Enhanced Thermoelectric Performance of PEDOT:PSS Films by Sequential Post‐Treatment with Formamide

This paper reports a series of sequential post‐treatments using a polar solvent formamide to enhance the thermoelectric performance of poly(3,4‐ethylenedioxythiophene) doped with poly(styrene sulfonate) anions (PEDOT:PSS). The electrical conductivity of PEDOT:PSS films significantly increases from 0.33 S cm^?1 for the pristine film to ≈2929 S cm^?1 for the treated film and meanwhile the Seebeck coefficient maintains as high as 17.4 µV K^?1, resulting in a power factor of 88.7 µW m^?1 K^?2. Formamide is a polar solvent with a high boiling point of 210 °C and high dielectric constant of 109, and PSS has a good solubility in it. Post‐treatment with formamide causes not only the phase segregation of PEDOT and PSS but also the removal of insulating PSS, therefore leading to the reorientation of PEDOT chains and enhancement in mobility without altering the doping level considerably. The cross‐plane thermal conductivity also reduces from 0.54 to 0.19 W m^?1 K^?1 after the post‐treatment, leading to a figure of merit (ZT) value of 0.04 at room temperature.     

Chemically bonded iron carbonyl for magnetic composites based on phthalonitrile polymers

Dicarboxylic acid‐containing 1,3‐benzoxazine was synthesized and chemically bonded on iron carbonyl particles using a post‐coating method. Novel organic–inorganic hybrid magnetic composites were prepared via the interfacial reaction between magnetic phthalonitrile prepolymers and the benzoxazine functional coatings that chemically modified the iron carbonyl particles. The results showed that, compared with pure iron carbonyl particles, the modified particles could cure the phthalonitrile prepolymers efficiently and improve the interfacial compatibility of the functional composites. The magnetic composites with chemically modified particles exhibited stronger magnetism in comparison to composites containing bare particles: the saturation magnetization of the magnetic composites with equal concentration (5 wt%) of Fe(CO)₅ increased from 41.12 to 48.82 emu g^?1. Also, the magnetic composites obtained demonstrated excellent thermal stability up to 500 °C. Copyright © 2010 Society of Chemical Industry     

Aluminum nitride‐single walled carbon nanotube nanocomposite with superior electrical and thermal conductivities

Development of aluminum nitride (AlN)‐single walled carbon nanotube (SWCNT) ceramic‐matrix composite containing 1‐6 vol% SWCNT by hot pressing has been reported in this article. The composites containing 6 vol% SWCNT are dense (~99% relative density) and show high dc electrical conductivity (200 Sm^?1) and thermal conductivity (62 Wm^?1K^?1) at room temperature. SWCNTs contain mostly metallic variety tubes obtained by controlled processing of the pristine tubes before incorporation into the ceramic matrix. Raman spectroscopy and field emission scanning electron microscopy (FESEM) of the fracture surface of the samples show the excellent survivability of the SWCNTs even after high‐temperature hot pressing. The results indicate the possibility of preparation of AlN nanocomposite for use in plasma devices and electromagnetic shielding.     

Enhanced thermoelectric performance of poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) with long‐term humidity stability via sequential treatment with trifluoroacetic acid

This paper reports a range of effective sequential chemical processes to enhance the thermoelectric performance of conducting poly(3,4‐ethylenedioxythiophene) films doped with poly(styrene sulfonate) anions (PEDOT:PSS). The electrical conductivity of the PEDOT:PSS films was significantly increased from 0.33 to 3748 S cm^?1 after a series of sequential treatments with trifluoroacetic acid (TFA) while the Seebeck coefficient and thermal conductivity were slightly reduced from 17.5 ± 1.2 to 16.0 ± 1.1 μV K^?1 and 0.537 to 0.415 W m^–1 K^?1 for the pristine film and treated film, respectively, leading to a significant improvement in power factor up to 97.1 ± 5.4 μW m^–1 K^?2. More importantly, around 80% of the electrical conductivity and Seebeck coefficient was retained after 20 days for these TFA‐treated PEDOT:PSS films, revealing the potential for real thermoelectric applications. © 2019 Society of Chemical Industry     

