Vapor Sublimation Research Articles

Health is the greatest wealth: Quest for a diagnostic check for thermochemistry of pure drug compounds

The development of pharmaceutical formulations and the optimisation of drug synthesis are not possible without knowledge of thermodynamics. At the same time, the quantity and quality of the available data is not at a level that meets modern requirements. A convenient diagnostic approach is desirable to assess the quality of available experimental thermodynamic data of drugs. A comprehensive set of available data on phase transitions of profens family drugs was analysed using new complementary measurements and structure–property correlations. The consistent sets of solid–gas, liquid–gas and solid–liquid phase transitions were evaluated for twelve active pharmaceutical ingredients based on alkanoic acid derivatives and recommended for the calculations of the pharmaceutical processes. A “centerpiece approach” proposed in this work helped to perform the “health check” of the thermochemical data. The evaluated data on the sublimation enthalpies were used to derive the crystal lattice energies of the profens and to correlate the water solubilities with the sublimation vapour pressures and molecular parameters. A “paper-and-pen” approach proposed in this work can be extended to the diagnosis of “sick” or “healthy” thermodynamic data for drugs with a different structure than those studied in this work.

Vapor Sublimation and Deposition Polymerization to Fabricate a Directional Scaffold for Guiding Tubular Dentin Regeneration

AbstractDental caries, or tooth decay, is a widespread problem and is generally considered irreversible, yet a regeneration solution exists to cure them. In this study, a multifunctional and biocompatible dental scaffold is fabricated by a unique vapor sublimation and deposition polymerization process with the well‐accepted material Parylene, resulting in the construction of a 3D and porous polymer scaffold that accommodates living cells and a combination of growth factor molecules in a single fabrication process, which differentiates the coating formation from a conventional vapor process. Physically, a directional interior structure is constructed to guide dental pulp stem cells (DPSCs) attachment and alignment. Biochemically, necessary growth factors, including Wnt‐3a and FGF‐2, are incorporated within the scaffold during fabrication to guide the cell differentiation of odontogenesis. The synergistic effects of the attachment and alignment of DPSCs, as well as the biocompatibility and odontogenic activities of the components accommodated in the scaffold, result in the upregulation of the cell differentiation into odontoblasts, as shown by the morphology of odontoblasts and the expressions of odontogenesis markers. Thus, the reported fabrication technique and its products represent an alternative approach for dentin regeneration in dental caries and tooth decay.

Controlling Superhydrophobicity on Complex Substrates Based on a Vapor-Phase Sublimation and Deposition Polymerization.

The superhydrophobic properties of material surfaces have attracted significant research and practical development in a wide range of applications. In the present study, a superhydrophobic coating was fabricated using a vapor-phase sublimation and deposition process. This process offers several advantages, including a controllable and tunable superhydrophobic property, a dry and solvent-free process that uses well-defined water/ice templates during fabrication, and a coating technology that is applicable to various substrates, regardless of their dimensions or complex geometric configurations. The fabrication process exploits time-dependent condensation to produce ice templates with a controlled surface morphology and roughness. The templates are sacrificed via vapor sublimation, which results in mass transfer of water vapor out of the system. A second vapor source of a polymer precursor is then introduced to the system, and deposition occurs upon polymerization on the iced templates, replicating the same topologies from the iced templates. The continuation of the co-current sublimation and deposition processes finally renders permanent hierarchical structures of the polymer coatings that combine the native hydrophobic property of the polymer and the structured property by the sacrificed ice templates, achieving a level of superhydrophobicity that is tunable from 90° to 164°. The experiments demonstrated the use of [2,2]paracyclophanes as the starting materials for forming the superhydrophobic coatings of poly(p-xylylenes) on substrate surfaces. In comparison to conventional vapor deposition of poly(p-xylylenes), which resulted in dense thin-film coatings with only a moderate water contact angle of approximately 90°, the reported superhydrophobic coatings and fabrication process can achieve a high water contact angle of 164°. Demonstrations furthermore revealed that the proposed coatings are durable while maintaining superhydrophobicity on various substrates, including an intraocular lens and a cardiovascular stent, even against harsh treatment conditions and varied solution compositions used on the substrates.

Theoretical Prediction of the Sublimation Behavior by Combining Ab Initio Calculations with Statistical Mechanics

We develop a theoretical model to predict the sublimation vapor pressure of pure substances. Moreover, we present a simple monoatomic molecule approximation, which reduces the complexity of the vapor pressure expression for polyatomic gaseous molecules at a convincing level of accuracy, with deviations of the Arrhenius prefactor for NaCl and NaF being 5.02% and 7.08%, respectively. The physical model is based on ab initio calculations, statistical mechanics, and thermodynamics. We illustrate the approach for Ni, Cr, Cu (metallic bond), NaCl, NaF, ZrO2 (ionic bond) and SiO2 (covalent bond). The results are compared against thermodynamic databases, which show high accuracy of our theoretical predictions, and the deviations of the predicted sublimation enthalpy are typically below 10%, for Cu even only 0.1%. Furthermore, the partial pressures caused by gas phase reactions are also explored, showing good agreement with experimental results.

