Measurement and Prediction of the Thermal Conductivity of Tricyanomethanide- and Tetracyanoborate-Based Imidazolium Ionic Liquids

The thermal conductivity of ten ionic liquids (ILs) based on the anions \([\mathrm{C(CN)}_{3}]^{-}\) (tricyanomethanide) and \([\mathrm{B(CN)}_{4}]^{-}\) (tetracyanoborate) carrying a homologous series of the [alkyl-MIM] \(^{+}\) (1-alkyl-3-methylimidazolium) cations [EMIM] \(^{+}\) (ethyl), [BMIM] \(^{+}\) (butyl) [HMIM] \(^{+}\) (hexyl), [OMIM] \(^{+}\) (octyl), [DMIM] \(^{+}\) (decyl) was measured by a steady-state guarded parallel-plate instrument in the temperature range between (283.15 and 353.15) K at atmospheric pressure with a total uncertainty of 5 % ( \(k\,=\,2\) ). Furthermore, the refractive index required for data evaluation and the density, which is an important property in the developed prediction method for the thermal conductivity, were determined. In general, the measured thermal conductivities of the probed ILs decrease with increasing temperature and increasing alkyl-chain length of the cation. Regarding the influence of the anion, somewhat smaller values for the \([\mathrm{B(CN)}_{4}]^{-}\) -based ILs compared to the \([\mathrm{C(CN)}_{3}]^{-}\) -based ILs carrying the same cation are observed. Our previously developed simple prediction method for the thermal conductivity of ILs at 293.15 K using only information on the molar mass and the density could be improved. By the combination of this approach with the temperature dependence of the density, an extended empirical correlation additionally describing the temperature dependence of the thermal conductivity of ILs is recommended. This correlation represents all experimental thermal-conductivity data in the literature with a standard deviation of less than 7 %.     

Thermal Conductivities of [bmim][PF<Subscript>6</Subscript>], [hmim][PF<Subscript>6</Subscript>], and [omim][PF<Subscript>6</Subscript>] from 294 to 335 K at Pressures up to 20 MPa

Thermal conductivities are reported for a series of 1-alkyl-3-methylimidazolium hexafluorophosphates having butyl, hexyl, and octyl groups, which are expressed by [bmim][PF₆], [hmim][PF₆], and [omim][PF₆], respectively. The experimental method used was a transient short-hot-wire method. Since only a small amount of sample liquid is required, this method was found to be effective for the thermal-conductivity measurements of ionic liquids (ILs). The experimental temperatures ranged from 294 to 335 K at pressures up to 20 MPa. The values of the thermal conductivities of ILs at normal pressure are similar to those of benzene. It was found that an effect of the length of the alkyl chain on the thermal conductivities in ILs is negligible. From the data for the thermal conductivity and viscosity at 293.15 K and 0.1 MPa of ILs and normal alkanes, a simple correlation was developed based on the Mohanty theory. From comparisons between the thermal conductivities of ILs and those of organic liquids (n-hexane, benzene, and methanol), the temperature and pressure dependences of the thermal conductivity of ILs are relatively weak.     

Simulation and Experimental Study on Thermal Conductivity of [EMIM][DEP] + $$\mathbf{H}_\mathbf{2}{} \mathbf{O}$$ + SWCNTs Nanofluids as a New Working Pairs

