Rheological and thermal properties of poly(ethylene oxide)/multiwall carbon nanotube composites

Poly(ethylene oxide) (PEO) based nanocomposites were prepared by the dispersion of multiwall carbon nanotubes (MWCNTs) in aqueous solution. MWCNTs were added up to 4 wt % of the PEO matrix. The dynamic viscoelastic behavior of the PEO/MWCNT nanocomposites was assessed with a strain‐controlled parallel‐plate rheometer. Prominent increases in the shear viscosity and storage modulus of the nanocomposites were found with increasing MWCNT content. Dynamic and isothermal differential scanning calorimetry studies indicated a significant decrease in the crystallization temperature as a result of the incorporation of MWCNTs; these composites can find applications as crystallizable switching components for shape‐memory polymer systems with adjustable switching temperatures. The solid‐state, direct‐current conductivity was also enhanced by the incorporation of MWCNTs. The dispersion level of the MWCNTs was investigated with scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Microphase separated structures in the solid and molten states of double-crystal graft copolymers of polyethylene and poly(ethylene oxide)

Transitions from one microphase separated structure in the solid state to a different one in the molten state in polyethylene-graft-poly(ethylene oxide) copolymers, PE-g-PEO, were investigated by variable temperature X-ray scattering measurements and thermal analyses. Small-angle X-ray scattering patterns from polymers with PEO grafts with 25, 50 and 100 ethylene oxide (EO) units show that the polymer passes through three distinct structures at ～10 nm length scales with increase in temperature (T): lamellar structures of PE and PEO at T < T_m^PEO, PE lamellae surrounded by molten PEO at T_m^PEO < T < T_m^PE, and microphase separated structures at T > T_m^PE when both PE and PEO are molten (T_m refers to the melting temperature). These phase transformations also occur during cooling but with hysteresis. Crystalline phases of PEO side chains and PE main chains could be identified in the wide-angle X-ray diffraction profiles indicating that the PE backbone and PEO grafts crystallize into separate domains, especially with longer grafted chains (50 and 100 units). At EO segment lengths > 50, PEO shows the expected increase in melting and crystallization temperatures with the increase in the grafted chain length. PE does not affect T_m^PEO but does decrease the onset of crystallization upon cooling. PEO grafts result in fractionation of PE, decrease the melting point of PE and increase the undercooling for the onset of crystallization of PE.     

Nanodroplet formation and exclusive homogenously nucleated crystallization in confined electrospun immiscible polymer blend fibers of polystyrene and poly(ethylene oxide)

By utilizing electrospun blend fibers of polystyrene (PS) and poly(ethylene oxide) (PEO) with diameters in sub-microns, nanodroplets of the minor component (PEO) were obtained by annealing the blend fibers above the glass transition temperature (T_g) of the matrix polymer (PS), as a result of the Rayleigh-Plateau instability in the melt. However, direct thermal annealing of the PS/PEO blend fibers led to poor Rayleigh breakup of the PEO fibers in the PS matrix, and fractionated crystallization with both homogeneous and heterogeneous nucleation was observed, probably due to a broad size distribution of PEO particles. On the contrary, after confining the PS/PEO blend fibers with a high T_g polymer, poly(4-tert-butyl styrene) (P4tBS, T_g ∼ 143 °C), well-defined Rayleigh breakup of the PEO fiber was achieved by annealing the P4tBS-coated PS/PEO blend fibers at 150 °C. Consequently, exclusive homogeneously nucleated PEO crystallization was observed at −20 °C. This report could provide a universal method to achieve nano-sized droplets for the study of nanoconfinement effect by utilizing electrospun immiscible polymer blend fibers without addition of any compabitilizers.     

Influences of poly(ether urethane) introduction on poly(ethylene oxide) based polymer electrolyte for solvent-free dye-sensitized solar cells

A poly(ether urethane) (PEUR)/poly(ethylene oxide) (PEO)/SiO₂ based nanocomposite polymer is prepared and employed in the construction of high efficiency all-solid-state dye-sensitized nanocrystalline solar cells. The introduction of low-molecular weight PEUR prepolymer into PEO electrolyte has greatly enhance the electrolyte performance by both improving the interfacial contact properties of electrode/electrolyte and decreasing the PEO crystallization, which were confirmed by XRD and SEM characteristics. The effects of polymer composition, nano SiO₂ content on the ionic conductivity and I₃⁻ ions diffusion of polymer-blend electrolyte are investigated. The optimized composition yields an energy conversion efficiency of 3.71% under irradiation by white light (100 mW cm⁻²).     