Carbon ion self–sputtering attained by sublimation of hot graphite target and controlled by pulse injection of a neon–helium gas mixture

The operation of graphite targets with an increased temperature (HT – hot target) is studied for the case of gas injection magnetron sputtering (GIMS) of: 1) diamond–like carbon (DLC), and 2) carbon–silicon carbide (C–SiC) films. A purposely–thinned graphite target with a reduced thermal conductivity is applied for DLC deposition, extending its high temperature sputtering range up to 1636 °C. For the purpose of C–SiC synthesis four sockets with a silicon carbide powder are designed within graphite target. In this approach, the C–SiC target surface can be heated up to 1443 °C due to a greater energy input from impulse plasma, in the range 322–932 J. The HT sputtering is energy–controlled by a pulsed injection of a neon–helium gas mixture. High–energy Ne+ and He+ ions extend the length of pulsed GIMS discharge due to the self–sputtering effect observed during the deposition of DLC and C–SiC films. These conditions result in an almost 5–fold increase in the film growth rate (up to 185 nm/min) with respect to the operation with a cold target, which is due to the assisting vapour sublimation from custom–designed graphite–based targets. The temperature boosted HT GIMS discharge, proves to be an efficient tool for reaching relatively high (∼35 %) sp3–hybridized C content in both carbon–based materials. It also allows for tailoring the energy bandgap of DLC–based optical structure, in the range from 1.7 to 2.75 eV, due to the formation of the (CC) and (CO) bonds. Higher content of silicon oxide (SiO2-x) and silicon carbide (SiC) phases (15 – 23 %) in the case of C–SiC films results in hardness increase from 21.8 to 30.1 GPa.

Phase Transitions Equilibria of Five Dichlorinated Substituted Benzenes.

This work reports an experimental study aiming to determine the thermodynamic properties of five chlorinated compounds with environmental impact. The vapor pressures of the crystalline phases of three isomers of dichlorobenzoic acid (2,4-, 2,5-, and 2,6-) and 2,6-dichlorobenzonitrile were measured at several temperatures using the Knudsen effusion technique. Another technique (a static method based on capacitance diaphragm manometers) allowed the measurement of the vapor pressures of both the crystalline and liquid phases of 2,4-dichlorobenzonitrile between 303.0 and 380.0 K. This latter technique also enabled the measurement of sublimation vapor pressures of 2,6-dichlorobenzonitrile over a larger range interval of temperatures, T = 328.7 and 391.8 K. The standard molar enthalpy, entropy, and Gibbs energy of sublimation (for all the compounds studied) and vaporization (for 2,4-dichlorobenzonitrile) were derived, at reference temperatures, from the experimental vapor pressure results. The temperatures and enthalpies of fusion and the isobaric heat capacities of the five crystalline-substituted benzenes were determined using differential scanning calorimetry. The contributions of the three substituents (-COOH, -CN, and -Cl) to the sublimation thermodynamic properties of the compounds studied were discussed.

Controlling the asymmetry of densified and porous hybrid coatings based on vapor sublimation and deposition

Interface coating technology is important to render altered surface properties for materials while replacing undesired original properties. We herein introduce an asymmetric and hybrid coating comprising controlled structural and chemical properties in one coating layer synthesized in simple steps by a vapor-phase sublimation and deposition process. The synthesis of the hybrid coating is based on acknowledging that the adsorption-limited and diffusion-limited polymerization of poly (p-chloro-xylylene) is shown to vary the final coating form factor into a densified thin film and porous structure of poly (p-chloro-xylylene), respectively. The current study enables the manipulation of the two mechanisms at the solid/vapor interface by utilizing ice templates on material substrates with confined and designable configurations as well as locations, and the proposed fabrication process produces asymmetric and hybrid coatings in one transformation step from the arranged ice templates to the substrates. Demonstrations of such advanced hybrid coatings include side-by-side and/or layer-by-layer arrangement of dense/porous films of poly (p-chloro-xylylene) in horizontal and vertical layouts, as well as particulate and organized structural configurations to address the dense/porous combination, and finally, combined structural and chemical properties with define compartments in one coating layer. Most importantly, these hybrid coatings are synthesized utilizing simple mechanisms in simple steps regardless of the complication of the design of the asymmetry configuration, and the fabrication process uses environmentally-friendly water as a template together with the subsequent dry and clean vapor-phase sublimation and deposition process, in which no solvent, initiator, or catalyst is needed. The proposed hybrid coating technology is expected to attract unlimited applications across multidisciplinary fields in materials science.