In this paper, the single-wall carbon nanotubes (SWCNTs) were dispersed into ionic liquid, 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), and its aqueous solution [EMIM][DEP](1) + \(\hbox {H}_{2}\hbox {O}(2)\) to enhance the thermal conductivity of base liquids, which will be the promising working pairs for absorption heat pumps and refrigerators. The enhancement effects on thermal conductivity were studied by experiment and molecular dynamic simulation (MD) methods. The thermal conductivities of [EMIM][DEP] + SWCNTs (INF) and [EMIM][DEP](1) + \(\hbox {H}_{2}\hbox {O}(2)\) + SWCNT(SNF) both with SWCNT mass fraction of 0.5, 1, and 2 (wt%) were measured by transient hot-wire method. The results indicate that the enhancement ratio of thermal conductivity of INF, and SNF can approach 1.30 when SWCNT is 2 (wt%). Moreover, SWCNTs has a higher enhancement ratio than multi-wall carbon nanotubes (MWCNTs). Density and thermal conductivity of [EMIM][DEP], [EMIM][DEP](1) + \(\hbox {H}_{2}\hbox {O}(2)\), INF and SNF systems, together with self-diffusion coefficients of \(\hbox {[EMIM]}^{+}\), \(\hbox {[DEP]}^{-}\), [EMIM][DEP] and water in solution [EMIM][DEP](1) + \(\hbox {H}_{2}\hbox {O}(2)\), were investigated by MD simulations. The results indicate that the maximum relative error between the simulated and experimental densities is about 2 %, and the simulated self-diffusion coefficient of [EMIM][DEP] is in the order of magnitude of \(10^{-11}\,\hbox {m}^{2}\cdot \hbox {s}^{-1}\). The average relative deviation for the simulated thermal conductivity of [EMIM][DEP](1) + \(\hbox {H}_{2}\hbox {O}(2)\), INF and SNF from experimental ones are 23.57 %, 5 %, and 5 %, respectively. In addition, the contributions of kinetic energy, potential energy, and virial and partial enthalpy terms to thermal conductivity were also calculated. The results indicate that virial term’s contribution to thermal conductivity is the maximum, which accounts for 75 % to 80 % of total thermal conductivity.     

Electrolytic Conductivity of Four Imidazolium-Based Ionic Liquids

In this article, electrolytic (ionic) conductivity measurements of four ionic liquids (ILs), namely, 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide ([C $_{2}$ 2 mim][NTf $_{2}$ 2 ]), 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([C $_{2}$ 2 mim][OTf]), 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C $_{6}$ 6 mim][NTf $_{2}$ 2 ]), and 1-ethyl-3-methylimidazolium ethyl sulfate ([C $_{2}$ 2 mim][EtSO $_{4}$ 4 ]) (ECOENG212 $^\circledR $ ® ), were performed in a temperature range of (288.15 to 333.15) K. [C $_{6}$ 6 mim][NTf $_{2}$ 2 ] was chosen to be a reference ionic liquid for several properties, including the electrolytic conductivity by the IUPAC Project 2002-005-1-100. For that reason, the measurements performed with that ionic liquid primarily serve the purpose to validate the instrumentation and the experimental procedure used in this work. The measurements were carried out using a complex impedance method, applying a novel electronic device designed and constructed for this purpose. The complete setup includes a Schott Instruments LF 913 T, used as a four-electrode conductivity cell, and a lock-in amplifier. The cell was calibrated using standard reference KCl aqueous solutions. The measurements of the impedance of the conductivity cell were carried out along a range of frequencies from (0.2 to 30) kHz, and the results were extrapolated to infinite frequency, in order to determine the electrolytic conductivity of the liquid samples. The results obtained for the ionic liquid [C $_{6}$ 6 mim][NTf $_{2}$ 2 ] were compared to reference data, and it was estimated that the overall uncertainty of the present results is better than 2 %. All the data obtained were compared with available literature data, and were analyzed and discussed in respect to the effect of temperature, cation alkyl chain length, and anion.     

Volumetric and Isentropic Compressibility Behavior of Ionic Liquid, 1-Propyl-3-Methylimidazolium Bromide in Acetonitrile,Dimethylformamide, and Dimethylsulfoxide at <Emphasis Type="Italic">T</Emphasis> = (288.15 to 308.15) K

Density and speed-of-sound data for 1-propyl-3-methylimidazolium bromide ([C₃mim][Br]) + acetonitrile (MeCN), [C₃mim][Br] + dimethylformamide (DMF), and [C₃mim][Br] + dimethylsulfoxide (DMSO) binary mixtures in the dilute concentration region are reported at T = (288.15 to 308.15) K. From these data, apparent molar volume, isentropic compressibility, excess molar volume, and isentropic compressibility deviation values have been calculated. Negative deviations from the ideal behavior of both molar volume and isentropic compressibility have been observed for all systems investigated in this study. It has been found that deviations from ideal behavior for the [C₃mim][Br] + MeCN system are larger than those for the [C₃mim][Br] + DMF system which, in turn, are larger than those for the [C₃mim][Br] + DMSO system. The results have been interpreted in terms of ion–dipole interactions and structural factors of the ionic liquid and investigated organic solvents.     

