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The present work presents an extensive literature survey and analysis of the heat capacity and thermodynamic properties of fusion, vaporization, and sublimation for the linear hydrocarbons and several terminally substituted homologous series. The successive introduction of methylene groups on the relative stability of the solid and liquid phases is analyzed and discussed based on the chain length dependence of the enthalpies, entropies, and Gibbs energies of phase transition. An odd–even alternation is observed in the fusion and sublimation equilibria. The improved packing patterns of even-numbered n-alkanes is reflected in higher values of melting temperatures and thermodynamic properties of phase transition. Molar heat capacities in liquid phase of n-alkanes derivatives exhibit a linear dependence with the chain length by an increment of 31 ± 2 J·K–1·mol–1 per methylene group (−CH2−). A contribution of 4.95 kJ·mol–1 per methylene group (value corrected for 298.15 K) is derived for the increment of the enthalpy of vaporization. A constant value for the specific enthalpy of vaporization is observed for long chain compounds: 360 J·g–1. As predictable, the enthalpy of vaporization is higher for groups that can form hydrogen-bonding interactions than for plain hydrocarbons. Concerning the monohalogenated alkanes, a clear increasing of enthalpy of vaporization for the larger halogen groups is observed. Moreover, the thermodynamic results indicate that along the fusion of n-alkanes and n-alkanols, there is a decrease of around 40% in the magnitude of intermolecular interactions.

In this work the description, test, and performance of a new vacuum apparatus for thin film vapor deposition (ThinFilmVD) of organic semiconductor materials are presented. The apparatus is able to fabricate single, multilayer/composites, or hybrid thin films using four independent, organic or inorganic, vapor deposition sources (Knudsen cells type), and the vapor mass flow is condensed onto a substrate surface (temperature regulated). The same apparatus could be also used to measure vapor pressures according to the Knudsen effusion methodology. Vapor pressures and thermodynamic properties of sublimation measured by Knudsen effusion of some reference organic materials (benzoic acid, anthracene, triphenylene, benzanthrone, 1,3,5-triphenylbenzene, perylene) were used to evaluate and test the performance of the apparatus. Moreover, nanostructures of thin films and composite materials of relevant charge transport and electroluminescent materials were deposited onto an indium−tin oxide (ITO) surface, and the morphology and thin film thickness were evaluated by scanning electron microscopy (SEM), exploring the effect of different mass flow rates and deposition time. The new physical vapor deposition apparatus based in four Knudsen effusion cells with an accurate mass flow control was designed to assemble well-defined (composition, morphology, thickness) thin films of organic semiconductors based on their volatility. The described apparatus presents a high versatility to the fabrication of single/multilayer thin films, as-grown crystals, and hybrid micro-and nanostructured materials.

The topographic structural analysis of thin films of triphenylamine (TPA) derivatives, obtained by vacuum deposition, is presented. The topology of the films is highly dependent on the number of phenyl rings as well on the presence of methyl groups. The glass transition temperatures can be predicted from the melting temperatures, according to the molecular symmetry, flexibility, and molecular size of the amorphous nonplanar materials suitable for long-time use in OLED based devices. A phase transition thermodynamics study, including vapor pressure and heat capacity determinations of some hole transport materials based triphenylamine derivatives (DDP, p-TTP, TPB, TPD, TDAB, and m-MTDAB) is presented. Analysis of the enthalpic and entropic contributions provides an understanding of the fusion temperature differentiation, which results in higher melting points for TDB and TDAB and lower values for TPD and m-MTDAB, due to the presence of meta-CH3 groups. The thermodynamic parameters of sublimation were used to explain the slightly higher volatility of solid DDP relative to p-TTP and the similarity between the volatilities of solids TPB and TDAB.

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