theory, as applied to these polymer-nanotube blends, a percolation threshold value of 0.45 wt% and critical exponent value of 1.84 has been obtained, indicating the formation of a three dimensional polymer-nanotube network.