Sol–gel synthesis of vanadium pentoxide nanoparticles in air- and water-stable ionic liquids

Vanadium pentoxide (V₂O₅) nanoparticles were synthesized at moderate reaction temperatures by hydrolysis of VO[OCH(CH₃)₂]₃ in two different air- and water-stable ionic liquids with the same anion: 1-butyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py_1,4]Tf₂N) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIM]Tf₂N) via the sol–gel method using acetone and isopropanol either as refluxing solvents or as co-solvents. The cation type of the ionic liquid affects the crystallinity, morphology, and surface area of the produced nanoparticles: [Py_1,4]Tf₂N gave products with higher crystallinity especially with acetone as a refluxing and co-solvent, while [EMIM]Tf₂N gave a clear mesoporous morphology with isopropanol as a refluxing solvent. Ionic liquids affect the key factors (morphology and surface area) that make V₂O₅ an attractive material as catalyst and/or cathodic material for lithium ion batteries.     

Iridium-based light-emitting electrochemical cells containing ionic liquids in the luminous layer

To fabricate transition metal complex-based LECs (light-emitting electrochemical cells), ([Ir(ppy)₂(5,6-dime-1,10-phenthroline)]PF₆ was synthesized and used as a luminous material and ILs (ionic liquids) were incorporated into a luminous layer, in which two types of ionic liquid were used; 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄). ILs were added to a [Ir(ppy)₂(5,6-dime-1,10-phenthroline)]PF₆ luminous layer to improve ionic conductivity and light intensity. Both ILs significantly increased the current density and luminance. Due to the small molecule of BF₄^?, turn-on time was reduced and ionic conductivity was increased. However, the device stability was sacrificed. High current efficiency of 34.5 cd/A was investigated at 7 V of BMIMPF₆-doped luminous layer. The LECs based on [Ir(ppy)₂(5,6-dime-1,10-phenthroline)]PF₆ gave yellow emission color when ILs were added into light-emitting layer, and no significant change of color has been found in this study.     

Volumetric Properties of the Ionic Liquid, 1-Butyl-3-methylimidazolium Tetrafluoroborate,in Organic Solvents at <Emphasis Type="Italic">T</Emphasis> = 298.15K

Apparent molar volumes, , and compressibilities, , of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF₄]) have been determined from precise density and speed-of-sound measurements in organic solvents, methanol (MeOH), acetonitrile (MeCN), tetrahydrofuran (THF), N,N-dimethylacetamide (DMA), and dimethylsulfoxide (DMSO) in the dilute region of the ionic liquid. Corresponding values at infinite dilution are estimated by the Redlich–Mayer and Pitzer equations. The results have been interpreted by the interaction of the [BMIm][BF₄] in the organic solvents. Results show that the structure and dielectric constant of the organic solvents play an important role for the ion–solvent interactions in these mixtures. It was found that the strength of interaction between [BMIm][BF₄] with the studied organic solvents has the order DMSO > DMA > MeOH > MeCN > THF.     

Physical Properties of Pyridinium Fluorohydrogenate, [pyridine · H+][H2F3]−

Ionic liquids (ILs), also referred to as molten salts, have found application as electrolytes for batteries and super-capacitors, in electroplating baths, as designer solvents, and as reaction media. A few of the desired properties of a super-capacitor electrolyte are nonflammability, thermal stability, and electrochemical stability. ILs containing aromatic cations have been shown to have low viscosity which results in a high electrochemical conductivity. There is a delicate balance between increasing the thermal stability, or decreasing the melting point, and increasing the electrochemical conductivity of the IL. This study focuses on pyridinium fluorohydrogenate, [pyridine · H⁺][H₂F₃]⁻. Pyridinium fluorohydrogenate has been synthesized by the reaction of pyridine and anhydrous hydrofluoric acid. This IL has a relatively high electrical conductivity (~98 mS · cm⁻¹ at 23 °C), a wide electrochemical window, and a boiling point of 186 °C. A stable gel can also be formed by combining [pyridine · H⁺][H₂F₃]⁻ and a super absorbent polymer such as polyacrylic acid. The gel adds mechanical stability to the matrix while not greatly affecting the conductivity of the IL.     