Microwave‐assisted in situ polymerization of polycaprolactone/boron nitride composites with enhanced thermal conductivity and mechanical properties

Polycaprolactone/boron nitride (PCL/BN) composites were prepared by microwave‐assisted ring‐opening polymerization of ε‐caprolactone (ε‐CL). In order to improve the dispersibility and interfacial interaction between BN fillers and PCL matrix, hydroxyl functional BN (mBN) was first prepared to be used as a macroinitiator for ε‐CL. Then BN grafted PCL (BN‐g‐PCL) copolymers were obtained via the in situ method, which acted as in situ compatibilizers in the PCL/BN composites. Various techniques were applied to characterize the mBN and PCL/BN composites. The Fourier transform infrared spectroscopy results confirm the structure of the BN‐g‐PCL copolymer. Field emission SEM graphs exhibit that, for the PCL/mBN composites, the mBN presents a homogeneous dispersion in the matrix and interfacial adhesion between the PCL and mBN is improved. These are beneficial for enhancing the thermal conductivity of the PCL/mBN composites. Notably, the PCL/mBN composite with 5 wt% mBN loading achieves the highest thermal conductivity of 0.55 W m^?1 K^?1, which is 2.75 times higher than that of pure PCL, 0.20 W m^?1 K^?1. This indicates that the excellent dispersion and interfacial adhesion could lead to the construction of continuous thermal conductive paths at a low BN loading and reduce the heat loss caused by phonon scattering in the interface. Furthermore, mBN could help to improve the mechanical properties of the composite. On adding 5 wt% mBN, the tensile strength and tensile modulus of the composite are 1.58 and 2.05 times higher, respectively, than those of PCL. © 2020 Society of Chemical Industry     

Robust PEDOT:PSS Wet‐Spun Fibers for Thermoelectric Textiles

To realize thermoelectric textiles that can convert body heat to electricity, fibers with excellent mechanical and thermoelectric properties are needed. Although poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is among the most promising organic thermoelectric materials, reports that explore its use for thermoelectric fibers are all but absent. Herein, the mechanical and thermoelectric properties of wet‐spun PEDOT:PSS fibers are reported, and their use in energy‐harvesting textiles is discussed. Wet‐spinning into sulfuric acid results in water‐stable semicrystalline fibers with a Young's modulus of up to 1.9 GPa, an electrical conductivity of 830 S cm^?1, and a thermoelectric power factor of 30 μV m^?1 K^?2. Stretching beyond the yield point as well as repeated tensile deformation and bending leave the electrical properties of these fibers almost unaffected. The mechanical robustness/durability and excellent underwater stability of semicrystalline PEDOT:PSS fibers, combined with a promising thermoelectric performance, opens up their use in practical energy‐harvesting textiles, as illustrated by an embroidered thermoelectric fabric module.     

Effect of graphite on the power density of selenium doped polyaniline ink based hybrid screen-printed flexible thermoelectric generator

Enhancement in the thermoelectric performance of inorganic/organic hybrid composites and the need for low-cost, flexible thermoelectric generators have motivated this work. The thermoelectric effect on the addition of amorphous polyaniline, crystalline selenium, and layer-structured graphite, with different concentrations on the thermoelectric properties of selenium-doped polyaniline, is reported. Tuning of microstrain, dislocation density, and carrier concentration has improved the Seebeck coefficient by 39.10% and electrical conductivity by 60.22%. The maximum power output and power factor exhibited by the hybrid device are 1.89 nW and 0.42 nW/m²K² at a temperature difference of 100 °C. Replacing 90 wt% of Selenium-doped polyaniline with graphite resulted in a power density of 0.65 mW/m² under external load conditions.     

