Phase Transition Enthalpy Research Articles

Liquid crystals for IR: Part I – synthesis and properties of perfluoroalkyl or perfluoroalkoxy terminated oligophenyls

ABSTRACT Several homologous series of laterally halogenated and perfluoroalkyl or perfluoroalkoxy terminated oligophenyl derivatives, where the length of the core varies from two to four benzene rings, have been synthesised and mesomorphic properties, phase transition temperatures and enthalpies were determined. The influence of the length of the core, type and position of substituents in the molecular core has been analysed and compared with similarly substituted analogues with conventional chain systems. The lack of aliphatic protons in molecular structure generates unique infrared properties of presented materials and their mixtures.

Functionalized carbon nanotubes as phase change materials with enhanced thermal, electrical conductivity, light-to-thermal, and electro-to-thermal performances

Light- and electro-driven hexadecyl acrylate-functionalized single/multi-wall carbon nanotubes (HDA-g-SWCNT, HDA-g-MWCNT) solid-solid phase change materials (SSPCMs) were fabricated via a green Diels-Alder reaction. Both HDA-g-SWCNT and HDA-g-MWCNT show enhanced thermal and electrical conductivities, appropriate phase change temperature, almost no supercooling degree and effective phase change enthalpy. HDA was covalently grafted onto the surface of SWCNT/MWCNT. The phase transition enthalpy (ΔHh) and phase transition temperature (Thp) in the heating process, crystallization enthalpy (ΔHc) and crystallization temperature (Tcp) in the cooling process of HDA-g-SWCNT are 52 J/g, 36.7 °C, 51 J/g, and 23.7 °C, respectively. The ΔHh, Thp, ΔHc, and Tcp of HDA-g-SWCNT are 40 J/g, 38.0 °C, 39 J/g, and 26.8 °C, respectively. The HDA-g-SWCNT/HDA-g-MWCNT can effectively convert electric or light energy into thermal energy under electric field or solar illumination. Meanwhile, the electrical conductivity of HDA-g-SWCNT and HDA-g-MWCNT films reached up to 718 and 389 S/m, respectively. The phase change property and enhanced thermal conductivity of HDA-g-SWCNT and HDA-g-MWCNT enable them to be used as a heat spreader for electronic cooling applications. Furthermore, the HDA-g-SWCNT and HDA-g-MWCNT exhibited good thermal stability, great thermal reliability, and shape stability, potentially leading to new energy systems with multi-responsive performance for electronic devices, solar energy utilization, and thermal management.

On the balance between nematic and smectic phases in 2′,3′-difluoro-4,4″-dialkyl-p-terphenyls

ABSTRACTThe full homologous series of 2ʹ,3ʹ-difluoro-4,4″-dialkyl-p-terphenyls, where alkyl chains are from methyl to nonyl length, have been synthesised and mesomorphic properties, phase transition temperatures and enthalpies were measured. The influence of the terminal chain length on thermal mesophase range, phase sequence has been analysed and discussed. The odd–even and symmetric–non-symmetric effects have also been studied and its influence on smectic to nematic balance was analysed.

3D structure fungi-derived carbon stabilized stearic acid as a composite phase change material for thermal energy storage

Stearic acid (SA)/fungi-derived carbon (FDC) composite phase change materials (PCM) were fabricated by vacuum impregnation, where three types of FDC (FDC-C, FDC-H, and FDC-K) as carrier were synthesized by diverse synthetic procedures of carbonization. The FDC-K modified by synergistic hydrothermal and KOH-assisted calcination process had a 3D-cellular structure with considerably higher inner surface area (1799.48 m2 g−1) and cumulative pore volume (0.7476 cm3 g−1) than other matrixes, leading to that a loading capability value of SA (LC, %) in SA/FDC-K composite was up to 344.64%. X-ray diffraction and Fourier transform infrared spectroscopy shown that physical interaction instead of chemical reaction happened between FDC and SA. X-ray photoelectron spectroscopy indicated that KOH-assisted calcination treatment improved oxygenic functional groups on matrix surface so that facilitating SA loading. Raman spectra illustrated the IG/ID value of three amorphous carbons were ∼1.04. For SA/FDC-K composite, it had a melting and freezing enthalpy of 144.8 J g−1 and 142.6 J g−1, respectively, and phase transition point of 52.72 °C and 52.95 °C, respectively. The thermal conductivity (0.574 W m−1 K−1) was 115% higher than pure SA. It was also stable in terms of thermal and chemical after thermal cycles in heating and cooling. Thus, the SA/FDC-K exhibited high phase transition enthalpy and excellent thermal stability has potential application in thermal energy storage.