Viscosity of Imidazolium-Based Ionic Liquids at Elevated Pressures: Cation and Anion Effects

The viscosity of imidazolium-based ionic liquids with four different cations and three different anions was measured to pressures of 126 MPa and at three temperatures (298.15 K, 323.15 K, and 343.15 K). The high-pressure viscosity of 1-ethyl-3-methylimidazolium ([EMIm]), 1-n-hexyl-3-methylimidazolium ([HMIm]), and 1-n-decyl-3-methylimidazolium ([DMIm]) cations with a common anion, bis(trifluoromethylsulfonyl)imide ([Tf₂N]), was measured to determine the alkyl-chain length effect of the cation. An increase in the alkyl-chain length increased the viscosity at elevated pressures. [DMIm] exhibited a larger nonlinear increase with pressure over the shorter alkyl substituents. Anion effects were investigated with [HMIm] as a common cation and anions of [Tf₂N], hexafluorophosphate ([PF₆]), and tetrafluoroborate ([BF₄]). [HMIm][PF₆], with the highest viscosity, demonstrated a very nonlinear pressure dependence even at relatively moderate pressures (to 30 MPa), similar to the results for [BMIm][PF₆]. A combined Litovitz and Tait equation was utilized to describe the viscosity of the ionic liquids with pressure and temperature and demonstrated good correlation with the experimental data.     

Electrochemical behaviors of iron-based layered double hydroxide thin-films

The ordered ultrathin films based on the fabrication of Mg/Fe-LDHs ([Mg₆Fe₂(OH)₁₆CO₃·(H₂O)_4.5]_0.375) nanosheets and hexacyanoferrate(III) anions via the self-assembly procedure were prepared. The electrodes modified by the films demonstrated a couple of well-defined reversible redox peaks attributed to [Fe(CN)₆]^3?/4? and Fe^2+/3+ couples. The effects of cycle number, scan rate and Mg/Fe molar ratio on the CV performance of the thin-film electrodes were observed in K₃[Fe(CN)₆] electrolyte. The [Fe(CN)₆]^3? pillared Mg/Fe-LDHs with Mg/Fe molar ratio of 3 (LDH-(CN)-3) demonstrated an excellent electrochemical behavior with a potential window between ??0.2 and 1.0 V, high specific capacitance and sensitivity, indicating that the high crystallinity, large specific surface area and plentiful [Fe(CN)₆]^3? anions in interlayer spaces were necessary. Especially, the interlayer [Fe(CN)₆]^3? anions significantly affected the electrochemical behavior of the electrode, where the electrode reaction was controlled by the diffusion of [Fe(CN)₆]^3?/4? and Fe^2+/3+ couples. Under current density of 2.5 A g^?1, the optimized LDH-(CN)-3 electrode exhibited high specific capacitance of 250.81 F g^?1 with good cycling stability. This facile synthesis strategy and the good electrochemical properties indicated that the LDH-(CN)-3 was a potential economical alternative material for supercapacitor application.     

Direct-on-barrier copper electroplating on ruthenium from the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide

The "direct-on-barrier" electroplating of copper on ruthenium from a 1 mol dm⁻³ solution of CuCl in the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide, [C₂mim][N(CN)₂], is reported. Continuous layers of copper with a preferential Cu(111) orientation were obtained from this electrolyte. The copper coatings were investigated by top view scanning electron microscopy (SEM), X-ray diffraction (XRD), and focused ion beam transmission electron microscopy (FIB-TEM). The nucleation density was both theoretically and experimentally evaluated by the Scharifker-Hills model and transmission electron microscopy, respectively. The direct plating of copper on resistive substrates for advanced interconnects and package is a promising new application of ionic liquids.     

Mn3O4 Nanoparticle Synthesis via Ionic Liquid-Assisted Route

Via the green chemistry route, a new class of Mn₃O₄ nanoparticles has been synthesized using 1-n-butyl-3-methylimidazolium trifluoromethane sulfonate [BMIM][TfO] ionic liquid, which serves as a capping agent. The thermal behavior, phase structure, morphology, and magnetic properties of the samples are characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM), and Vibrating sample magnetometer (VSM) studies. The phase-pure Mn₃O₄ nanocrystals with 40-nm narrow particle size distribution are obtained with the significant influence of ionic liquid. The synthesized Mn₃O₄ nanoparticles show the superparamagnetic behavior.     