Ultralight and Low Thermal Conductivity Polyimide–Polyhedral Oligomeric Silsesquioxanes Aerogels

The research on rapid growing, organic, and ultralight cross‐linking polyimide aerogels is receiving significant interest. In this work, poly(aminophenyl) silsesquioxanes (PAPSQ) are introduced as a cross‐linker into the polymide (PI) aerogel. A comparative aerogel is prepared, using 1,3,5‐triaminophenoxybenzene (TAB) as a cross‐linker. The aerogels are characterized in terms of their micro‐ and nanostructures, density, shrinkage, thermal conductivity and insulation, and mechanical properties. It is found that the PI‐PAPSQ aerogel have lower density, smaller shrinkage, lower thermal conductivity, higher thermal stability and insulation, and higher compression strength than the PI‐TAB aerogel. The 1.1 wt% PI‐PAPSQ shows the lowest aerogel density (0.010 g cm^?3) and the 2.2 wt% PI‐PAPSQ has a lower thermal conductivity (22.90 mW (m K)^?1 than air. A model of the PI‐TAB and PI‐PAPSQ cross‐linking networks are proposed to explain the excellent performance of the PI‐PAPSQ aerogel.     

Simultaneously enhanced mechanical properties and thermal properties of ultrahigh‐molecular‐weight polyethylene with polydopamine‐coated α‐alumina platelets

Polydopamine (PDA) was employed to modify micrometric Al₂O₃ platelets to improve the interfacial compatibility between α‐Al₂O₃ powder and ultrahigh‐molecular‐weight polyethylene (UHMWPE). The structure of PDA‐coated Al₂O₃ and UHMWPE composites was investigated via Fourier transform infrared spectroscopy, scanning electron microscopy and X‐ray photoelectron spectroscopy. The thermal stability and mechanical performance of the samples were also evaluated. It is clear that UHMWPE/PDA‐Al₂O₃ composites exhibit better mechanical properties, higher thermal stability and higher thermal conductivity than UHMWPE/Al₂O₃ composites, owing to the good dispersion of Al₂O₃ powder in the UHMWPE matrix and the strong interfacial force between the macromolecules and the inorganic filler caused by the presence of PDA. The tensile strength and the tensile elongation at break of UHMWPE/PDA‐Al₂O₃ composite with 1 wt% PDA‐Al₂O₃ are 62.508 MPa and 462%, which are 1.96 and 1.98 times higher than those of pure UHMWPE, respectively. The thermal conductivity of UHMWPE/PDA‐Al₂O₃ composite increases from 0.38 to 0.52 W m^?1 K^?1 with an increase in the dosage of PDA‐Al₂O₃ to 20 wt%. The results show that the prepared PDA‐coated Al₂O₃ powder can simultaneously enhance the mechanical properties and thermal conductivity of UHMWPE. © 2018 Society of Chemical Industry     

Ionically Cross‐Linked Proton Conducting Membranes for Fuel Cells

For improving stability without sacrificing ionic conductivity, ionically cross‐linked proton conducting membranes are fabricated from Na⁺‐form sulfonated poly(phthalazinone ether sulfone kentone) (SPPESK) and H⁺‐formed sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO). Ionically acid‐base cross‐linking between sulfonic acid groups in SPPO and phthalazone groups in SPPESK impart the composite membranes the good miscibility and electrochemical performance. In particular, the composite membranes possess proton conductivity of 60–110 mS cm⁻¹ at 30 °C. By controlling the protonation degree of SPPO within 40–100 %, the composite membranes with favorable cross‐linking degree are qualified for application in fuel cells. The maximum power density of the composite membrane reaches approximately 1100 mW cm⁻² at the current density of 2800 mA cm⁻² at 70 °C.     