Investigation of the effect of beef moisture content on the amount of bound moisture with the calorimetric method

With the development of food processing and storage at near-cryoscopic temperatures, more and more attention is being paid to the development of methods for frozen out moisture and cryoscopic temperature calculating based on their component composition data. There is a significant dispersion among the existing experimental data of various researchers and calculation methods for beef thermophysical properties. In the study given, the authors determined the enthalpy of phase transitions, beet heat capacity with different moisture content and its cryoscopic temperature with the method of differential scanning calorimetry. With the analysis of the phase transitions enthalpy, it was found out that the share of non-freezing water for beef is n = 0.35 (g of water per 1 g of dry matter). The presence of the vitreous phase in the temperature range of about -85 ° С was established, most noticeably manifested when the moisture content of the samples is w = 37–45.8%, which indicates the formation of amorphous solutions in the process of food products freezing. Beginning of moisture melting peak Tm.b. takes place at temperatures range from -35 ° C till -25 ° C for the samples with low and normal moisture content respectively. Acccording to the theoretical Heldman ratio, a dependence for cryoscopic temperature calculating was proposed . The given semi-empirical dependences of the phase transitions enthalpy and the frozen moisture fraction provide an increase in the accuracy of calculations at low values of moisture content in the product. The research results can be used as input data in mathematical modeling of heat exchange processes and the development of calculating methods for the thermophysical properties of food products based on their composition.

Intensification in biological properties of chitosan after γ-irradiation.

Chitosan, a functional biopolymer, was irradiated with 100 kGy gamma irradiation and used to access its physical, antioxidant, plant growth promoting and antimicrobial properties. The molecular weight of chitosan reduced to 82.2 kDa from 337.7 kDa after irradiation. UV-Vis spectroscopy and FTIR results revealed slight changes in chitosan skeleton after irradiation but the degree of acetylation of both chitosan was ~18%. DSC profile indicated a prominent decline in enthalpy and energy for phase transition, TGA indicated shift in decomposition temperature, while XRD analysis showed a reduction in chitosan crystallinity after irradiation. DPPH and ABTS radical scavenging activity of chitosan (2-10 mg/mL) enhanced significantly by 1.25-1.45 and 1.80-3.14 folds after irradiation. There was a considerable improvement in morphological parameters (number of leaves, nodes, height, fresh weight and dry weight) and biochemical parameters (chlorophyll, total soluble sugars and soluble proteins content) of in vitro potato plant in chitosan supplemented medium at 75 mg/L concentration than the control. The minimum inhibitory concentration of normal and irradiated chitosan for Alternaria spp. was 2500 and 2000 mg/L and for Fusarium spp. was 1750 and 1500 mg/L, respectively. IC50 value of normal and irradiated chitosan for Fusarium spp. was 1387.9 ± 9.2 and 954.3 ± 6.1 mg/L, and for Alternaria spp. was 1536.1 ± 24.3 and 1416.8 ± 3.5 mg/L, respectively.

