B.V. Lebedev

Thermodynamics of 4-methylcyclohexene, glycollide, and 1,1,3,3,5,5-hexaethylcyclotrisiloxane from 13.4 to 400 K

The temperature dependence of the isobaric heat capacities and the temperatures and enthalpies of physical transitions of 4-methylcyclohexene, glycollide, and 1,1,3,3,5,5-hexaethylcyclotrisiloxane have been studied between 13.4 and (330 to 400) K in adiabatic and vacuum-adiabatic calorimetric cryostats within about 0.2 per cent. Various physical transitions of the substances studied have been observed and characterized. From the results the functions Δ0THmo, Δ0TSmo, and Φmo have been calculated over the range 0 to (330 to 400) K for po = 1.01325 × 105 Pa. The enthalpy of combustion of glycollide has been measured in an isothermal calorimeter with an accuracy of 0.05 per cent. The standard molar thermochemical quantities of the formation ΔfHmo, ΔfSmo, and ΔfGmo for glycollide and 4-methylcyclohexene have also been evaluated at T = 298.15 K and po = 1.01325 × 105 Pa.

Thermodynamics of dl-lactide, polylactide and polymerization of dl-lactide in the range of 0–430K☆

Adiabatic and isothermal calorimetry were used for the first time to study thermodynamic properties of dl-lactide, polylactide and thermodynamic parameters of polymerization of dl-lactide. Specific heat C°p was measured with an accuracy of ∼0·2% in the range of 8–330°K and 0·7% in the range of 330–430°K. Functions of H°(T)−H°(0), S°(T), G°(T)−H°(0) of the monomer and polymer were calculated for the range of 0–430°K. Zero entropy S°c(0) of the polymer was determined in the glassy state. Combustion enthalpy values of the monomer and polymer were measured and standard parameters of the formation of these substances ΔH°f, ΔS°f and ΔG°f, calculated. From results obtained thermodynamic parameters of polymerization of lactide ΔH°p, ΔS°p and ΔG°p were alculated for the range of 0–430°K; the upper maximum temperature of polymerization T°u was established.

Thermodynamics of undecanolactone, tridecanolactone, and pentadecanolactone from 0 to 340 K

Abstract The heat capacities C p o of undercanolactone, tridecanolactone, and pentadecanolactone have been measured between 10 and 370 K in a vacuum adiabatic calorimetric cryostat within about 0.2 per cent. The temperatures and enthalpies of physical transitions have been also estimated. The enthalpies of combustion of the compounds have been measured in an isothermal calorimeter with an accuracy of 0.05 per cent. From the results the functions { H ( T ) − H (0)}, S o ( T ), and { G o ( T ) − H o (0)} have been calculated over the range 0 to 340 K, and the values of ΔH f o , ΔG f o and ΔS f o have been evaluated at T = 298.15 K.

The thermodynamics of glycollide, polyglycollide and of polymerization of glycollide in the temperature range of 0–550°K☆

The heat capacity C°p and the temperatures and enthalpies of the physical transitions of glycollide (GL) and polyglycollide (PGL) in the temperature range 13·8–550°K have been measured with a precision within 0·3–0·7%. The functions H°T−H°0, S°T and G°T−H°0 were calculated for GL in the crystalline and liquid states and for PGL in the crystalline, glassy, high-elastic and liquid states in the temperature region of 0–550°K. The zero entropy (S°0, C = 17 ± 2 J·mole−1·K−1) and the configurational entropy (S°conf = 18·8 J·mole−1·K−1) of PGL in the glassy state were determined. The vapour pressure of GL (modification kI) was measured, and ΔH°sub and ΔS°sub were calculated. ΔH°s of the monomer and polymer was determined in an isothermal bomb calorimeter. The standard values of ΔH°f, ΔS°f and ΔG°f of GL and PGL have been calculated. The thermodynamic characteristics ΔH°p, ΔS°p and ΔG, for the reaction GL → PGL, were calculated from the results oof the investigation. The strain in the six members, GL ring corresponds to Estr⋍31 kJ·mole−1.

Thermodynamics of allotropic modifications of carbon: Synthetic diamond, graphite, fullerene C60 and carbyne

Copyright (c) 1997 Elsevier Science B.V. All rights reserved. In an adiabatic vacuum calorimeter, a temperature dependence of heat capacity of four allotropic modifications of carbon, viz. synthetic diamond, graphite, carbyne and fullerene C 60 , has been studied in the (5-340) K range. The diamond sample studied is a commercial crystalline product containing impurities, according to a certificate, in an amount less than 1%; graphite is a spectrally pure crystalline substance with 99.9999 mass% of carbon; the carbyne sample with the content of carbon 99.5% is almost amorphous; crystalline fullerene C 60 has the content of a main substance ca. 99.98%. From the experimental data obtained for all objects under study, the thermodynamic functionsC 0 p ,H 0 (T)−H 0 (0), S 0 (T)and G 0 (T)−H 0 (0)have been calculated over the (0-340) K range. The calculation results and literature data on enthalpies of combustion have been used to calculate standard thermochemical parameters of formation Δ f H 0 , Δ f S 0 ,Δ f G 0 of synthetic diamond, fullerene C 60 and carbyne from graphite at T=298.15 Kand p=101.325 kPa. A comparison of thermodynamic properties of the allotropic carbon modifications has been made and the order of their thermodynamic stability has been found to be: carbyne (a)?graphite(cr)?diamond (cr)?fullerene C 60 (cr)