1-己基-3-甲基咪唑六氟磷酸盐离子液体的微波辅助合成与结构表征

采用1-溴代己烷和N-甲基咪唑为原料,微波辅助快速合成了溴化1-己基-3-甲基咪唑([HMIM]Br)中间体,此步反应产率可达到95%。通过将中间体和六氟磷酸钾进行离子交换,制备了离子液体1-己基-3-甲基咪唑六氟磷酸盐([HMIM]PF6),产率约为48%。与传统方法相比,反应时间极大地缩短。产物的结构经傅立叶变换红外光谱(FT-IR)、超导脉冲傅立叶变换核磁共振氢谱(1HNMR)和超导脉冲傅立叶变换核磁共振碳谱(13CNMR)确认,纯度经高效液相色谱法(HPLC)分析达到99.0%以上。     

Choline- versus imidazole-based ionic liquids as functional ingredients in topical delivery systems: cytotoxicity,solubility, and skin permeation studies

Background: Poor drug solubility represents a problem for the development of topical formulations. Since ionic liquids (ILs) can be placed in either lipophilic or hydrophilic solutions, they may be advantageous vehicles in such delivery systems. Nonetheless, it is vital to determine their usefulness when used at concentrations were cell viability is maintained, which was considered herein.

Method: Five different ILs were prepared—three imidazole-based ILs: [C2mim][Br], [C4mim][Br], and [C6mim][Br]; and two choline-based ILs: [Cho][Phe] and [Cho][Glu]. Their cytotoxicity in human keratinocytes (HaCat cells), their influence in drug solubility and in percutaneous permeation, using pig skin membranes, was evaluated.

Results: Caffeine and salicylic acid were used as model actives. Choline-based ILs proved to be more suitable as functional ingredients, since they showed higher impact on drug solubility and a lower cytotoxicity. The major solubility enhancement was observed for caffeine and further solubility studies were carried out with this active in several concentrations of the choline-based ILs (0.1; 0.2; 0.5; 1.0; 3.0 and 5.0%, w/w) at 25?°C and 32?°C. Solubility was greatly influenced by concentrations up to 0.5%. The choline-based ILs showed no significant impact on the skin permeation, for both actives. The size of the imidazole-based ILs alkyl chain enhances the caffeine solubility and permeation, but also the ILs cytotoxicity. Stable O/W emulsions and gels were prepared containing the less toxic choline-based ILs and caffeine.

Conclusions: Our results indicate that the choline-based ILs were effective functional ingredients, since, when used at nontoxic concentrations, they allowed a higher drug loading, while maintaining the stability of the formulations.     

Preparation and characterization of ionic liquid intercalation compounds into layered zirconium phosphates

In this work, immobilizing a series of ionic liquids (ILs) 1-alkyl-3-methylimidazolium chloride [C _n mim]Cl (n = 2, 4, 6, 8) on the layered zirconium phosphates were investigated. [C₄mim]Cl was used to explore in detail the factors affecting intercalation. By comparing several starting materials including α-zirconium phosphate (α-ZrP), γ-zirconium phosphate (γ-ZrP) and the corresponding alkylamine preintercalated composites, it was found that the α-ZrP · 2BA (i.e., preintercalated BA were arranged in a bilayer mode at the galleries of α-ZrP) was a suitable host for intercalating ILs. Intercalation was verified with X-ray diffraction (XRD), Raman, UV–Vis and other instrumental approaches. pH effect on immobilization was investigated. Other ionic liquids including [C _n mim]Cl (n = 2, 6, 8) intercalation compounds were prepared. Based on XRD data, the interlayer distances of the studied intercalation compounds were similar, suggesting that the ionic liquids were arranged in an approximately planar manner, as confirmed by molecular modeling.     

