Polyurethane(PU) hybrid nanocomposite films containing graphite and multiwalled carbon nanotubes (MWNTs) were prepared by a solution-casting method, and their electrical properties and heating performance were investigated as a function of conducting hybrid filler content. The electrical resistivity of the PU/hybrid nanocomposite films decreased slightly from 2.40×10 2 Ωcm to 2.79×10 1 Ωcm with increasing the hybrid filler content (5.0~9.0 wt%). The current-voltage (I-V) characteristics of these nanocomposite films indicate a significant increase in current level with 9.0 wt% hybrid filler content, which reflects the fact that above the percolation threshold, the conduction mechanism in the nanocomposite films changes from tunneling conduction (nonlinear) to ohmic conduction due to the direct contact between the graphite and the MWNTs (linear). As a result, the PU/hybrid nanocomposite films containing 9.0 wt% hybrid filler with 4.5 wt% graphite and 4.5 wt% MWNTs can be quickly heated from room temperature to 48.8 o C within 80 s by applying a DC voltage of 30 V, whereas the PU nanocomposite films containing 30.0 wt% graphite or 5.0 wt% MWNTs could only be heated to 39.2 o C and 30.6 o C, respectively.

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We synthesized a polyhydroxyamide (PHA) copolymer via low-temperature solution polymerization of 3,3'-dihydroxybenzidine with terephthaloyl chloride (80.0 mol%) and isophthaloyl chloride (20.0 mol%) in N,Ndimethylacetamide with the aid of LiCl. We prepared the PHA copolymer derivatives containing the fluorine-based substituents and investigated their solubility, cyclization behavior, and thermal properties using a differential scanning calorimeter (DSC), a thermogravimetric analyzer (TGA), and the simultaneous thermogravimetric analyzer coupled with a mass spectrometer (STA-MS). The chemical structures of the PHA copolymer and its derivatives, as well as the polybenzoxazoles (PBOs) obtained through thermal cyclization of the copolymer and derivatives, were determined by a fourier transform infrared (FT-IR) spectroscopic analysis. The PHA copolymer could be dissolved in organic solvents only with the aid of LiCl, while its derivatives were readily soluble in DMA c and NMP without LiCl at room temperature. The DSC and TGA results demonstrated that the PHA copolymer derivatives could be converted to PBOs at a lower temperature than the PHA copolymer.

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