Glass Transition and Heat Capacities of Inorganic Glasses: Diminishing Change in the Heat Capacity at

2009 ◽  
pp. 185-185-17 ◽  
Author(s):  
J Kincs ◽  
J Cho ◽  
D Bloyer ◽  
SW Martin
Keyword(s):  
Heat Capacity ◽  
Glass Transition ◽  
Heat Capacities ◽  
Inorganic Glasses

Heat capacities and enthalpies of fusion and transformation for solvates of some salts with dimethyl sulfoxide and dimethylformamide

1988 ◽  
Vol 53 (12) ◽  
pp. 3072-3079
Author(s):  
Mojmír Skokánek ◽  
Ivo Sláma
Keyword(s):  
Heat Capacity ◽  
Phase Transformation ◽  
Phase Transformations ◽  
Dimethyl Sulfoxide ◽  
Liquidus Temperature ◽  
Molar Heat Capacity ◽  
Solid Phase ◽  
Zinc Nitrate ◽  
Heat Capacities ◽  
Liquid Phases

Molar heat capacities and molar enthalpies of fusion of the solvates Zn(NO3)2 . 2·24 DMSO, Zn(NO3)2 . 8·11 DMSO, Zn(NO3)2 . 6 DMSO, NaNO3 . 2·85 DMSO, and AgNO3 . DMF, where DMSO is dimethyl sulfoxide and DMF is dimethylformamide, have been determined over the temperature range 240 to 400 K. Endothermic peaks found for the zinc nitrate solvates below the liquidus temperature have been ascribed to solid phase transformations. The molar enthalpies of the solid phase transformations are close to 5 kJ mol-1 for all zinc nitrate solvates investigated. The dependence of the molar heat capacity on the temperature outside the phase transformation region can be described by a linear equation for both the solid and liquid phases.

SILICON-CONTAINING OLIGOMERIC AZOINITIATORS IN THE SYNTHESIS OF BLOCK COPOLYMERS

2021 ◽  
Vol 43 (2) ◽  
pp. 123-132
Author(s):  
N.A. Busko ◽  
◽  
V.K. Grishchenko ◽  
A.V. Barantsova ◽  
N.V. Gudzenko ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Block Copolymers ◽  
Ir Spectroscopy ◽  
Molar Ratio ◽  
Capacity Curves ◽  
Azo Initiator ◽  
Azo Initiators

The aim of the work was to develop methods for the synthesis and study of the properties of silicon-containing oligomeric azo- and polyazoinitiators based on bis-γ-hydroxypropylpolysiloxane (HPS) and bis-γ-aminopropylpolysiloxane (APS). Silicon-containing oligomeric azoinitiators using HPS were synthesized on the basis of cyclohexanone azo-bis-isobutyrohydrazone (AGN-CH) and bis-γ-hydroxypropylpolysiloxane bifunctional macrodiisocyanate (MDIHPS). MDIHPS was obtained by the interaction of GPS with 2,4 toluene diisocyanate (2,4-TDI). Oligomeric azoinitiators have been obtained, which have the structure RXR and (RX)nR, where R is a propylpolysiloxane block, X is a azo initiator block. For the synthesis of an oligomeric azo initiator based on bis-γ-aminopropyl polysiloxane (APS), a method was first developed for the synthesis of a monomeric azo initiator with terminal oxadiazolinylcarbamanate isocyanate groups (AGN-NCO) by the interaction of AGN-CH and 2,4-TDI at a molar ratio of 1: 2. On the basis of the obtained AGN-NCO and APS at a molar ratio of AGN-NCO: APS = 1: 1, an oligomeric azo initiator (OAI APS-P) was synthesized, which has the structure (RX)nR, where R is a propylpolysiloxane block, X is an azo initiator block. The structures of monomeric and oligomeric azo initiators have been studied by UV and IR spectroscopy, and the kinetic regularities of their synthesis have been calculated. On the basis of oligomeric azo initiators and styrene, block copolymers of the (AB)nA type were obtained by the method of thermal and photoinitiated radical polymerization, where A is a propylpolysiloxane block, B is an oligosyrene block with a constant value of the organosilicon block and a different size of the oligostyrene block. The structure of block copolymers was investigated by IR spectroscopy. It was shown that during photopolymerization, oligostyrene blocks of shorter length are formed than during thermopolymerization, and possible oxidation processes. The study of relaxation transitions by DSC in oligostyrene and propylpolysiloxane blocks of the BCP showed that the common heat capacity curves are the presence of two jumps in the heat capacity at the glass transition temperatures of the polysiloxane and oligostyrene microphase. A slight shift in the glass transition temperature of polysiloxane microphases in BCP towards higher temperatures compared to the homopolymer may be associated with the effect of oligostyrene microphase. With a decrease in the length of the oligosyrene block, a low-temperature shift in the glass transition temperature of oligostyrene blocks relative to the homopolymer and a depression of ∆Cp,2 are observed, which is associated with the suppression of mobility in oligodienic microphases by less mobile propylpolysiloxane blocks.