Preparation and characterization of sodium sulfate pentahydrate/sodium pyrophosphate composite phase change energy storage materials

Sodium thiosulfate pentahydrate (Na2S2O3·5(H2O)) has poor cycling stability, experiences phase separation and low crystallization due to large supercooling. In order to improve these properties, the influences of nucleating agent and thickening agent on the supercooling degree, phase separation and exothermic performance of Na2S2O3·5(H2O) were investigated by using the fusion-curing cycle and step-cooling curve system. Observation of the structure and testing of its thermophysical properties by scanning electron microscope, thermostatic bath and differential scanning calorimeter were carried out. The results show that, the addition of sodium pyrophosphate (TSPP) with a mass fraction of 0.08% had a significant improvement effect, and the thickener sodium acrylate (PASS) had the best results. A phase change composite material (CPCM) with a mass fraction of 0.08% TSPP and 2% PAAS had a phase transition temperature of 47.3 °C; the degree of subcooling was 3.6 °C; the phase transition enthalpy was 206.8J/g; the discharge time was 106 min. There was no phase separation during the storage/discharge process. After 100 high and low temperature cycles, the phase transition temperature of the composite was 42.5 °C; the phase transition enthalpy was 202.1J/g, and the cycle stability was good. The improved energy storage material can be used in building heat storage system.

Thermodynamic properties of tin: Part I Experimental investigation, ab-initio modelling of α-, β-phase and a thermodynamic description for pure metal in solid and liquid state from 0 K

Thermodynamic data for crystalline white and grey tin were assessed using an extended Einstein model from 0 K. Ab-initio simulations in the framework of density functional theory (DFT) with the quasiharmonic approximation (QHA) were carried out to define the heat capacities for both phases of tin from 0 K up to room temperatures. Good agreement was observed between theoretical and experimental heat capacities, which makes it possible to combine theoretical and experimental data to determine the standard entropies. Data for the liquid phase were described using a two state model. During the assessment, careful analysis of the experimental data was carried out. In order to fulfil the need for a precise evaluation of So298 we needed to use an additional technique using multiple Einstein functions, which allows the experimental heat capacity and enthalpy data for the solid phase to be approximated accurately from 0 K up to the melting point and to estimate solid phase transition entropy and enthalpy which are difficult to measure due to a high activation barrier. Additional measurements of heat capacity were carried out where existing data were scarce.

A robust multiphase isenthalpic flash model for water/solvent/hydrocarbon systems at high pressures and elevated temperatures

Based on the assumption that only the presence of water and solvent is considered in the aqueous phase, a robust and pragmatic water-associated isenthalpic flash (WAIF) model has been developed to perform multiphase isenthalpic flash calculations for water/solvent/hydrocarbon mixtures at high pressures and elevated temperatures. More specifically, the phase boundary diagram in enthalpy-temperature (H-T) space is constructed first for a given water/solvent/hydrocarbon system at a specified pressure. Then, the phase transition enthalpies and temperatures are determined from the H-T diagram, and thus one-, two-, or three-phase isenthalpic flash calculations can be conducted directly without resorting to stability test for a given system at a specified enthalpy and pressure. In addition, a recursive method has been proposed to initialize the temperature so that the energy conservation equation and material balance equation can be solved simultaneously to overcome the convergence difficulties. The newly proposed isenthalpic flash model has been compared with the water-free isenthalpic flash (WFIF) model and conventional three-phase isenthalpic flash (CTIF) model through three case studies. The WAIF model is found to handle the narrow-boiling constraints effectively and accurately. Furthermore, as for Water/C3H8/C16H34 mixture and Water/CO2/C16H34 mixture, a good agreement is achieved between the WFIF model and the WAIF model as the solubility of solvents (i.e., C3H8 and CO2) in the aqueous phase is quite small. With respect to Water/dimethyl ether (DME)/C16H34 mixture, however, the WAIF model is found to more accurately predict the phase behaviour of water/solvent/hydrocarbon mixtures than the WFIF model since the solubility of DME in the aqueous phase cannot be neglected. The case studies demonstrate that the newly developed water-associated isenthalpic flash model for water/solvent/hydrocarbon systems is robust, efficient, and accurate.