Thermoviscosifying polymers based on polyether prepared from inverse emulsion polymerization

Thermoviscosifying polymers are attractive for enhancing oil recovery owing to their exceptional thickening power as temperature increases. However, the polymers reported to date show inadequacies including obligatory high polymer concentration to get the thermothickening ability because of their low molecular weight (MW), and inconvenient post‐treatment due to the high viscosity after manufacturing. To overcome these drawbacks, inverse emulsion polymerization was used here for preparing polyether‐based thermoviscosifying polymers (TVP‐Ps) by grafting acrylic monomers onto triblock copolymers PEO–PPO–PEO. It was found the MW of final products could reach 8 million Daltons, making them thermoviscosifying at 0.2 wt %. The viscosity of polymerized inverse emulsions was as low as 175 mPa·s, leading to direct dispersing. The TVP‐Ps containing Pluronic F127, F108, F68 all exhibited significant thermothickening behaviors in both aqueous solutions and brines, and the critical thermoassociative temperature could be tuned by changing the nature or amount of Pluronics. After aging at 45 °C for 60 days with equal initial viscosity, TVP‐Ps shows 21% higher viscosity retention than the reference polymer without Pluronic, PAMA, and preliminary core flooding test demonstrated TVP‐Ps can get 2.1% higher incremental oil recovery than PAMA. This work paves a new avenue for scaled‐up preparation and potential use of TVP‐Ps. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 134, 46696     

Phase behavior of LiClO4-doped poly(ε-caprolactone)-b-poly(ethylene oxide) hybrids in the presence of competitive interactions

The phase behavior of a series of LiClO₄-doped poly(ε-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) was studied as a function of PEO volume fraction (f_PEO), doping ratio (r) and temperature (T). It is found that the morphology of the hybrids changes from disordered structure (DIS) to hexagonally packed cylindrical (HEX) structure and then to lamellar (LAM) structure as the volume fraction of the PEO/salt phase (f_PEO/salt) increases at f_PEO/salt < 0.5. Order–order transitions are observed upon heating some hybrids. An approximate phase diagram of the PCL-b-PEO/LiClO₄ hybrids with f_PEO/salt < 0.5 was constructed in terms of f_PEO/salt and the segregation strength (χ_effN). As compared with the phase diagram of the weakly segregated diblock copolymers, the phase diagram of the hybrids has two features: the boundaries of the LAM and HEX structures shifts to lower f_PEO/salt and body-centered cubic spherical (BCC) structure is not observed for the samples studied. This can be attributed to the weaker ability of the salt inducing microphase separation at low f_PEO and the conformational change of the PEO block induced by the salt. Some unexpected phase behaviors were observed for the hybrids with f_PEO/salt > 0.5, including the hexagonally perforated layers (HPL) to LAM transition upon heating the same hybrid and HEX to gyroid (GYR) transition with the increase of doping ratio at the same temperature. These unexpected phase behaviors are qualitatively interpreted based on the competitive association of the PCL block with Li⁺ ions at elevated temperatures and higher doping ratios, which leads to re-distribution of the Li⁺ ions in different phases and the inconsistency between the calculated f_PEO/salt and the real volume fraction of the PEO/salt phase.     

Nanocomposite polymer electrolytes for solid-state lithium-ion batteries with enhanced electrochemical properties

Solid-state polymer electrolytes (SPEs) have attracted significant attention owing to their improvement in high energy density and high safety performance. However, the low lithium-ion conductivity of SPEs at room temperature restricts their further application in lithium-ion batteries (LIBs). Herein, we propose a novel poly (ethylene oxide) (PEO)-based nanocomposite polymer electrolytes by blending boron-containing nanoparticles (BNs) in the PEO matrix (abbreviated as: PEO/BNs NPEs). The boron atom of BNs is sp²-hybridized and contains an empty p-orbital that can interact with the anion of lithium salt, promoting the dissociation of the lithium salts. In addition, the introduction of the BNs could reduce the crystallinity of PEO. And thus, the ionic conductivity of PEO/BNs NPEs could reach as high as 1.19 × 10⁻³ S cm⁻¹ at 60°C. Compared to the pure PEO solid polymer electrolyte (PEO SPEs), the PEO/BNs NPEs showed a wider electrochemical window (5.5 V) and larger lithium-ion migration number (0.43). In addition, the cells assembled with PEO/BNs NPEs exhibited good cycle performance with an initial discharge capacity of 142.5 mA h g⁻¹ and capacity retention of 87.7% after 200 cycles at 2 C (60°C).     