Glass transition in inorganic glasses, polymers, and crystals

1996 ◽  
Vol 176 (1) ◽  
pp. 25-32 ◽  
Author(s):  
A. Havránek ◽  
M. Marvan
Keyword(s):  
Glass Transition ◽  
Inorganic Glasses

Heat capacities at constant volume, free volumes, and rotational freedom in some liquids

1971 ◽  
Vol 24 (9) ◽  
pp. 1817 ◽  
Author(s):  
DD Deshpande ◽  
LG Bhatgadde
Keyword(s):  
Heat Capacity ◽  
Free Volume ◽  
Heat Capacities ◽  
Organic Liquids ◽  
Velocity Of Sound ◽  
Velocity Data ◽  
Volume Analysis ◽  
Straight Lines ◽  
Rotational Freedom ◽  
Residual Heat

This paper presents the experimental results on the velocity of sound, densities, and heat capacities of eight organic liquids at 25�, 35�, and 45�C. Using Eyring's equation, the free volumes have been calculated from the sound velocity data. For pure liquids, a quantity Cv* = (Cv)L- (Cv)g- Cstr called the residual heat capacity is found to be linearly dependent on free volume. Analysis of the data for 34 liquids shows that a plot of residual heat capacity against the free volume gives a series of straight lines differing in slopes for different groups of liquids such as hydrocarbons, halogen-substituted hydrocarbons, alcohols, etc. This behaviour is ascribed as being due to different degrees of rotational freedom of molecules in these liquids.

Nanocomposites Based on Hyperbranched Polymers and Montmorillonite

2011 ◽  
Vol 108 ◽  
pp. 91-94 ◽  
Author(s):  
Shao Jian He ◽  
Jun Lin
Keyword(s):  
Heat Capacity ◽  
Glass Transition ◽  
Full Range ◽  
Hyperbranched Polymers ◽  
Xrd Analysis ◽  
Rigid Amorphous Fraction ◽  
Two Phase ◽  
Heat Capacity Jump ◽  
Silicate Layers ◽  
Rigid Amorphous

Nanocomposites based on hyperbranched polymers and sodium montmorillonite were prepared over the full range of compositions. The XRD analysis showed the full exfoliation of silicate layers at lower silicate content (up to 9.1 wt%). With the further increase of silicate loading, an intercalated structure was developed with a constant d-spacing due to the unique structure of hyperbranched polymers. The heat capacity jump at the glass transition of the nanocomposites was found to deviate from the two-phase model prediction, indicating the formation of a rigid amorphous fraction. The glass transition temperature and heat capacity jump behaviors suggested that the molecular mobility of hyperbranched polymers were restricted by the introduction of silicate layers. The mechanical properties of the nanocomposites were also investigated.

scholarly journals Calculation of the Isobaric Heat Capacities of the Liquid and Solid Phase of Organic Compounds at 298.15K by Means of the Group-Additivity Method

Molecules ◽  
2020 ◽  
Vol 25 (5) ◽  
pp. 1147
Author(s):  
Rudolf Naef
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Goodness Of Fit ◽  
Cross Validation ◽  
Solid Phase ◽  
Linear Equations ◽  
Heat Capacities ◽  
Molecular Volume ◽  
Complementary Method ◽  
Standard Deviations

The calculation of the isobaric heat capacities of the liquid and solid phase of molecules at 298.15 K is presented, applying a universal computer algorithm based on the atom-groups additivity method, using refined atom groups. The atom groups are defined as the molecules’ constituting atoms and their immediate neighbourhood. In addition, the hydroxy group of alcohols are further subdivided to take account of the different intermolecular interactions of primary, secondary, and tertiary alcohols. The evaluation of the groups’ contributions has been carried out by solving a matrix of simultaneous linear equations by means of the iterative Gauss–Seidel balancing calculus using experimental data from literature. Plausibility has been tested immediately after each fitting calculation using a 10-fold cross-validation procedure. For the heat capacity of liquids, the respective goodness of fit of the direct (r2) and the cross-validation calculations (q2) of 0.998 and 0.9975, and the respective standard deviations of 8.24 and 9.19 J/mol/K, together with a mean absolute percentage deviation (MAPD) of 2.66%, based on the experimental data of 1111 compounds, proves the excellent predictive applicability of the present method. The statistical values for the heat capacity of solids are only slightly inferior: for r2 and q2, the respective values are 0.9915 and 0.9874, the respective standard deviations are 12.21 and 14.23 J/mol/K, and the MAPD is 4.74%, based on 734 solids. The predicted heat capacities for a series of liquid and solid compounds have been directly compared to those received by a complementary method based on the "true" molecular volume and their deviations have been elucidated.

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