The thermoelectric properties of carbon nanotube (CNT)-filled polymer composites can be enhanced by modifying junctions between CNTs using poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), yielding high electrical conductivities (up to approximately 40000 S/m) without significantly altering thermopower (or Seebeck coefficient). This is because PEDOT:PSS particles are decorated on the surface of CNTs, electrically connecting junctions between CNTs. On the other hand, thermal transport remains comparable to typical polymeric materials due to the dissimilar bonding and vibrational spectra between CNT and PEDOT:PSS. This behavior is very different from that of typical semiconductors whose thermoelectric properties are strongly correlated. The decoupled thermoelectric properties, which is ideal for developing better thermoelectric materials, are believed to be due to thermally disconnected and electrically connected contact junctions between CNTs. Carrier transport at the junction is found to be strongly dependent on the type and concentration of stabilizers. The crucial role of stabilizers was revealed by characterizing transport characteristics of composites synthesized by electrically conducting PEDOT:PSS and insulating gum Arabic (GA) with 1:1-1:4 weight ratios of CNT to stabilizers. The influence of composite synthesis temperature and CNT-type and concentration on thermoelectric properties has also been studied. Single-walled (SW) CNT-filled composites dried at room temperature followed by 80 degrees C exhibited the best thermoelectric performance in this study. The highest thermoelectric figure of merit (ZT) in this study is estimated to be approximately 0.02 at room temperature, which is at least one order of magnitude higher than most polymers and higher than that of bulk Si. Further studies with various polymers and nanoparticles with high thermoelectric performance may result in economical, lightweight, and efficient polymer thermoelectric materials.

Segregated-network carbon nanotube (CNT)-polymer composites were prepared, and their thermoelectric properties were measured as a function of CNT concentration at room temperature. This study shows that electrical conductivity can be dramatically increased by creating a network of CNTs in the composite, while the thermal conductivity and thermopower remain relatively insensitive to the filler concentration. This behavior results from thermally disconnected, but electrically connected, junctions in the nanotube network, which makes it feasible to tune the properties in favor of a higher thermoelectric figure of merit. With a CNT concentration of 20 wt %, these composites exhibit an electrical conductivity of 4800 S/m, thermal conductivity of 0.34 W/m x K and a thermoelectric figure of merit (ZT) greater than 0.006 at room temperature. This study suggests that polymeric thermoelectrics are possible and provides the basis for further development of lightweight, low-cost, and nontoxic polymer composites for thermoelectric applications in the future.

Page 4429. The sentence that starts at the bottom of the left column that reads "XD grade CNTs (Carbon Nanotechnologies, Inc.), which are a mixture of metallic and semiconducting single-, double-, and triple-walled CNTs, were incorporated in the matrix." should be changed into the following new sentence: "Purified HIPCO single-walled carbon nanotubes (Carbon Nanotechnologies, Inc.), with 5 wt % residual Fe impurity, were incorporated into the matrix."

The influence of the stabilizer/SWNT ratio on the transport behavior of latex‐based polymer nanocomposites is examined in an effort to improve electrical conductivity while maintaining or improving the Seebeck coefficient (i.e., thermopower). Results show that phonon and electron transport are significantly affected by tube/tube junctions, and the carrier transport across the junctions can be manipulated by altering the stabilizer concentration. Electrical conductivity of composites containing 10 wt.‐% SWNT nearly doubles, becoming greater than 900 S · m−1, by changing the SWNT:GA ratio from 1:3 to 10:1, while thermal conductivity and Seebeck coefficient remain relatively constant (near 0.25 W · m‐K−1 and 40 µV · K−1, respectively).

Carbon nanotube (CNT)-polymer composites were prepared by segregated network approach. CNTs were served as conductive fillers in a polymer matrix to synthesize electrically conducting polymer composites. In the segregated network composites, the thermoelectric properties were further improved by replacing Gum Arabic (GA) with electrically conductive stabilizer PEDOT:PSS doped with dimethyl sulfoxide (DMSO). The electrical and thermal conductivities and Seebeck coefficient were measured to determine the thermoelectric property of the polymer composites. The electrical conductivity of the composites with 9.8wt% of CNT was 3191.8 S/m whereas that of 10wt% CNT composite with GA sample was 400 S/m.