Ice‐Templated Poly(vinyl alcohol): Enhanced Strength and Low Thermal Conductivity

The freeze‐casting technique has been used for a variety of materials to tailor their pore structure. The growing ice crystals act as a template for the subsequent voids present in the body. While it is mostly used for inorganic oxide materials, the method is also applicable to polymers like poly(vinyl alcohol) (PVA). The synthesized materials have an aligned anisotropic pore structure which significantly influences the mechanical behavior and the thermal conductivity. Glutaraldehyde (GA) can be used as a cross‐linking agent to reduce the water solubility of the PVA samples. The composition‐dependent thermal conductivities are measured, and found to be 0.055–0.078 W m^?1 K^?1 parallel to the freezing direction and 0.048–0.058 W m^?1 K^?1 in the transverse direction. The scaffold‐like structure resembling the hydroxyapatite structures in bones yields high strength values in the axial direction well exceeding that of common unsupported building insulation materials.     

A conductive foam: Based on novel poly(styrene‐b‐butadiene‐co‐styrene‐b‐styrene) tri‐block copolymer filled by carbon black

In this article, a conductive foam based on a novel styrene‐based thermoplastic elastomer called poly(styrene‐b‐butadiene‐co‐styrene‐b‐styrene) tri‐block copolymer S(BS)S was prepared and introduced. S(BS)S was particularly designed for chemical foaming with uniform fine cells, which overcame the shortcomings of traditional poly(styrene‐b‐butadiene‐b‐styrene) tri‐block copolymer (SBS). The preparation of conductive foams filled by the carbon black was studied. After the detail investigation of cross‐linking and foaming behaviors using moving die rheometer, the optimal foaming temperature was determined at 180°C with a complex accelerator for foaming agent. Scanning electron microscopy (SEM) images shown that the cell bubbles of conductive foam were around 30–50 µm. The conductivity of foams was tested using a megger and a semiconductor performance tester. SEM images also indicated that the conductivity of foams was mainly affected by the distribution of carbon black in the cell walls. The formation of the network of the carbon black aggregates had a contribution to perfect conductive paths. It also found that the conductivity of foams declined obviously with the foaming agent content increasing. The more foaming agent led to a sharp increasing of the number of cells (from 2.93 × 10⁶ to 6.20 × 10⁷ cells/cm³) and a rapid thinning of the cell walls (from 45.3 to 1.4 µm), resulting in an effective conductive path of the carbon black no forming. The conductive soft foams with the density of 0.48–0.09 g/cm³ and the volume resistivity of 3.1 × 10³?2.5 × 10⁵ Ω cm can be easily prepared in this study. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41644.     

Cross‐linked Poly(arylene ether ketone) Proton Exchange Membranes with High Ion Exchange Capacity for Fuel Cells

Sulfonated poly(arylene ether ketone) (SPAEK) possessing the pendant carboxylic acid groups was synthesized. The carboxylic acid groups of SPAEK were reacted with a cross‐linking reagent to prepare a cross‐linked membrane with a high ion exchange capacity (IEC), a high oxidative stability, and an excellent mechanical strength. The cross‐linking hindered the mobility of the polymer chains and thus strongly affected the water uptake and the methanol permeability of the membranes. Also, as the cross‐linker used in this study bore sulfonic acid groups, cross‐linking did not lead to a noticeable loss of the proton conductivity. The cross‐linked SPAEK membrane with 20% cross‐linking density, CSPAEK‐20% membrane, exhibited a high proton conductivity of 0.045 S cm^–1 associated with a high IEC value of 1.78 mmol g^–1 but a low methanol permeability of 4.3 × 10^–7 cm² s^–1. The CSPAEK‐20% membrane also showed excellent cell performance and oxidation resistance.     