Anion Exchange of Li+@C60 Salt for Improved Solubility

Anion exchange of [Li⁺@C₆₀]PF₆ ^? salt was performed to obtain three highly soluble Li⁺@C₆₀ salts, namely, the trifluoromethanesulfonate (OTf^?), bis(trifluoromethylsulfonyl)imide (NTf₂ ^?), and tetrakis{3,5-bis(trifluoromethyl)phenyl}borate (TFPB^?). We investigated the solubility of [Li⁺@C₆₀]OTf^?, [Li⁺@C₆₀]NTf₂ ^?, and [Li⁺@C₆₀]TFPB^? and found that, compared with [Li⁺@C₆₀]PF₆ ^?, the NTf₂ and TFPB salts had substantially higher solubility. X-ray crystal structure analysis of the TFPB salt revealed that the Li⁺@C₆₀ units spaced further apart because of the large anions in the crystal packing. We attribute the improved solubility of the salts to primarily the increased inter-fullerene distance of the Li⁺@C₆₀ cations.     

Particulate composites based on ionic liquid-treated oil palm fiber and thermoplastic starch adhesive

Pretreatment of lignocellulosic materials is a highly essential and critical task for the manufacturing of engineered composite panels. Recently, ionic liquids (ILs) have emerged as a promising green solvent for lignocellulosic biomass disintegration. In this work, the impact of IL pretreatment on the flexural and thermal properties of the thermo-molded biocomposite panels made from oil palm biomass residue and thermoplastic starch biopolymer as binder was studied. Oil palm fiber was pretreated with IL [emim][dep] (1-ethyl-3-methylimidazolium diethyl phosphate) and IL [bmim][Cl] (1-butyl-3-methylimidazolium chloride) prior to mixing with plasticized starch. The compounded mixture was then hot-pressed into composite panels. To understand the effect of IL pretreatment, lignocellulosic characterization, morphology, and thermogravimetric analysis of the untreated and treated fibers were performed. It was found that thermal stability of the oil palm biomass and the biocomposites was improved after IL pretreatment due to partial removal of hemicellulose and lignin from raw fiber. Moreover, pretreated biocomposites exhibited superior strength and modulus as compared to that of untreated sample as evidenced from flexural testing. The study plainly demonstrates that IL-assisted pretreatment could be an extremely attractive and clean technology for the efficient use of agro-based industrial waste in biocomposite field.     

Fe2O3 core-NaCo[Fe(CN)6] shell nanoparticles—Synthesis and characterization

A facile precipitation route was developed for the synthesis of cobalt hexacyanoferrate (CoHCF) as a thin shell around cores of nanoparticles of iron(III) oxide, forming nanoparticles of iron(III) oxide@CoHCF (n-Fe₂O₃@NaCo[Fe(CN)₆]). The morphology and structure of the as-prepared n-Fe₂O₃@NaCo[Fe(CN)₆] were characterized by the techniques of electron microscopies, X-ray diffraction measurements, X-ray photoelectron spectroscopy, infrared spectroscopy and thermogravimetry. Carbon composite electrodes of n-Fe₂O₃@NaCo[Fe(CN)₆] were prepared and the electrochemical behavior of the nanoparticles was evaluated using cyclic voltammetry. The redox couples of n-Fe₂O₃@NaCo[Fe(CN)₆] were investigated and the diffusion coefficients of counter cation in the shell of CoHCF were obtained. The effect of size of particles and the structure of CoHCF was also evaluated. n-Fe₂O₃@NaCo[Fe(CN)₆] represented prominent electrocatalytic activity toward the oxidation of some biologically active compounds.     

Thermal conductivity of gaseous HFC-134a,HFC-143a,HCFC-141b,and HCFC-142b

The thermal conductivity of new environmentally acceptable fluorocarbons HFC-134a (CH₂FCF₃), HFC-143a (CH₃CF₃), HCFC-141b (CH₃CCl₂F), and HCFC-142b (CH₃CCl₂F) in the gaseous phase has been measured in the temperature range 293–353 K at pressures up to 4 MPa. The thermal conductivity has been measured with a coaxial-cylinder cell on a relative basis. The apparatus was calibrated with He, Ne, Ar, Kr, N₂, CH₄, and SF₆ as reference fluids. The uncertainty of the experimental data obtained is estimated to be within 2% except for the uncertainty associated with the reference thermal-conductivity values. The excess thermal conductivity has been correlated satisfactorily as a function of density.