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Organic polymer thermoelectrics (TEs) that can realize direct heat-to-electricity conversion hold great potential in flexible and wearable applications and thus are receiving tremendous attention. Constructing polymer-based nanocomposites represents an effective approach in achieving high TE performance, while current studies on the underlying mechanisms for the improvement of TE properties in aspects of interfacial nanostructures are insufficient. In this work, flexible ternary nanocomposite films with unique interfacial architectures are developed by sequential electrochemical polymerization of conducting polymers and subsequent anion treatment. The optimized interfacial architectures contribute to enhanced π electron conjugation, which facilitates interfacial charge transfer and favours large-area charge transport. The anion treatment further enables the molecular chains to arrange in a more ordered configuration, leading to improved carrier mobility. As a result, the nanocomposites exhibit high power factors of more than 500 μW m−1 K−2 that outperform most of the literature-reported peer composites. The feasible interfacial architecting and anion treatment methods proposed in this study demonstrate high potential in designing high-performance TE nanocomposites.

The design of effective energy systems is crucial for the development of flexible and wearable electronics. Regarding direct converting heat into electricity, thermoelectrochemical cells (TECs) are particularly suitable for low-grade heat harvesting to enable flexible and wearable applications, despite the fact that the electrolyte leakage and complex packaging issues of conventional liquid-based TECs await to be further addressed. Herein, a quasi-solid-state TEC is assembled from polyacrylamide/acidified-single-walled carbon nanotubes (PAAm/a-SWCNTs) composite hydrogel, developed via a facile in situ free-radical polymerization route with tin (IV) chloride/tin (II) chloride (Sn4+/Sn2+) as a redox couple. The as-fabricated TEC with 0.6 wt% a-SWCNTs content presents a large thermoelectrochemical Seebeck coefficient of 1.59 ± 0.07 mV K-1, and exhibits excellent stability in thermoelectrochemical performance against large mechanical stretching and deformation. Owing to this superior stretchability, the as-fabricated TEC is further assembled into an energy-autonomous strain sensor, which shows high sensitivity. The strategy of utilizing quasi-solid-state TEC for energy-autonomous strain sensing unveils the great potential of heat-to-electricity conversion in flexible and wearable electronics.

Polymer thermoelectric (TE) composites have witnessed explosive developments in recent years, arising from their promising prospect for lightweight flexible electronics and capability of harvesting waste-heat. In sharp contrast with intrinsically conducting polymers (CPs), the insulating thermoplastics have seldom been employed as the matrices for flexible TE composites despite their advantages of low costs, controllable melt-flowing behaviors and excellent mechanical properties. Here, we report flexible films of polycarbonate/single-walled carbon nanotube (PC/SWCNT) composites with improved trade-off between TE and mechanical performances. The SWCNTs with 1D nanostructure were dramatically aligned by PC melt-flowing under hot-pressing in the radial direction. The composite maximum power factor reaches 4.8 ± 0.8 μW m−1 K−2 at 10 wt% SWCNTs in the aligned direction, which is higher than most previously reported thermoplastics-based TE composites at the same SWCNT loading and even comparable to some intrinsically CPs and their composites. In addition, these composites display significantly higher tensile modulus and strength than CPs and their composites. This study paves an effective way to fabricate flexible films of polymer composites with simultaneously high TE and mechanical performances via judicious alignment of SWCNTs in thermoplastic polymers.

Although conjugated polymer/carbon nanotube (CNT) thermoelectric (TE) composites have witnessed explosive achievements in recent years, the in-depth mechanism of CNT network evolution and its influence on composite TE performance are still unclear. Herein, we systematically investigate the evolution of single-walled CNT (SWCNT) network structure with a wide SWCNT content range for poly (3,4-ethyienedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/SWCNT composites based on TE properties and atomic force microscopic (AFM) observations. The whole curves of TE performance can be divided into three regions with the increase of SWCNT loading. In Region I (

Processing protocols definitely impact polymer microstructure evolution and thermoelectric (TE) performance; however, in-depth understanding of molecular mechanism is still a challenge. Here, the mechanism of the effects of solution- and melt-processing protocols on polymer microstructure evolution and TE performance has been unraveled, where a semicrystalline poly(3-hexylthiophene) (P3HT) is chosen as a model system. The phase separations between crystallites and amorphous regions are more pronounced for melt-processed films, and solution-processed films display enlarged conjugation length and higher degree of solid-state ordering. In crystalline domains, solution-processed films reveal a completely edge-on structure, while melt-processed exhibit a co-existing of edge-on and face-on crystallites. Additionally, solution-aging strengthens aggregation and phase separation, but has little effect on conjugation length and crystalline texture. Finally, a multiphase semicrystalline model, based on crystalline texture and phase separation, is applied.

An experiment has recently been performed at Xi’an Jiaotong University to study the wall temperature and pressure drop at supercritical pressures with upward flow of water inside a 2×2 rod bundle. A fuel-assembly simulator with four heated rods was installed inside a square channel with rounded corner. The outer diameter of each heated rod is 8 mm with an effective heated length of 600 mm. Experimental parameters covered the pressure of 23–28 MPa, mass flux of 350–1000 kg/m2s and heat flux on the rod surface of 200–1000 kW/m2. According to the experimental data, it was found that the circumferential wall temperature distribution of a heated rod is not uniform. The temperature difference between the maximum and the minimum varies with heat flux and/or mass flux. Heat transfer characteristics of supercritical water in bundle were discussed with respect to various heat fluxes. The effect of heat flux on heat transfer in rod bundles is similar with that in tubes or annuli. In addition, flow resistance reflected in the form of pressure loss has also been studied. Experimental results showed that the total pressure drop increases with bulk enthalpy and mass flux. Four heat transfer correlations developed for supercritical pressures water were compared with the present test data. Predictions of Jackson correlation agrees closely with the experimental data.Copyright © 2014 by ASME