In situ sol–gel route to novel sulfonated polyimide?SiO2 hybrid proton‐exchange membranes for direct methanol fuel cells

Polyimides (PIs) as high‐performance organic matrices are used in the preparation of PI composites because of their excellent mechanical, thermal and dielectric properties. The sol–gel method is a promising technique for preparing these PI composites due to the mild reaction conditions and the process being controllable. Although sulfonated polyimide (SPI) proton‐exchange membranes have attracted much attention recently, studies on preparing SPI‐based hybrid proton‐exchange membranes for fuel cells have been rare. A series of SPI? SiO₂ hybrid proton‐exchange membranes were prepared from amino‐terminated SPI pre‐polymers, 3‐glycidoxypropyltrimethoxysilane (KH‐560) and tetraethylorthosilicate through a co‐hydrolysis and condensation process using an in situ sol–gel method. The reactive silane KH‐560 was used to react with amino‐terminated SPI to form silane‐capped SPI in order to improve the compatibility between the polymer matrix and the inorganic SiO₂ phase. The microstructure and mechanical, thermal and proton conduction properties were studied in detail. The hybrid membranes were highly uniform without phase separation up to 30 wt% SiO₂. The storage modulus and tensile strength of the hybrid membranes increased with increasing SiO₂ content. The introduction of SiO₂ improved the methanol resistance while retaining good proton conductivity. The hybrid membrane with 30 wt% SiO₂ exhibited a proton conductivity of 10.57 mS cm^?1 at 80 °C and methanol permeability of 2.3 × 10^?6 cm² s^?1 possibly because the crosslinking structure and SiO₂ phases formed in the hybrids could retain water and were helpful to proton transport. Copyright © 2010 Society of Chemical Industry     

Ionomer covalent functionalization of single‐walled carbon nanotubes by radical polymerization of zirconium acrylate

A facile and efficient covalent functionalization of single‐walled carbon nanotubes (SWCNTs) via peroxide‐mediated free radical covalent attachment and polymerization of zirconium acrylate is reported. The resulting covalently functionalized SWCNTs exhibit improved solubility in organic solvents. The covalently functionalized SWCNTs are characterized by cross polarization magic angle spinning ¹³C NMR, differential scanning calorimetry, thermogravimetric analysis, x‐ray diffraction, Raman, and infrared spectroscopy. Infrared spectroscopy reveals that carboxylate groups of covalently attached ionomers chelate with zirconium ions and the participating carboxylate groups may be from different ionomer chains leading to cross‐linking the chains. The SWCNT topology, ionic clustering, and π‐electron clouds were explored by transmission electron microscopy. © 2014 American Institute of Chemical Engineers AIChE J, 60: 820–828, 2014     

Preparation and thermal effects of polyarylene ether nitrile aluminium nitride composites

Particulate‐filled polyarylene ether nitrile (PEN) composites were prepared using methyltriethoxy‐silane‐treated aluminium nitride (AlN) as the filler for thermal modification. The effects of AlN fraction, particle size and surface treatment on the thermal performance of PEN were investigated. The thermal conductivities of the composites increased when the AlN filler concentration was increased, as well as with decrement of the filler size. The thermal conductivity value of the composites increased up to 0.779 W m^?1 K^?1 when the AlN weight loading was 60 wt%. The trend of the thermal conductivities of the composites can be more efficiently predicted by theoretical models than empirical models. The composites exhibited stable performances of thermal decomposition and thermal expansion when AlN filler faction in the composites increased. © 2013 Society of Chemical Industry     

Interfacial synthesis of polypyrrole/graphene composites and investigation of their optical,electrical and electrochemical properties

We report the development of a novel route for the synthesis of polypyrrole/graphene (PPy/GR) composites by liquid ? liquid interfacial polymerization, where GR and the initiator were dispersed in the aqueous phase and the monomer was dissolved in the organic phase. The synthesized samples were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, Raman spectroscopy, X‐ray diffraction, thermogravimetric analysis, electrochemical and electrical conductivity measurements. Structural analysis reveals a uniform dispersion of GR sheets in the PPy matrix. The composites showed noticeable improvement in thermal stability and electrical conductivity (8.45 S cm^?1) and excellent electrochemical reversibility in comparison with pure PPy. A specific capacitance of 260 F g^?1 at a current density of 100 mA g^?1 was achieved for the composite during the charge–discharge process. © 2013 Society of Chemical Industry     