Evidence for ATP Interaction with Phosphatidylcholine Bilayers

ATP is a fundamental intracellular molecule and is thought to diffuse freely through the cytosol. However, evidence obtained from nucleoside-sensing sarcolemmal ion channels and red blood cells suggest that ATP is compartmentalised or buffered, especially beneath the sarcolemma. Macromolecular crowding of the cytosolic compartment, tortuosity of cytoskeletal structures and non-hydrolysing binding sites on cytoskeletal proteins are some of the physical barriers proposed that could potentially reduce free diffusion of adenine nucleotides through the cytosol. In this study we compared ATP and adenosine using a spectroscopic study of RH421, a membrane bound electrochromic dye, impedance spectroscopy measurements with tethered phospholipid bilayers and differential scanning calorimetry to determine the interaction with zwitterionic phospholipid bilayers. We report a concentration dependent shift of the excitation spectrum of RH421 indicating an interaction between ATP and DOPC unilammelar vesicles, with little effect observed from adenosine. This was supported by a concentration dependent change in the calculated membrane conductance of tethered phospholipid bilayers with ATP and not adenosine. Concentration dependent alterations to the measured enthalpy of the DMPC main phase transition with ATP was also observed, which weren’t replicated with adenosine. These observations provide strong evidence for the interaction of ATP with zwitterionic phospholipid bilayers at physiologically relevant concentrations. An interaction between ATP and the phospholipid bilayer could create a population of ATP molecules with a divergent diffusion rate with respect to “free” ATP and thus establish spatially distinct areas of compartmentalised ATP beneath the sarcolemma.

N-phenyl-carbazole as a potential liquid organic hydrogen carrier: Thermochemical and computational study

The liquid organic hydrogen carriers (LOHCs) are promising materials for hydrogen storage. The standard molar enthalpy of formation, ΔfHmo(cr, 298.15 K) = (196.0 ± 4.9) kJ·mol−1, of N-phenyl-carbazole was obtained from high-precision combustion calorimetry. The standard molar enthalpy of sublimation ΔcrgHmo(298.15 K) = (116.1 ± 1.7) kJ·mol−1 and vaporisation ΔlgHmo(298.15 K) = (100.5 ± 1.6) kJ·mol−1 of N-phenyl-carbazole were derived from the vapour pressure temperature dependences measured by the transpiration method. The standard molar enthalpy of fusion ΔcrlHmo = (19.4 ± 0.3) kJ·mol−1 at Tfus = 367.9 K was measured by DSC. Gas phase molar enthalpy of formation of N-phenyl-carbazole calculated by the high-level quantum-chemical method G4 ΔfHmo(g, 298.15 K) = (312.9 ± 3.5) kJ·mol−1, was in an excellent agreement with the experimental result (312.1 ± 5.2) kJ·mol−1. The hydrogenation/dehydrogenation reaction enthalpy result (−519.3 ± 6.6) kJ·mol−1 of N-phenyl-carbazole was calculated and compared with the data for other potential liquid organic hydrogen carriers. Phase transition enthalpies were validated with the help of empirical methods. A set of thermodynamic properties of N-phenyl-carbazole were recommended as reliable benchmark properties for thermochemical calculations. Due to the high hydrogen storage capacity, as well as the ability to form overcooled liquid even by room temperature, this compound could be considered as seminal candidate for LOHC.

Enhance the electrical conductivity and charge storage of nematic phase by doping 0D photoluminescent graphene was prepared with small organic molecule as a new array quantum dot liquid crystal displays

The E7 Nematic liquid crystal (NLC) doped with Graphene quantum dots (GQDs) have been obtanied by bottom-up approaches to improve thermodynamics and electrochemical properties. The NI phase transition temperature and enthalpy were increased in comparison with the pure E7. The anchoring effect plays a key role in NI phase transition Also, the Ea values was decreased in doped GQDs system comapre to pure E7. The electrical conductivity of the doped GQD system was significantly more than pure E7. GQDs doping does significantly affect the permittivity of the nematic host, it noticeably increases its charge capacitance.

