Thermodynamic properties of carbosilane dendrimers of the seventh and ninth generations with terminal butyl groups in the temperature range from <Emphasis Type="Italic">T</Emphasis> → 0 to 600 K

Temperature dependences of the heat capacity of carbosilane dendrimers with butyl terminal groups of the seventh and ninth generations were determined in the temperature range from 6 to 600 K by precision adiabatic vacuum calorimetry and differential scanning (dynamic) calorimetry. The physical transitions were revealed and their thermodynamic characteristics were analyzed. The experimental data obtained were used to calculate the standard thermodynamic functions C _p (T), H°(T) − H°(0), S°(T), and G°(T) − H°(0) for the temperature range from T → 0 to 600 K. The thermodynamic function-molar weight isotherms for the dendrimers of the third–ninth generations with terminal butyl groups in the glassy and highly elastic state are linear. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1924–1928, October, 2007.     

Carbosilane dendrimer of second generation with terminal methoxyundecylenate groups

The thermodynamic properties of carbosilane dendrimer of second generation with terminal methoxyundecylene groups were studied between 6 and 340 K by adiabatic vacuum calorimetry: the temperature dependence of the molar heat capacity C_p ⁰ was measured, the physical transformations were established and their thermodynamic characteristics were obtained. The experimental data were used to calculate the thermodynamic functions C_p ⁰ (T), H ⁰(T)-H ⁰(0), S⁰(T), G ⁰(T)-H ⁰(0) of the compound in the range 0 to 340 K. from the relation C_p ⁰ (T) the fractal dimension of the dendrimer was experimentally determined. The heat capacity of the dendrimer was compared with the corresponding additive values calculated from the properties of its constituents - a dendritic matrix (carbosilane dendrimer of second generation) and the corresponding amount of moles of methyl ester of 11-(tetramethyldisiloxy)undecanoic acid serving as terminal groups. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermodynamic properties of a liquid crystal carbosilane dendrimer

The temperature dependence of the heat capacity of a first-generation liquid crystal carbosilane dendrimer with methoxyphenyl benzoate end groups is studied for the first time in the region of 6–370 K by means of precision adiabatic vacuum calorimetry. Physical transformations are observed in this interval of temperatures, and their standard thermodynamic characteristics are determined and discussed. Standard thermodynamic functions C_p^°(T), H°(T) ? H°(0), S°(T) ? S°(0), and G°(T) ? H°(0) are calculated from the obtained experimental data for the region of Т → 0 to 370 K. The standard entropy of formation of the dendrimer in the partially crystalline state at Т = 298.15 K is calculated, and the standard entropy of the hypothetic reaction of its synthesis at this temperature is estimated. The thermodynamic properties of the studied dendrimer are compared to those of second- and fourth-generation liquid crystal carbosilane dendrimers with the same end groups studied earlier.     

Thermodynamic properties of poly[<Emphasis Type="Italic">bis</Emphasis>(trifluoroethoxy) phosphazene] in the range from <Emphasis Type="Italic">T</Emphasis>→0 TO 620 K

By adiabatic vacuum and dynamic calorimetry, heat capacity for poly[bis(trifluoroethoxy)phosphazene] has been determined over the 6–620 K range. Physical transformations of the polymer on its heating and cooling have been detected and characterized. Smoothed heat capacity C _p⁰(T) and standard thermodynamic functions (H ⁰(T)-H ⁰(0), S ⁰(T) and G ⁰(T)-H ⁰(0)) of poly[bis(trifluoroethoxy)phosphazene] have been evaluated for the temperature range from T→0 to 560 K. The standard entropy of formation Δ_f S ⁰ at T=298.15 K has been also determined. Fractal dimensions D in the heat capacity function of the multifractal variant of Debye’s theory of heat capacity of solids characterizing the heterodynamics of the tested polymer have been determined.     