Effects of frequency,molecular weight and thermal oxidation on the dynamic mechanical response of poly (ethylene oxide)

The technique of dynamic mechanical thermal analysis (DMTA), operated in the dual cantilever mode, was used to characterize the effects of frequency, crystallinity, molecular weight (MW) and the extent of thermal oxidation on the dynamic mechanical response of poly(ethylene oxide) (PEO). The glass transition temperature (T_g) of PEO (MW = 9 × 10⁵ Dalton) was found to be ?44°C. For PEO (MW = 1 × 10⁵ Dalton) the T_g is ?39°C and this value increases by 2–9°C for every decade increase in the measuring frequency. Two minor, second-order transitions of PEO are also discernible at ?33 and 32°C. An inverse dependence of T_g on molecular weight was found in the molecular weight range studied and this is contrary to the Fox-Flory theory. It was also found that a partially crystalline sample is obtained despite very rapid quenching of PEO from the melt into liquid nitrogen. Thermal oxidation of PEO before processing leads to an increase in the amplitude of the loss tangent peak. This reflects the effect of oxidation products in restricting polymer crystallization and the subsequent increase in the amorphous fraction of the polymer. The position of the T_g peak in PEO remains reasonably fixed with progressive ageing and this was attributed to crosslinking having occurred in addition to chain scission during thermal oxidation.     

Influence of octakis-functionalized polyhedral oligomeric silsesquioxanes on the physical properties of their polymer nanocomposites

We synthesized the polyhedral oligomeric silsesquioxane (POSS) derivatives octakis[dimethyl(phenethyl)siloxy]silsesquioxane (OS-POSS), octakis[dimethyl(4-acetoxy phenethyl)siloxy]silsesquioxane (OA-POSS), and octakis[dimethyl(4-hydroxyphenethyl)siloxy] silsesquioxane (OP-POSS) through hydrosilylation with octakis(dimethylsiloxy)silsesquioxane (Q₈M₈^H). To investigate the influence of these octuply functionalized POSS derivatives in polymer nanocomposites, we blended OP-POSS, OA-POSS, and OP-POSS with the homopolymer poly(ethylene oxide) (PEO) and characterized its resulting intermolecular interactions (e.g., hydroxyl-ether and carbonyl-ethylene oxide) using FTIR spectroscopy. The thermal properties of these blend systems were investigated using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The crystallization kinetics in the miscible binary blends of the crystalline polymer and these inorganic nanoparticles were also determined through DSC and optical microscopy (OM) analyses. Herein, we emphasize the effects of the functional groups on POSS nanocomposites on the crystallization kinetics of PEO. We found that OP-POSS/PEO blend had the highest thermal stability and lowest crystallization rate because its hydrogen bonding interactions (between its hydroxyl and ether units) were stronger than those (between carbonyl and methylene groups) in OA-POSS/PEO.     

Synthesis and properties of amphiphilic poly(ethylene oxide)-grafted cardo poly(aryl ether sulfone) copolymers

A series of comb-type amphiphilic copolymers (PES-g-PEO) with a stiff poly(aryl ether sulfone) backbone and flexible PEO side chains was synthesized via a “grafting onto” technique. By controlling the monomer feed ratios, high molecular weight copolymers with a range of PEO side chain content were prepared and used to form tough and flexible membranes. The PES-g-PEO membranes displayed high thermal stability (T_d > 230 °C) and good mechanical properties. The water contact angles of the PES-g-PEO membranes ranged from 60.5° to 66.7°, 20° lower than those of poly(aryl ether sulfone) membranes (82-86°), indicating that the PEO side chains improved the hydrophilicity of the membranes. Wide-angle X-ray diffraction results indicated that the PES-g-PEO membranes possessed an amorphous structure, that is, crystallization of the PEO side chains did not occur. The Li-ion conductivity reached 2.26 × 10⁻⁴ S/cm at room temperature, much higher than that of the pure PEO-based system (10⁻⁶ S/cm), due to the presence of the amorphous PEO side chains between the PES backbones, which provided an effective Li-ion transport pathway.     