An influence of Al2O3 nanoparticles on the caloric properties and parameters of the phase transition of isopropyl alcohol in solid phase

In present paper we investigated the influence of Al2O3 nanoparticles on the specific heat capacity of isopropyl alcohol in the temperature range 80–186 K. The measurements of the specific heat capacity were performed by an adiabatic calorimeter. It was found that below the melting temperatures the solution of isopropyl alcohol with Al2O3 nanoparticles can be in crystalline, glassy and liquid metastable states. The presence of Al2O3 nanoparticles in isopropyl alcohol leads to a decrease of the specific heat capacity and the enthalpy of phase transitions “crystalline state – liquid” and “glassy state – liquid metastable state”. It was demonstrated that not only presence of the nanoparticles but also the existence of the adsorbed interfacial phase from the molecules of the base liquid around the nanoparticles decreases the isopropyl alcohol melting heat. Based on obtained experimental data for the melting heat of the nanofluids of isopropyl alcohol/Al2O3 the mass fraction of the base fluid in the interfacial phase and the mean equivalent radius of nanoparticles with interfacial phase have been determined at the melting point.

Physicochemical and thermodynamic properties of the {1-alkyl-1-methylpiperidinium bromide [C1Cn=2,4PIP][Br], or 1-butylpyridinium bromide, [C4Py][Br], or tri(ethyl)butylammonium bromide [N2,2,2,4] [Br] + water} binary systems

This work is a continuation of our comprehensive study of ionic liquids, ILs (including organic salts with melting temperature above 100 °C) and their aqueous solutions as a novel alternative working pair for the absorption heat pump. A series of organic salts: 1-ethyl-1-methyl-piperidinium bromide, [C1C2PIP][Br], 1-butyl-1-methyl-piperidinium bromide, [C1C4PIP][Br], 1-butylpyridinium bromide, [C4Py][Br] and tri(ethyl)butylammonium bromide, [N2,2,2,4][Br] have been synthesized. The structures of compounds have been confirmed using NMR spectra. The basic thermal characterization of pure organic salts, including temperature and enthalpy of phase transition (Ttr, ΔtrH), temperature and enthalpy of melting (Tfus, ΔfusH) have been measured using a differential scanning microcalorimetry technique (DSC). The physico-chemical properties that are: density (ρ) and dynamic viscosity (η) of the tested binary systems have been determined at wide temperature and composition range. From experimental densities data, the apparent molar volumes (Vϕ,1) were calculated. In order to obtain limiting apparent molar volumes (Vϕ,10), the concentration dependence of apparent molar volumes was correlated with Redlich–Mayer type equation. Additionally, the limiting molar expansibilities (Eϕ0) and isobaric thermal expansion coefficients (αP) have been calculated. Temperature dependence of the dynamic viscosity has been correlated using VFT equation. The solid−liquid phase equilibria (SLE) have been determined using a dynamic method and correlated using NRTL equation. The influence of the alkyl chain length in the piperidinium cation substituent, as well as the cation structure, on investigated properties are presented and discussed.

Novel solid–solid phase-change cascade systems for high-temperature thermal energy storage

In this work, we investigate novel solid–solid phase-change cascade systems based on mixtures of lithium and sodium sulfates. Solid–solid phase-change materials (PCMs) can be coupled with concentrated solar power technologies. They present several advantages over solid–liquid PCMs including lower thermal expansion, lower or no corrosiveness, and no need for encapsulation. In solid–solid PCMs, the energy is stored during crystal structure transitions. Specifically, lithium sulfate undergoes a crystal structure transition (monoclinic to cubic) at 576 °C, which is a suitable temperature for concentrated solar thermal technologies. Due to the high cost of lithium sulfate, we evaluated the potential of mixing lithium with sodium sulfate to create solid–solid cascaded PCM systems to provide higher thermal storage densities. We used differential scanning calorimetry, high-temperature in situ X-ray diffraction and thermogravimetric analysis to evaluate the phase-transition temperature, phase-change enthalpy, specific heat capacity, crystalline phase composition and thermal expansion. The obtained values for heat capacity and enthalpies of phase transitions showed good agreement with available thermodynamic databases. Therefore, further calculations of thermodynamic properties of each mixture in the system were performed for designing cascaded latent thermal energy storage system. From the PCM mixtures studied, NaLiSO4 shows the greatest stability under ambient conditions. A mixture of 59.17% NaLiSO4 and 40.83% Li2SO4 allows an optimum charge of both PCMs for power cycles such as supercritical CO2. Economic assessment revealed that this cascade system has an estimated cost of $50.2 kWhth−1.