A calorimetric study of ethyl-α-cyanoacrylate and its polymerization and a study of polyethyl-α-cyanoacrylate at 13-450 K and normal pressure

Precision adiabatic and isothermal calorimetry have been used to study the following thermodynamic properties of ethyl-α-cyanoacrylate and its polymer: the isobaric heat capacity of the monomer in the region 13–330 K and that of the polymer in the region 13–450 K; the thermodynamic parameters of the monomers physical transition, the parameters of the polymers glass-transition and the glassy state and the combustion energy of the monomer and polymer. The following thermodynamic functions have been calculated: H0(T) − H0(0); S0(T), G0(I) − H0(0); ΔHcom0, δHf0, ΔSf0 and ΔGf0. The data obtained have been used to calculate values of the enthalpy, entropy and the Gibbs function for the polymerization of ethyl-α-cyanoacrylate in the temperature range 0–450 K and to assess the upper limiting temperature for this process.

Thermodynamic parameters of transformation of γ-butyrolactone into poly-γ-butyrolactone at normal pressure in the range of 0–400°K☆

A study was made using an adiabatic vacuum calorimeter of the specific heat of γ-butyrolactone (BL) and poly-γ-butyrolactone (PBL) in the range of 13·8–340°K an accuracy of ∼0·3%. Polymer glass temperature, melting point and melting enthalpy of monomers and polymers were measured. The combustion energy of BL and PBL was determined using an isothermal calorimeter. The following functions were calculated from results: H0(T)−H0(O), S0(T), G)(T)−H0(O) for the range of 0–330°K and ΔH0g, ΔH0f, ΔS0f, ΔG0f when T=298·15 °K and p=101·325 kPa. In the interval of 338–360°K the vapour pressure of BL was measured and values of ΔHi and ΔSi which are average values in the interval indicated, were evaluated. Thermodynamic parameters of BL→PBL transformation, ΔH0p, ΔS0p and ΔG0p were calculated for the 0–400°K range at normal pressure. As a result it was established that this process is thermodynamically prohibited under the physical conditions indicated.

Thermodynamics of polymerization of vinyltrimethylsilane

The thermodynamic parameters of the process vinyltrimethylsilane (VTMS)→→polyvinyltrimethylsilane (PVTMS) have been determined in the temperature region of 50–300°K. It was found that at 300°K ΔH0 = − 47·8 kcal/mole, ΔS0 = − 22·9 kcal/mole/deg and Δ0 = − 10·9 kcal/mole (VTMS-liquid, PVTMS-glassy state). The polymerization-depolymerization equilibrium constant K = 8·8 × 106 at the same temperature. The thermodynamic characteristics of VTMS and PVTMS were determined, namely Cp in the 60–300°K region, p (torr) = f(T) and the enthalpy of combustion of PVTMS (−1038·2±1·8 kcal/mole). HT0H00ST0 and GT0H00 in the region of 0–300°K have been calculated for the monomer and polymer.

Calorimetric study of ethylene oxalate, polyethylene oxalate and parameters of the polymerization of ethylene oxalate in the range 8–450 K☆

Thermodynamic characteristics of ethylene oxalate and polyethylene oxalate have been investigated in the range 8–450°K by precision adiabatic and isothermal calorimetry and by differential scanning microcalorimetry. Using the data obtained functions C°p(T), H°(T)−H°(0), S°(T) and G°(T)−H°(0) were calculated for the range 0–360°K, and ΔH°c, ΔH°f, ΔS°f and ΔG°f at T = 298·15°K and p =101·325 kPa. Thermodynamic parameters of the bulk polymerization of ethylene oxalate in the range 0–415°K were calculated, and the upper limiting temperature of the polymerization process was determined.

The calorimetric study in the 13·8–340°K range of δ-valerolactone, its polymer, and of the δ-valerolactone polymerization☆

Abstract Precision adiabatic and isothermal calorimetric methods have been used for the first time to study the thermodynamic properties of δ-valerolactone (VL), its polymer (PVL) and the thermodynamic parameters of the VL bulk polymerization. The heat contents C ° p of the monomer and polymer were determined with ∼0·3% precision, also the temperature and enthalpy of the physical transitions; the functions H ° ( T )− H ° (0), S ° ( T ) and G ° ( T )− H ° ()) have been calculated for the 0–350°K range. The S ° g (0), S ° er , H ° g (0)− H ° er (0) values of the PVL have been estimated in the glass-like state. The enthalpy of the VL→PVL process has been determined at 298·15°K and p = 101·325 kPa. The found values have been used to calculate the enthalpy, entropy and Gibbs energy of the VL polymerization and also the equilibrium concentration of the monomer in the reaction mass at normal pressure.