Poly(ethylene oxide) crystallization in single walled carbon nanotube based nanocomposites: Kinetics and structural consequences

The overall isothermal crystallization behavior of poly(ethylene oxide) (PEO) in single walled carbon nanotube (SWNT) based nanocomposites is studied with a focus on growth kinetics and morphological evolution of PEO using differential scanning calorimetry and in-situ small angle x-ray scattering measurements respectively. The characteristic time for crystallization of PEO increases due to the presence of lithium dodecyl sulfate (LDS) stabilized carbon nanotubes. Further, analysis of crystallization data using the Lauritzen-Hoffman regime theory of crystal growth shows the PEO chains stiffen in presence of LDS with an increased energy barrier associated with the nucleation and crystal growth, and the nanotubes further act as a barrier to chain transport or enhance the efficacy of the LDS action. The energy penalty and diffusional barrier to chain transport in the nanocomposites disrupt the crystalline PEO helical conformation. This destabilization leads to preferential growth of local nuclei resulting in formation of thinner crystal lamellae and suggests that the crystallization kinetics is strongly affected by the nucleation and crystal growth events. This study is particularly interesting considering the suppression of the PEO crystallinity in presence of small fraction of Lithium ion based surfactant and carbon nanotubes.     

Kinetics of nucleation and crystallization in poly(butylene succinate) nanocomposites

Differential fast scanning calorimetry (DFSC) was employed on poly(butylene succinate) nanocomposites containing silver nanoparticles and multi-walled carbon nanotubes (MWCNT), in order to identify the temperature range of heterogeneous nucleation caused by both nanofillers. The fast scanning rates also allow investigating self-nucleation by recrystallization experiments approaching the crystallization temperature from low temperatures. The recrystallization behavior of PBSu and its nanocomposites is distinct from all other polymers studied so far as only the previously crystallized part of the material is able to recrystallize, independently on the available large number of nuclei. Since full melting of small crystals at low temperatures is observed this highlights the importance of ordered structures remaining in the polymer melt. On cooling from the melt the neat polymer did not crystallize at rates higher than 70 K/s, while the nanocomposites needed rates of 500 K/s and 300 K/s for silver and MWCNT, respectively. Below 280 K the crystallization kinetics of the matrix was almost the same with the nanocomposite samples. The nucleation mechanism changes at 280 K from heterogeneous to homogeneous. The study further confirms that below the glass transition nucleation and crystallization appears only after approaching the enthalpy value of the extrapolated supercooled liquid by enthalpy relaxation.     

Study of γ-irradiated Polymer Electrolyte for Zn Rechargeable Nanostructured Galvanic Cells by SAXS/DSC/WAXD method

(PEO)₈ZnCl₂ polymer electrolytes and nanocomposites were prepared using PEO γ-irradiated with a dose of 529 kGy. The effect of γ-radiation from a Co-60 source were studied by small-angle X-ray scattering simultaneously recorded with differential scanning calorimetry and wide-angle X-ray diffraction at the synchrotron ELETTRA. The abovementioned treatment largely enhanced the conductivity of the polymer electrolyte. A room temperature conductivity increase by up to two orders of magnitude was achieved by Turković et al. (J Electrochem Soc 154(6):A554, 2007).     

Poly(ethylene-oxide)/clay/silica nanocomposites: Morphology and thermomechanical properties

Poly(ethylene-oxide) PEO/clay/silica nanocomposites were prepared via solution intercalation by exploiting phase separation based on the bridging of particles by polymer chains. The intercalated morphology of nanocomposites was confirmed by XRD. Vibrational modes of the ether oxygen of PEO in the hybrids are shifted due to the coordination of the ether oxygen with the sodium cations of clay and the H-bonding interactions of the ether oxygen with the surface silanols of hydrophilic fumed silica. Based on SEM, the overall density of nanoparticle aggregates in the interspherulitic region was observed to be higher compared to that inside spherulites. PEO/clay/silica hybrids show significant property improvements compared to PEO/clay hybrids and pure PEO. The system containing 10 wt.% clay and 5 wt.% silica has substantially higher modulus and much lower crystallinity compared to the 15 wt.% clay system. The physics behind the reinforcement effect and the reduction of crystallinity as a function of fumed silica loading is discussed based on the morphological characterization of the hybrids. Lastly, PEO/clay/silica hybrids display good thermal stability and are much stiffer compared to pure PEO and PEO/clay nanocomposites.     

