The molar heat capacities of the binary mixture composed of water and n-butanol were measured with an adiabatic calorimeter in the temperature range 78–320 K. The functions of the heat capacity with respect to thermodynamic temperature were established. A glass transition, solid–solid phase transition and solid–liquid phase transition were observed. The corresponding enthalpy and entropy of the solid–liquid phase transition were calculated, respectively. The thermodynamic functions relative to a temperature of 298.15 K were derived based on the relationships of the thermodynamic functions and the function of the measured heat capacity with respect to temperature.
The molar heat capacities
of the pure samples of acetone and methanol, and the azeotropic mixture composed
of acetone and methanol were measured with an adiabatic calorimeter in the
temperature range 78–320 K. The solid–solid and solid–liquid
phase transitions of the pure samples and the mixture were determined based
on the curve of the heat capacity with respect to temperature. The phase transitions
took place at 126.160.68 and 178.961.47 K for the sample of
acetone, 157.790.95 and 175.930.95 K for methanol, which were
corresponding to the solid–solid and the solid–liquid phase transitions
of the acetone and the methanol, respectively. And the phase transitions occurred
at 126.580.24, 157.160.42, 175.500.46 and 179.740.89
K corresponding to the solid–solid and the solid–liquid phase
transitions of the acetone and the methanol in the mixture, respectively.
The thermodynamic functions and the excess thermodynamic functions of the
mixture relative to standard temperature 298.15 K were derived based on the
relationships of the thermodynamic functions and the function of the measured
heat capacity with respect to temperature.
The heat capacities of N-(tert-butoxycarbonyl)-l-phenylalanine (abbreviated to NTBLP in this article), as an important chemical intermediates used to synthesize proteins and polypeptides, were measured by means of a fully automated adiabatic calorimeter over the temperature range from 78 to 350 K. The measured experimental heat capacities were fitted to a polynomial equation as a function of temperature. The thermodynamic functions, HT − H298.15K and ST − S298.15K, were calculated based on the heat capacity polynomial equation in the temperature range of (80–350 K) with an interval of 5 K. The thermal stability of the compound was further studied using TG and DSC analyses; a possible mechanism for thermal decomposition of the compound was suggested.
A complex of Erbium perchloric acid coordinated with l-aspartic acid and imidazole, Er2(Asp)2(Im)8(ClO4)6·10H2O was synthesized for the first time. It was characterized by IR and elements analysis. The heat capacity and thermodynamic properties of the complex were studied with an adiabatic calorimeter (AC) from 80 to 390 K and differential scanning calorimetry (DSC) from 100 to 300 K. Glass transition and phase transition were discovered at 220.45 and 246.15 K, respectively. The glass transition was interpreted as a freezing-in phenomenon of the reorientational motion of ClO4− ions and the phase transition was attributed to the orientational order/disorder process of ClO4− ions. The thermodynamic functions [HT − H298.15] and [ST − S298.15] were derived in the temperature range from 80 to 390 K with temperature interval of 5 K. Thermal decomposition behavior of the complex in nitrogen atmosphere was studied by thermogravimetric (TG) analysis and differential scanning calorimetry (DSC).
Authors:S. Yu, S. Wang, Z. Tan, C. Liao, and Y. Li
A novel AB2-type monomer diethyl 5-(4-hydroxyethoxyphenylazo)isophthalate for preparing hyperbranched azo polymers (HBPAZO) was synthesized.
The monomer obtained was characterized by IR spectra, UV–Vis spectra, 1H NMR spectrum and C NMR spectrum. The TG-DTG/DTA curves show that the decomposition of the monomer proceeds in four steps.
During the second-step decomposition, the mass loss occurs between 480.5 K and 579.0 K and the phenomena of condensing to
HBPAZO for the melted monomer was found. So it is inferred that this temperature range is the best for polycondensation of
the melted monomer, which is very important for synthesizing of HBPAZO.