In situ preparation of polyaniline within neutral,anionic, and cationic superporous cryogel networks as conductive,semi‐interpenetrating polymer network cryogel composite systems

Polyaniline [p(An)], one of the most known conducting polymers, was prepared within superporus nonionic polyacrylamide [p(AAm)], anionic poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid sodium salt) [p(AMPS)], and cationic poly(3‐acrylamidopropyltrimethyl ammonium chloride) [p(APTMACl)] cryogels. After they were synthesized, washed, and dried, the neutral p(AAm), anionic p(AMPS), and cationic p(APTMACl) cryogels were soaked in an ammonium persulfate/aniline solution (1:1.25 ratio) in 1 M hydrochloric acid for the in situ oxidative polymerization of p(An) with the cryogel matrices as templates or reactors. The prepared p(AAm)/p(An), p(AMPS)/p(An), and p(APTMACl)/p(An) semi‐interpenetrating polymer network (semi‐IPN) conductive cryogel composites were characterized with scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and conductivity analysis. The SEM images revealed that the superporus cryogel networks were almost completely filled with p(An) conductive polymers (CPs). Among the cryogel–CP semi‐IPNs, we found that p(AAm)/p(An) semi‐IPN conductive cryogel composites provided the highest conductivity values of 1.4 × 10^?2 ± 4 × 10^?4 S/cm; this was a 6.4 × 10⁶ fold increase in the conductivity from the values of 2.2 × 10^?9 ± 1 × 10^?10 for p(AAm) cryogels. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44137.     

Thermal Insulation Characteristics of Polybenzoxazine Aerogels

Polybenzoxazine (PBO) aerogels with low densities and low thermal conductivities are prepared from Bisphenol A (BPA) benzoxazine monomers by ring‐opened polymerisation using HCl as a catalyser at 10 °C. The obtained PBO aerogels have cross‐linked and 3D network structures with the densities ranging from 0.084 to 0.526 g cm^?3. The thermal conductivities under different pressures (3–10⁵ Pa, air) and different atmospheres (N₂, Ar, and CO₂, 10⁵ Pa) are investigated. The thermal conductivities are in the range of 0.0335–0.0652 W m K^?1 under ambient pressure and 0.0098–0.0571 W m K^?1 at 3 Pa. The thermal transfer mechanism under different gas pressures is analyzed with increasing pressure. Under different atmospheres, the thermal conductivities decrease as the molecular weight of the gas increases. Compared with the traditional organic foam insulating materials of phenolic foam, polyurethane and polystyrene, which have similar apparent densities, PBO aerogels exhibit lower thermal conductivity of 0.0335 W m K^?1 than that of traditional organic foam at room temperature.     

Synthesis of polythiophene/graphene oxide composites by interfacial polymerization and evaluation of their electrical and electrochemical properties

We report a new method for the synthesis of polythiophene (PTh)/graphene oxide (GO) nanocomposites by interfacial polymerization. Polymerization occurred at the interface of two immiscible solvents, i.e. n‐hexane containing thiophene and nitromethane containing GO and an initiator. Characterizations were done using Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, and electrochemical and electrical conductivity measurements. Spectroscopic analyses showed successful incorporation of GO in the PTh matrix. Morphological analysis revealed good dispersion of GO sheets in the polymer matrix. The PTh/GO composites showed marked improvements in thermal stability and electrical conductivity (2.7 × 10^?4 S cm^?1) compared to pure PTh. The composites exhibited excellent electrochemical reversibility compared to pure PTh at a scan rate of 0.1 V s^?1. The composites were stable even up to 100 electrochemical cycles, indicating good cycle performance. The specific capacitance of the composites was calculated using cyclic voltammetry and was found to be 99 F g^?1. © 2014 Society of Chemical Industry