Thermodynamic properties of linear polyurethanes based on 1,6-hexamethylenediisocyanate with butane-1,4-diol and hexane-1,6-diol in the temperature range from T → 0 to 460 K

The temperature dependences of the heat capacity of partially crystalline linear polyurethanes based on 1,6-hexamethylenediisocyanate with butane-1,4-diol and hexane-1,6-diol were studied for the first time in a temperature range of 6–460 K by the methods of adiabatic vacuum and dynamic calorimetry. Physical changes in the state of polyurethanes were revealed and characterized; the standard thermodynamic functions, namely, C _p °(T), H°(T)-H°(0), S°(T), and G°(T)-H°(0), were calculated from the obtained experimental data in the temperature range from T → 0 to 460 K for the polymers in the crystalline, glassy, highly elastic, and liquid states. The energies of combustion of the polymers were measured by the bomb calorimetry method, and the standard thermodynamic characteristics of their formation at 298.15 K were calculated. The thermodynamic characteristics of bulk polycondensation of 1,6-hexamethylenediisocyanate with butane-1,4-diol and hexane-1,6-diol to form linear aliphatic polyurethanes-{4,6} and-{6,6} were determined in the range from T → 0 to 350 K at p° = 0.1 MPa. The thermodynamic properties of the polyurethanes under study and polymers of isomeric structure were compared. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 817–823, May, 2006.     

The thermodynamic properties of 2-ethylhexyl acrylate over the temperature range from <Emphasis Type="Italic">T</Emphasis> → 0 to 350 K

The temperature dependence of the heat capacity C _p ^o= f(T) 2 of 2-ethylhexyl acrylate was studied in an adiabatic vacuum calorimeter over the temperature range 6–350 K. Measurement errors were mainly of 0.2%. Glass formation and vitreous state parameters were determined. An isothermic shell calorimeter with a static bomb was used to measure the energy of combustion of 2-ethylhexyl acrylate. The experimental data were used to calculate the standard thermodynamic functions C _p ^o(T), H ^o(T)-H ^o(0), S ^o(T)-S ^o(0), and G ^o(T)-H ^o(0) of the compound in the vitreous and liquid states over the temperature range from T → 0 to 350 K, the standard enthalpies of combustion Δ_c H ^o, and the thermodynamic characteristics of formation Δ_f H ^o, Δ_f S ^o, and Δ_f G ^o at 298.15 K and p = 0.1 MPa.     

Low-temperature thermodynamic properties of <Emphasis Type="Italic">L</Emphasis>-cysteine

Heat capacity C _p(T) of the orthorhombic polymorph of L-cysteine was measured in the temperature range 6–300 K by adiabatic calorimetry; thermodynamic functions were calculated based on these measurements. At 298.15 K the values of heat capacity, C _p; entropy, S _m⁰(T)-S _m⁰(0); difference in the enthalpy, H _m⁰(T)-H _m⁰(0), are equal, respectively, to 144.6±0.3 J K⁻¹ mol⁻¹, 169.0±0.4 J K⁻¹ mol⁻¹ and 24960±50 J mol⁻¹. An anomaly of heat capacity near 70 K was registered as a small, 3–5% height, diffuse ‘jump’ accompanied by the substantial increase in the thermal relaxation time. The shape of the anomaly is sensitive to thermal pre-history of the sample.     

Thermodynamics of phenylated polyphenylene between 0 and 340 K

In an adiabatic vacuum calorimeter, the temperature dependence of the heat capacity C _p of phenylated polyphenylene and initial comonomer 1,4-bis(2,4,5-triphenylcyclopentadienone-3-yl)benzene was studied between 6 and 340 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield their energies of combustion DUcomb were measured. From the experimental data, the thermodynamic functions C _p ⁰ (T), H ⁰(T)-H ⁰(0), S ⁰(T)-S⁰(0), G ⁰(T)-H ⁰(0) were calculated from 0 to 340 K, and standard enthalpies of combustion ΔH _comb ⁰ and thermodynamic parameters of formation-enthalpies ΔH _f ⁰, entropies ΔH _f ⁰, Gibbs functions ΔG _f ⁰ - of the substances studied were estimated at T=298.15 K at standard pressure. The results were used to calculate the thermodynamic characteristics (ΔH _f ⁰ ,ΔS _f ⁰, ΔG _f ⁰) of phenylated polyphenylene synthesis in the range from 0 to 340 K. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermodynamics of C70 fullerence in the 0–390 K temperature range

