Multiwalled carbon nanotubes (MWNTs) and ultrahigh molecular weight polyethylene (UHMWPE) composites were prepared by gelation/crystallization from solution. The dried composites of MWNTs−UHMWPE with 15 wt % of MWNTs would be elongated up to more than 100-fold (λ = 100). The electric conductivity was 10-3 S/cm termed as conductive materials, and the Young's modulus reached 58 GPa at room temperature. The composites possess extraordinary stability in electric conductivity during many repeated heating cycles from room temperature to 150 °C. Scanning electron microscopy revealed that MWNTs with continuous networks are oriented predominantly parallel to the stretching direction. Such characteristic alignment of MWNTs was found to play an important role in forming effective conductive paths in the highly oriented composites.

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Thermally sensitive poly(N-isopropylacrylamide) (PNIPAM) spherical microgels with different charge distribution were prepared by different monomer and comonomer feeding methods. The frequency ( f, 10 −2 −10 7 Hz) and temperature (T, 5−50 °C) dependent complex dielectric/electric properties of these microgels were analyzed by dielectric relaxation spectroscopy. Each microgel can be treated as a large multicharged macroion surrounded by many small counterions, and the relative displacement and the diffusion of counterions contribute to the permittivity and conductivity of the microgel dispersion. Both the dielectric permittivity at f > 10 3 Hz and the conductivity at f > 10 6 Hz decrease when the microgels shrink at temperatures higher than the lower critical solution temperature (LCST) of PNIPAM due to the shrink-induced counterion dissociation. The variation of either permittivity or conductivity with temperature reveals a sharper transition for the microgels or the microgel shell with a more uniform charge distribution than those with an inhomogeneous dense core−loose shell structure, indicating a more gradual chain shrinkage for the latter. By detecting the counterions' behaviors, we can use dielectric relaxation spectroscopy to probe the microscopic structural and dynamic heterogeneities of PNIPAM microgel dispersions.