Synthesis and mesomorphic properties of 4,4”-dialkynyl-2’,3’-difluoro-p-terphenyls – the influence of C≡C acetylene linking bridge

ABSTRACTDielectrically negative liquid crystals (LC) based on the terphenyl molecular core are widely used class of rod-like mesogenes. One of the most important parameters from applications point of view is optical anisotropy at nematic phase. Hence some applications require high values of birefringence (optical anisotropy in the case of nematic medium), which can be ensured by mesomorphic molecules having high anisotropy of electronic polarisabilities Δα. The molecular design of presented terphenyls is based on the idea of elongation of conjugated π electronic system by terminal acetylene bridge (C ≡ C), as a linking element to terminal alkyl chains. In this work, we developed synthesis of 4,4’’-dialkynyl-2’,3’-difluoroterphenyls with different length of terminal alkyl chains. All synthesised compounds have wide nematic phase ranges. Synthetic problems of this work will be presented. The purity and structures of the final products and intermediates were confirmed by spectral methods: gas chromatography GC-MS, GC-FID, IR spectroscopy and nuclear magnetic resonance NMR. The phase transition temperatures, phase situation and enthalpy data were determined by polarising optical microscopy (POM) and differential scanning calorimetry.

Extracorporeal magnetic thermotherapy materials for self-controlled temperature through phase transition

Temperature regulation of magnetic thermotherapy used for the treatment of diseases needs to be precise and accurately controllable. Substantial efforts have been focused recently on manipulating the parameters of alternating magnetic field (AMF) and developing nanoparticles with low Curie temperatures for a desired thermotherapy temperature. Herein, a simple and effective approach for temperature control in magnetic thermotherapy through phase transition is reported. In general, extracorporeal magnetic thermotherapy materials are synthesized by introducing superparamagnetic nanoparticles in a phase change material with high phase transition enthalpy in the thermotherapy temperature range of 41 °C–47 °C. Given the magnetothermal effect of superparamagnetic nanoparticles and temperature control characteristics by phase transition of a phase change material, the temperature of the material in AMF can be self-regulated in the thermotherapy range. Moreover, the materials exhibit excellent thermal stability, form-stable properties, and outstanding reproducibility in temperature control for repeated use. This novel strategy may open a promising avenue for the study of temperature self-controlled thermotherapy.

Disruptive effect of tocopherol oxalate on DPPC liposome structure: DSC, SAXS, and fluorescence anisotropy studies