The temperature dependence of heat capacity of C₇₀ fullerene was studied by calorimetry in the range between 6 and 390 K. Phase transitions were established and their thermodynamic characteristics were determined. From the experimental data obtained, the thermodynamic functionsH ^o (T)-H ^o(0),S ^o(T),G ^o(T)-H ^o(0) for temperatures between 0 and 390 K were calculated. The results were used to calculate the standard values of Δ_f S ^o, Δ_f G ^o, and logK _f ^o for the formation of C₇₀ from graphite. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 647–650, April, 1998.     

Thermodynamic properties of the first to fifth generations of carbosilane dendrimers with allyl terminal groups

Temperature dependences of the specific heats, characteristic temperatures, and enthalpies of physical transformations of the first to fifth generations of carbosilane dendrimers with allyl terminal groups were studied using an adiabatic vacuum calorimeter in the temperature range 6—340 K. The error of measurements was, as a rule, about 0.2%. Thermodynamic characteristics of physical transformations of the dendrimers were determined and their thermodynamic functions C _p°(T), H°(T)—H°(0), S°(T)—S°(0), and G°(T)—H°(0) were calculated for the temperature range 0—340 K. The thermodynamic functions of the dendrimers are linearly related to their molecular weights, the number of allyl groups on their outer spheres, and the number of moles of diallylmethylsilane per mole of the dendrimers formed. Additive dependence of the properties of the dendrimers on their chemical composition and structure indicates that the energy of interaction between structural fragments of the dendrimers is independent of the dendrimer generation number. The fractal dimensions, D, of all dendrimers studied in this work are 1.2—1.3 in the temperature range 30—50 K, thus indicating a chain-layered structure of the dendrimer glasses.     

The thermodynamic properties of (2,2′-dipyridyl)bis(4-chloro-3,6-di-tert-butyl-<Emphasis Type="Italic">o</Emphasis>-benzosemiquinone)cobalt

The heat capacity of paramagnetic (2,2′-dipyridyl)bis(4-chloro-3,6-di-tert-butyl-o-benzosemi-quinone)cobalt was studied over the temperature range 8–390 K by precision adiabatic vacuum and high-accuracy dynamic calorimetry. The physical transformation observed at 309–388 K was caused by the transition of the semiquinone-catecholate to bis-semiquinone form of the complex. Above 388 K, thermal destruction was superimposed on the physical transition. The experimental data were used to calculate the standard thermodynamic functions C _p ^o (T), H ^o(T)−H ^o(0), S ^o(T), and G ^o(T)−H ^o(0) at temperatures from T → 0 to 300 K. An analysis of the low-temperature heat capacity of the complex in terms of the Debye theory of the heat capacity of solids and its multifractal generalization led us to conclude that the complex had a predominantly chain structure.     

Thermodynamics of fluorinated derivatives of carbosilane dendrimers of high generations

The temperature dependences of the heat capacities of fluorinated derivatives of carbosilane dendrimers of high (4.5 and 7.5) generations were studied by adiabatic vacuum calorimetry in the range from 6 to 340 K for the first time. The standard thermodynamic characteristics of devitrification were estimated. The experimental results were used to calculate the standard thermodynamic functions C _p °(T), H°(T)?H°(0), S°(T)?S°(0), and G°(T)-H°(0) over the range from T??0 to 340 K and standard entropies of formation of dendrimers at T = 298.15 K. The low-temperature (T ?? 50 K) heat capacity was analyzed by using Debye??s heat capacity theory of solids and the multifractal model. The values of fractal dimensionality D were determined, and some conclusions about topology of the studied structures were made. The standard thermodynamic characteristics of the studied fluorinated derivatives of carbosilane dendrimers were compared.     