Suppression of crystallization in a plastic crystal electrolyte (SN/LiClO4) by a polymeric additive (polyethylene oxide) for battery applications

A basic problem with many promising solid electrolyte materials for battery applications is that crystallization in these materials at room temperature makes ionic mobilities plummet, thus compromising battery function. In the present work, we consider the use of a polymer additive (polyethylene oxide, PEO) to inhibit the crystallization of a promising battery electrolyte material, the organic crystal forming molecule succinonitrile (SN) mixed with a salt (LiClO₄). While SN spherulite formation still occurs at low PEO concentrations, the SN spherulites become progressively irregular and smaller with an increasing PEO concentration until a ‘critical’ PEO concentration (20% molar fraction PEO) is reached where SN crystallization is no longer observable by optical microscopy at room temperature. Increasing the PEO concentration further to 70% (molar fraction PEO) leads to a high PEO concentration regime where PEO spherulites become readily apparent by optical microscopy. Additional diffraction and thermodynamic measurements establish the predominantly amorphous nature of our electrolyte-polymer mixtures at intermediate PEO concentrations (20-60% molar fraction PEO) and electrical conductivity measurements confirm that these complex mixtures exhibit the phenomenology of glass-forming liquids. Importantly, the intermediate PEO concentration electrolyte-polymer mixtures retain a relatively high conductivity at room temperature in comparison to the semicrystalline materials that are obtained at low and high PEO concentrations. We have thus demonstrated an effective strategy for creating highly conductive and stable conductive polymer-electrolyte materials at room temperature that are promising for battery applications.     

Influence of molar mass on the thermal properties,conductivity and intermolecular interaction of poly(ethylene oxide) solid polymer electrolytes

The sample preparation pathway of solid polymer electrolytes (SPEs ) influences their thermal properties, which in turn governs the ionic conductivity of the materials especially for systems consisting of a crystallizable constituent. Majority of poly(ethylene oxide) (PEO)‐based SPEs with molar masses of PEO well above 10⁴ g mol^?1 (where PEO is crystallizable and should reach an asymptote in thermal behaviour) display molar mass dependence of the thermal properties and ionic conductivities in non‐equilibrium conditions, as reported in the literature. In this study, PEO of different viscosity‐molar masses (M _η = 3 × 10⁵, 6 × 10⁵, 1 × 10⁶, 4 × 10⁶ g mol^?1) and LiClO₄ salt (0 to 16.7 wt%) were used. The SPEs were thermally treated under inert atmosphere above the melting temperature of PEO and then cooled down for subsequent isothermal crystallization for sufficient experimental time to develop morphology close to equilibrium conditions. The thermal properties (e.g. glass transition temperature, melting temperature, crystallinity) according to differential scanning calorimetry and the ionic conductivity obtained from impedance spectroscopy at room temperature (σ _DC ～ 10^?6 S cm^?1) demonstrate insignificant variation with respect to the molar mass of PEO at constant salt concentration. These findings are in agreement with the PEO crystalline structures using X‐ray diffraction and ion ? dipole interaction by Fourier transform infrared results. © 2017 Society of Chemical Industry     

Fractional Crystallization Kinetics of Poly(ethylene oxide) in Its Blends with Poly(butylene succinate): Molecular Weight Effects

The fractional crystallization kinetics and phase behavior of PEO with different molecular weights (MWs) in its miscible crystalline/crystalline blends with PBS are studied. Both fractional crystallization kinetics and phase segregation of PEO in PBS/PEO blends are dramatically influenced by its MW. PEO with a medium MW (20 kDa) shows a significant fractional crystallization in the blends with PBS crystallized at a high T_IC,PBS, which, however, is dramatically depressed in the blends with a very low or high MW of PEO. This indicates that the PEO component with a medium MW is more ready to segregate into the interlamellar region of PBS crystals than those with a very low or high MW. The MW‐dependent fractional crystallization kinetics and phase segregation of PEO component in the PBS/PEO blends are discussed.