Authors:X.-Z. Lan, Z.-C. Tan, Q. Shi, and Z.-H. Gao
A novel gelling method was studied to stabilize phase change material Na2HPO4 · 12H2O with amylose grafted sodium acrylate. Gelled Na2HPO4 · 12H2O shows stable heat storage performance prepared at optimized conditions: 2.7mass/mass% sodium acrylate, 0.4 mass/mass% amylose,
0.05–0.09 mass/mass% N, N′-methylenebisacrylamide, 0.05–0.09 mass/mass% K2S2O8 and Na2SO3 (mass ratio 1:1), at 50 °C. Na2HPO4 · 12H2O was dispersed in gel network as tiny crystals less than 0.1 mm. Melting points were in the range 35.4 ± 2 °C. Short-term
thermal cycling proves the effectiveness of the novel method for eliminating phase separation in the gelled salt. Adiabatic
calorimetric measurement of heat capacities shows two phase transitions, which correspond to melting of Na2HPO4 · 12H2O and freezable bond water in gel, respectively. Heat of fusion of pure Na2HPO4 · 12H2O was determined as 260.9 J g−1. Distribution of extra water is: free water:freezable water:nonfreezing water = 0:0.85:0.15.
Authors:Y.-J. Song, S.-H. Meng, F.-D. Wang, C.-X. Sun, and Z.-C. Tan
Polyimide BTDA-ODA sample was prepared by polycondensation or step-growth polymerization method. Its low temperature heat capacities were measured by an adiabatic calorimeter in the temperature range between 80 and 400 K. No thermal anomaly was found in this temperature range. A DSC experiment was conducted in the temperature region from 373 to 673 K. There was not phase change or decomposition phenomena in this temperature range. However two glass transitions were found at 420.16 and 564.38 K. Corresponding heat capacity increments were 0.068 and 0.824 J g–1 K–1, respectively. To study the decomposition characteristics of BTDA-ODA, a TG experiment was carried out and it was found that this polyimide started to decompose at ca 673 K.
Authors:X.-C. Lv, Z.-C. Tan, Z.-A. Li, Y.-S. Li, J. Xing, Q. Shi, and L.-X. Sun
The (R)-BINOL-menthyl dicarbonates,
one of the most important compounds in catalytic asymmetric synthesis, was
synthesized by a convenient method. The molar heat capacities Cp,m
of the compound were measured over the temperature range from 80 to 378 K
with a small sample automated adiabatic calorimeter. Thermodynamic functions
[HT–H298.15] and [ST–S298.15] were derived in the
above temperature range with a temperature interval of 5 K. The thermal stability
of the substance was investigated by differential scanning calorimeter (DSC)
and a thermogravimetric (TG) technique.
Authors:W.-C. Xie, X.-H. Gu, Z.-C. Tan, J. Tang, G.-Y. Wang, C.-R. Luo, and L.-X. Sun
To develop thermal stable flavor, two glycosidic bound flavor precursors, geranyl-tetraacetyl-β-D-glucopyranoside (GLY-A) and geranyl-β-D-glucopyranoside (GLY-B) were synthesized by the modified Koenigs–Knorr reaction. The thermal decomposition process and pyrolysis products of the two glycosides were extensively investigated by thermogravimetry (TG), differential scanning calorimeter (DSC) and on-line pyrolysis-gas chromatography mass spectroscopy (Py-GC-MS). TG showed the Tp of GLY-A and GLY-B were 254.6 and 275.7°C. The Tpeak of GLY-A and GLY-B measured by DSC were 254.8 and 262.1°C respectively.
Py-GC-MS was used for the simply qualitative analysis of the pyrolysis products at 300 and 400°C. The results indicated that: 1) A large amount of geraniol and few by-products were produced at 300°C, the by-products were significantly increased at 400°C; 2) The characteristic pyrolysis product was geraniol; 3) The primary decomposition reaction was the cleavage of O-glycosidic bound of the two glycosides flavor precursors. The study on the thermal behavior and pyrolysis products of the two glycosides showed that this kind of flavor precursors could be used for providing the foodstuff with specific flavor during heating process.
The heat capacities of chrysanthemic acid in the temperature range from 80 to 400 K were measured with a precise automatic
adiabatic calorimeter. The chrysanthemic acid sample was prepared with the purity of 0.9855 mole fraction. A solid-liquid
fusion phase transition was observed in the experimental temperature range. The melting point, Tm, enthalpy and entropy of fusion, ΔfusHm, ΔfusSm, were determined to be 390.7410.002 K, 14.510.13 kJ mol-1, 37.130.34 J mol-1 K-1, respectively. The thermodynamic functions of chrysanthemic acid, H(T)-H(298.15), S(T)-S(298.15) and G(T)-G(298.15) were reported with a temperature interval of 5 K. The TG analysis under the heating rate of 10 K min-1 confirmed that the thermal decomposition of the sample starts at ca. 410 K and terminates at ca. 471 K. The maximum decomposition
rate was obtained at 466 K. The purity of the sample was determined by a fractional melting method.