Thermodynamic characteristics of hydrated acrylamide and polyacrylamide complexes of cobalt nitrate at <Emphasis Type="Italic">T</Emphasis> → 0 to 380 K

The temperature dependences of the heat capacities of hydrated acrylamide and poly(acrylamide) complexes of cobalt nitrate are studied via high-precision adiabatic calorimetry at 6 to 300–380 K. The energy of combustion is estimated via isothermic calorimetry. This evidence makes it possible to calculate thermodynamic functions C _p ^ℴ(T), H ^ℴ(T) − H ^ℴ(0), S ^ℴ(T), G ^ℴ(T) − H ^ℴ(0) at 0 to 300–380 K; the standard enthalpy of combustion, ΔcH ^ℴ; and the thermodynamic parameters of formation, Δ _f H ^ℴ, Δ _f S ^ℴ, and Δ _f G ^ℴ, of monomer and polymer complexes composed of simple compounds at 298.15 K. The results are used for the estimation of enthalpy Δ_pol H ^ℴ, entropy Δ_pol S ^ℴ, and Gibbs function Δ_pol G ^ℴ of bulk polymerization for hydrated acrylamide complexes of cobalt nitrate at 0–300 K.     

Thermodynamic Properties of a First-Generation Carbosilane Dendrimer with Terminal Phenylethyl Groups

The heat capacity of a first-generation carbosilane dendrimer with terminal phenylethyl groups as a function of temperature in the range from 6 to 520 K is studied for the first time via precision adiabatic vacuum calorimetry and differential scanning calorimetry. Physical transformations, such as low-temperature structural anomaly and glass transition are detected in the above-mentioned range of temperatures, and their standard thermodynamic characteristics are determined and analyzed. The standard thermodynamic functions of the studied dendrimer in the range of T → 0 to 520 K are calculated from the experimental data, as is the standard entropy in the devitrified state at T = 298.15 K. The standard thermodynamic characteristics of the carbosilane dendrimers studied in this work and earlier are compared.     

Thermodynamic properties of first- and third-generation carbosilane dendrimers with terminal phenyldioxolane groups

The heat capacities of first- and third-generation carbosilane dendrimers with terminal phenyldioxolane groups are studied as a function of temperature via vacuum and differential scanning calorimetry in the range of 6 to 520 K. Physical transformations that occur in the above temperature range are detected and their standard thermodynamic characteristics are determined and analyzed. Standard thermodynamic functions C_p^ο(T), [H°(T) ? H°(0)], [S°(T) ? S°(0)], and [G°(T) ? H°(0)] in the temperature range of T → 0 to 520 K for different physical states and the standard entropies of formation of the studied dendrimers at T = 298.15 K are calculated, based on the obtained experimental data.     

Thermodynamics of tetraphenylantimony acetophenoneoxymate

In the present research for the first time, the heat capacity C_\textp ^° C_{\text{p}}^{ \circ } of crystalline tetraphenylantimony acetophenoneoxymate Ph₄SbONCPhMe has been measured using the methods of precision adiabatic vacuum calorimetry over the range from 6 to 350 K, the standard thermodynamic functions: heat capacity C_\textp ^° (T ) C_{\text{p}}^{ \circ } (T ) , enthalpy H°(T) − H°(0), entropy S°(T), and Gibbs function G°(T) − H°(0) have been calculated over the range from T → 0 K to 350 K. Low-temperature (20 K ≤ T ≤ 50 K) heat capacity data have shown a chain-layered structure topology of the compound under study. The energy of combustion of the compound has been determined in the isothermal combustion calorimeter with a stationary bomb. The standard thermodynamic functions of formation of crystalline Ph₄SbONCPhMe at 298.15 K have been calculated. The differential scanning calorimetry and thermogravimetric analysis studies have shown the compound melts with decomposition and its melting temperature has been estimated. Thermodynamic properties of Ph₄SbONCPhMe, Ph₅Sb and Ph₄SbONCPh₂ have been compared.     