     

Composite polymer electrolyte incorporating WO3 nanofillers with enhanced performance for dendrite-free solid-state lithium battery

All solid-state lithium batteries (ASS-LBs) with polymer-based solid electrolytes are a prospective contender for the next-generation batteries because of their high energy density, flexibility, and safety. Among all-polymer electrolytes, PEO-based solid polymer electrolytes received huge consideration as they can dissolve various Li salts. However, the development of an ideal PEO-based solid polymer electrolyte is hindered by its insufficient tensile strength and lower ionic conductivity due to its semi-crystalline and soft chain structure. In order to lower the crystallization and improve the performance of PEO-based solid polymer electrolyte, tungsten trioxide (WO₃) nanofillers were introduced into PEO matrix. Herein, a PEO₂₀/LiTFSI/x-WO₃ (PELI-xW) (x = 0%, 2.5%, 5%, 10%) solid composite polymer electrolyte was prepared by the tape casting method. The solid composite polymer electrolyte containing 5 wt% WO₃ nanofillers achieved the highest ionic conductivity of 7.4 × 10^-4 S cm^-1 at 60 °C. It also confirms a higher Li-ion transference number of 0.42, good electrochemical stability of 4.3V, and higher tensile strength than a PEO/LiTFSI (PELI-0W) fillers-free electrolyte. Meanwhile, the LiFePO₄│PELI-xW│Li ASS-LBs demonstrated high performance and cyclability. Based on these findings, it can be considered a feasible strategy for the construction of efficient and flexible PEO-based solid polymer electrolytes for next-generation solid-state batteries.     

Effect of additives in PEO/PAA/PMAA composite solid polymer electrolytes on the ionic conductivity and Li ion battery performance

Polyethylene oxide (PEO) based-solid polymer electrolytes were prepared with low weight polymers bearing carboxylic acid groups added onto the polymer backbone, and the variation of the conductivity and performance of the resulting Li ion battery system was examined. The composite solid polymer electrolytes (CSPEs) were composed of PEO, LiClO_4, PAA (polyacrylic acid), PMAA (polymethacrylic acid), and Al₂O₃. The addition of additives to the PEO matrix enhanced the ionic conductivities of the electrolyte. The composite electrolyte composed of PEO:LiClO₄:PAA/PMAA/Li_0.3 exhibited a low polarization resistance of 881.5 ohms in its impedance spectra, while the PEO:LiClO₄ film showed a high value of 4,592 ohms. The highest ionic conductivity of 9.87 × 10⁻⁴ S cm⁻¹ was attained for the electrolyte composed of PEO:LiClO₄:PAA/PMAA/Li_0.3 at 20 °C. The cyclic voltammogram of Li⁺ recorded for the cell consisting of the PEO:LiClO₄:PAA/PMAA/Li_0.3:Al₂O₃ composite electrolyte exhibited the same diffusion process as that obtained with an ultra-microelectrode. Based on this electrolyte, the applicability of the solid polymer electrolytes to lithium batteries was examined for an Li/SPE/LiNi_0.5Co_0.5O₂ cell.     

Influence of a cyclic butylene terephthalate oligomer on the processability and thermoelectric properties of polycarbonate/MWCNT nanocomposites

The thermoelectric properties of melt-processed nanocomposites consisting of a polycarbonate (PC) thermoplastic matrix filled with commercially available carboxyl (–COOH) functionalized multi-walled carbon nanotubes (MWCNTs) were evaluated. MWCNTs carrying carboxylic acid moieties (MWCNT-COOH) were used due the p-doping that the carboxyl groups facilitate, via electron withdrawing from the electron-rich π-conjugated system. Preliminary thermogravimetric analysis (TGA) of MWCNT-COOH revealed that the melt-mixing was limited at low temperatures due to thermal decomposition of the MWCNT functional groups. Therefore, PC was mixed with 2.5 wt% MWCNT-COOH (PC/MWCNT-COOH) at 240 °C and 270 °C. In order to reduce the polymer melt viscosity, a cyclic butylene terephthalate (CBT) oligomer was utilized as an additive, improving additionally the electrical conductivity of the nanocomposites. The melt rheological characterization of neat PC and PC/CBT blends demonstrated a significant decrease of the complex viscosity by the addition of CBT (10 wt%). Optical and transmission electron microscopy (OM, TEM) depicted an improved MWCNT dispersion in the PC/CBT polymer blend. The electrical conductivity was remarkably higher for the PC/MWCNT-COOH/CBT composites compared to the PC/MWCNT-COOH ones. Namely, the PC/MWCNT-COOH/CBT processed at 270 °C exhibited the best values with electrical conductivity; σ = 0.05 S/m, Seebeck coefficient; S = 13.55 μV/K, power factor; PF = 7.60 × 10⁻⁶μW/m K⁻², and thermoelectric figure of merit; ZT = 7.94 × 10⁻⁹. The PC/MWCNT-COOH/CBT nanocomposites could be ideal candidates for large-scale thermal energy harvesting, even though the presently obtained ZT values are still too low for commercial applications.