α-Tocopherol oxalate (TO), a tocopherol ester derivative, was investigated for its effect on the structural changes of fully hydrated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes, as a function of concentration and temperature, by applying differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), and DPH fluorescence anisotropy methods. The DSC and DPH anisotropy data indicated that TO embedded into DPPC membrane lowered the enthalpy (ΔHm) and temperature (Tm) of the main phase transition as well its cooperativity. Fluidization of the membrane at a lowered temperature was accompanied by formation of mixed structures of tocopherol-enriched domains. SAXS studies showed the formation of various ordered structures in DPPC gel-phase during incorporation of TO into the bilayer, as evidenced by the existence of lamellar phases with repeat distances (d) of 6.13 and 6.87 nm, assigned to TO-enriched domains and a lamellar, liquid-ordered DPPC phase with d = 8.45 nm at increasing TO concentrations with lowering and broadening of the Bragg peaks, and diffuse scattering, characteristic of a fluid Lα phase, were observed. In DPPC fluid-phase, the increasing presence of TO at low concentrations resulted in the appearance of a liquid-ordered phase with repeat d = 6.9 nm coexistent with a lamellar structure with d = 9.2 nm, assigned to liquid-disordered structures. An increasing repeat distance observed with raising the TO amount in the DPPC bilayer evolved from an increasing interlamellar water layer of increasing thickness. Presence of TO facilitated penetration of water molecules into the acyl chain region which decreased van der Waals interactions in the bilayer. The DSC, SAXS, and fluorescence anisotropy data established that TO exhibited pronounced disruptive activity in DPPC membranes compared to α-tocopherol. The driving force of the observed action was attributed to electrostatic and dipole interactions of the acidic moiety with the polar head group of phospholipids in the interface region of the bilayer.

Phase Transitions in Higher-Melting Ionic Liquids: Thermal Storage Materials or Liquid Crystals?

To assess the application potential of a material in thermal energy storage, the knowledge of their thermophysical properties is of key importance. Specifically, an efficient material has to show, among others, large enthalpies of phase change and a sufficiently large thermal conductivity.In this work, imidazolium-based ionic liquids (ILs) with long alkyl chain substituents 1-hexadecyl-3-methylimidazolium chloride and 1-hexadecyl-3-methylimidazolium saccharinate were studied in view of their possible use as phase-change materials. Differential scanning calorimetry (DSC) and the heat-leak modulus methods were used to determine the temperatures and the enthalpies of phase transitions in the studied ILs, enabling us to study the influence of the heating rates on the measured properties. Enthalpies of fusion near to or larger than 100 J·g–1 were found in the studied ionic liquids, making them promising candidates for thermal energy storage. Furthermore, peaks corresponding to possible liquid crystalline phases in the DSC traces of 1-hexadecyl-3-methylimidazolium saccharinate were observed.The measured properties are not only essential characteristics of a thermal storage material, temperatures and enthalpies of melting are necessary in thermodynamic description and modelling of solid-liquid phase behavior and thus in the possible utilization of the material in separation and crystallization processes.

Study of the physicochemical properties of protein kinase CK2 inhibitors -TBBt, TBBi and 2-Me-TBBi

The examination of physicochemical properties of selected protein kinase CK2 inhibitors: 4,5,6,7-tetrabromo-1H-benzotriazole (TBBt), 4,5,6,7-tetrabromo-1H-benzimidazole (TBBi) and 4,5,6,7-tetrabromo-2-methyl-1H-benzimidazole (2-Me-TBBi) was performed. The study includes modification of synthesis method and determination of compounds' thermal properties, the solid-liquid phase equilibria and pKa. Thermal properties (melting temperature, enthalpy of fusion, temperature and enthalpy of phase transitions) were determined by means of differential scanning calorimetry (DSC). For solid-liquid phase equilibria study, as a solvent, three liquids were used independently: water, ethanol and 1-octanol. In order to elicit the inhibitors’ solubility with alcohols (ethanol and 1-octanol), the dynamic method was applied. In the case of poorly soluble inhibitors in water, equilibria were determined by spectrophotometric method. Based on a phase diagram obtained results were interpreted and correlated using three equations: Wilson equation, NRTL equation and UNIQUAC equation.pKa values of studied polybrominated benzoazoles were estimated by the spectrophotometric Bates–Schwarzenbach method at two constant temperatures: 298.15 K as a room temperature and 310.15 K as a human body temperature.Obtained results are very important for further design of CK2 inhibitors, because they provide information about the solubility of pharmacophore in binary systems: active compound (1) + solvent (2), that may be used in differentiating the way how to apply potential drug. Moreover, all values of dissociation constants bring valuable guidelines to establish the therapeutic dose of pharmaceutics.