The thermodynamic functions of fullerene derivative (<Emphasis Type="Italic">t</Emphasis>-Bu)<Subscript>12</Subscript>C<Subscript>60</Subscript> over the temperature range from <Emphasis Type="Italic">T</Emphasis> → 0 to 420 K

The temperature dependence of heat capacity C _p ^o = f(T) of fullerene derivative (t-Bu)₁₂C₆₀ has been measured by a adiabatic vacuum calorimeter over the temperature range T = 6–350 K and by a differential scanning calorimeter over the temperature range T = 330–420 K for the first time. The low-temperature (T ≤ 50 K) dependence of the heat capacity was analyzed based on Debye’s the heat capacity theory of solids and its fractal variant. As a consequence, the conclusion about structure heterodynamicity is given. The experimental results have been used to calculate the standard thermodynamic functions C _p ^o (T), H ^o(T)−H ^o(0), S ^o(T) and G ^o(T) − H ^o(0) over the range from T → 0 to 420 K. The standard entropy of formation at 298.15 K of fullerene derivative under study was calculated. The temperature of decomposition onset of derivative was determined by differential scanning calorimetery and thermogravimetric analysis. The standard thermodynamic characteristics of (t-Bu)₁₂C₆₀ and C₆₀ fullerite were compared.     

Thermodynamic properties of carbosilane dendrimers of the third and sixth generations with ethyleneoxide terminal groups

The temperature dependences of the heat capacities of carbosilane dendrimers of the third and sixth generations with ethyleneoxide terminal groups are examined for the first time by means of precision adiabatic vacuum calorimetry at temperatures between 6.5 and 350 K. In this temperature range, physical transformations are observed and their standard thermodynamic characteristics are determined and discussed. The standard thermodynamic functions are calculated per nominal mole of a chosen unit using the obtained experimental data: C° _p (T), H°(T) - H°(0), S°(T) - S°(0), and G°(T) - H°(0) in the interval T → 0 to 350 K, and the standard entropies of formation at T = 298.15 K. The low-temperature (T ≤ 50 K) heat capacity is analyzed using the Debye theory of specific heat and a multifractal model. The values of fractal dimension D are also determined, and conclusions on the investigated structures’ topology are drawn. The corresponding thermodynamic properties of the studied dendrimers are compared as well.     

Low-temperature heat capacity and standard entropy of PdO(cr.)

The temperature dependence of the heat capacity C _p ^o = f(T) of palladium oxide PdO(cr.) was studied for the first time in an adiabatic vacuum calorimeter in the range of 6.48–328.86 K. Standard thermodynamic functions C _p ^o(T), H ^o(T) — H ^o(0), S ^o(T), and G ^o(T) — H ^o(0) in the range of T → 0 to 330 K (key quantities in different thermodynamic calculations with the participation of palladium compounds) were calculated on the basis of the experimental data. Based on an analysis of studies on determining the thermodynamic properties of PdO(cr.), the following values of absolute entropy, standard enthalpy, and Gibbs function of the formation of palladium oxide are recommended: S ^o(298.15) = 39.58 ± 0.15 J/(K mol), Δ_f H ^o(298.15) = −112.69 ± 0.32 kJ/mol, Δ_f G ^o(298.15) = −82.68 ± 0.35 kJ/mol. The stability of Pd(OH)₂ (amorph.) with respect to PdO(cr.) was estimated.     

Thermodynamics of a third-generation poly(phenylene-pyridyl) dendron decorated with dodecyl groups in the range of <Emphasis Type="Italic">T</Emphasis> → 0 to 480 K

The heat capacity of a glassy third-generation poly(phenylene-pyridyl) dendron decorated with dodecyl groups is studied for the first time via high-precision adiabatic vacuum and differential scanning calorimetry in the temperature range of 6 to 520 K. The standard thermodynamic functions (molar heat capacity C_p^°, enthalpy H°(T), entropy S°(T), and Gibbs energy G°(T)-H°(0)) in the range of T → 0 to 480 K, and the entropy of formation at 298.15 K, are calculated on the basis of the obtained data. The thermodynamic properties of the dendron and the corresponding third-generation poly(phenylene-pyridyl) dendrimer studied earlier are compared.