Inclusion compounds thermal stability

Table 1. Clathrate inclusion compounds of I stoichiometries and thermal stability characterization...

Selectivity at formation of a respective inclusion compound and its thermal stability behavior might differ (cf. Tables 1 and 2), since for both representations different processes should be taken into consideration. Formation of a crystal inclusion compound is normally controlled by kinetics, whereas the thermal stability (decomposition property) is a result of thermodynamics. Thus, we speak of formation selectivity , on the one hand, and of binding selectivity , on the other. 

Considering this variety of crystalline inclusion compounds, 26 is close to 1 (cf. Table 1) and like 1, the stoichiometries (host guest) found for the different aggregates of 26 largely correspond to the expected ratios. Thermal stabilities in most cases are relatively high. 

Direct insertion probe pyrolysis mass spectrometry (DPMS) utilises a device for introducing a single sample of a solid or liquid, usually contained in a quartz or other non-reactive sample holder, into a mass spectrometer ion source. A direct insertion probe consists of a shaft having a sample holder at one end [70] the probe is inserted through a vacuum lock to place the sample holder near to the ion source of the mass spectrometer. The sample is vaporized by heat from the ion source or by heat from a separate heater that surrounds the sample holder. Sample molecules are evaporated into the ion source where they are then ionized as gas-phase molecules. In a recent study, Uyar et al. [74] used such a device for studying the thermal stability of coalesced polymers of polycarbonate, PMMA and polylvinyl acetate) (PVAc) [75] and their binary and ternary blends [74] obtained from their preparation as inclusion compounds in cyclodextrins. 

The inclusion of heat stabilizers is essential to protect the system against thermal decomposition at elevated temperatures during processing. For this purpose, tin carboxylate esters or liquid calcium-zinc stabilizers are preferred. Thio-tin compounds are very effective as heat stabilizers but must be regarded with caution, bearing in mind that they can lead to unpleasant and unacceptable residual odours. Secondary stabilizers that can be used include epox-idized soya bean oil. 

Many carbene complexes, especially those bearing one or two hydrogen substituents, are thermally unstable with respect to the formation of alkenes or their complexes (Figure 5.13), usually via bimolecular intermediates. For this reason the thermal stability of carbene complexes can normally be enhanced by inclusion of sterically demanding co-ligands. Often within a triad the stability of carbene complexes increases in the order 4d < 3d < 5d when analogous compounds can be obtained and compared. 

Low-temperature synthesis. Due to the homogeneity of the dried powder/gel product and the smaller particle size when compared to grind-and-fire methods, nucleation and growth of crystalline phases can occur at lower temperatures. This also allows the synthesis of metastable phases and the inclusion of organic or other compounds with low thermal stability into the final product. Volatile materials are no longer lost and amorphous phases can be formed. Lower temperatures avoid the effects of particle sintering. 

Inclusion Compounds Selectivity, Thermal Stability, o7d Kinetics, p. 696 Macrocye Synthesis, p. 830... 

Inclusion Compounds Selectivity, Thermal Stability, and Kinetics, p. 696 Induced Fit. p. lYl Kinetics of Complexation, p. 774 Macrocycle Synthesis, p. 830 The Template Effect, p. 1493... 

Inclusion Compounds Selectivity, Thermal Stability, and Kinetics... 

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