Study on the volatility of four benzaldehydes

This work reports the experimental determination of relevant thermodynamic properties of four benzaldehydes. The vapor pressures of both crystalline and liquid phases (including supercooled liquid) of syringaldehyde, 3,4,5-trimethoxybenzaldehyde, 4-(dimethylamino)benzaldehyde and of the liquid phase of veratraldehyde were determined using a static method based on capacitance diaphragm manometers. Additionally, the sublimation vapor pressures of the four compounds were also determined at different temperatures, using the Knudsen mass-loss effusion method. The experimental results allowed accurate determination of the standard molar enthalpies, entropies and Gibbs energies of sublimation and of vaporization for the benzaldehydes studied, at reference temperatures, allowing phase diagram representations of the (p,T) results, in the neighborhood of the triple point of the four compounds. Their temperatures and molar enthalpies of fusion were determined using differential scanning calorimetry and were compared with the ones obtained indirectly through vapor pressure measurements. Using high-precision drop calorimetry, the standard isobaric molar heat capacities of the four crystalline benzaldehydes were determined at 298.15 K. The enthalpy of the intermolecular hydrogen bond OH…O in the crystalline phase of syringaldehyde was estimated.

Ice-templated synthesis of multicomponent porous coatings via vapour sublimation and deposition polymerization.

A multicomponent vapour-deposited porous (MVP) coating with combined physical and biochemical properties was fabricated based on a chemical vapour sublimation and deposition process. Multiple components are used based on their natural thermodynamic properties, being volatile and/or nonvolatile, resulting in the sublimation of water vapour (from an iced template), and a simultaneous deposition process of poly-p-xylylene occurs upon radical polymerization into a disordered structure, forming porous coatings of MVP on various substrates. In terms of physical properties, the coating technology exhibits adjustable hydrophobicity by tuning the surface morphology by timed control of the sublimation of the iced template layer from a substrate. However, by using a nonvolatile solution during fabrication, an impregnation process of the deposited poly-p-xylylene on such a solution with tuning contact angles produces an MVP coating with a customizable elastic modulus based on deformation-elasticity theory. Moreover, patterning physical structures with adjustable pore size and/or porosity of the coatings, as well as modulation and compartmentalization to introduce necessary boundaries of microstructures within one MVP coating layer, can be achieved during the proposed fabrication process. Finally, with a combination of defined solutions comprised of both volatile and nonvolatile multicomponents, including functional biomolecules, growth factor proteins, and living cells, the fabrication of the resultant MVP coating serves devised purposes exhibiting a variety of biological functions demonstrated with versatility for cell proliferation, osteogenesis, adipogenesis, odontogenesis, spheroid growth of stem cells, and a complex coculture system towards angiogenesis. Multicomponent porous coating technology is produced based on vapour sublimation and deposition upon radical polymerization that overturns conventional vapour-deposited coatings, resulting in only dense thin films, and in addition, the versatility of adjusting coating physical and chemical properties by exploiting the volatility mechanism of iced solution templates and accommodation of solute substances during the fabrication process. The MVP coating and the proposed fabrication technique represent a simple approach to provide a prospective interface coating layer for materials science and are attractive for unlimited applications.

Preparation and characterization of quarter-wave plate at 12.4 μm based on CdSe single crystal

CdSe single crystal with good optic properties is great candidates for optical devices. In this paper, CdSe single crystal was grown by the modified vertical unseeded vapor sublimation method with the diameter of 36 mm and the length of 40 mm. The quarter wave plates of CdSe single crystal with size of 20 mm × 20 mm × 3 mm was cut along the (001) orientation. The transmittance of the CdSe wave plate was about 69% in the range of 8–14 μm, where the absorption coefficient was about 0.04 cm−1. The phase delay was 90.71176° at 12.4 μm, which less than 5%. This work disclosures a high-quality and large size wave plate of CdSe single crystal, such wave plate has wide application prospects in mid-infrared.

Aeolian sediment transport on Io from lava\u2013frost interactions

Surface modification on Jupiter’s volcanically active moon, Io, has to date been attributed almost exclusively to lava emplacement and volcanic plume deposits. Here we demonstrate that wind-blown transport of sediment may also be altering the Ionian surface. Specifically, shallow subsurface interactions between lava and Io’s widespread sulfur dioxide (SO2) frost can produce localized sublimation vapor flows with sufficient gas densities to enable particle saltation. We calculate anticipated outgassing velocities from lava–SO2 frost interactions, and compare these to the saltation thresholds predicted when accounting for the tenuous nature of the sublimated vapor. We find that saltation may occur if frost temperatures surpass 155 K. Finally we make the first measurements of the dimensions of linear features in images from the Galileo probe, previously termed “ridges”, which demonstrate certain similarities to dunes on other planetary bodies. Io joins a growing list of bodies with tenuous and transient atmospheres where aeolian sediment transport may be an important control on the landscape.

Controlling the Asymmetry of Densified and Porous Hybrid Coatings Based on Vapor Sublimation and Deposition

Controlling the Asymmetry of Densified and Porous Hybrid Coatings Based on Vapor Sublimation and Deposition

Vapor construction and modification of stem cell-laden multicomponent scaffolds for regenerative therapeutics.

Tissue engineering based on the combined use of isolated cells, scaffolds, and growth factors is widely used; however, the manufacture of cell-preloaded scaffolds faces challenges. Herein, we fabricated a multicomponent scaffold with multiple component accommodations, including bioactive molecules (BMs), such as fibroblast growth factor-2 (FGF-2) and l-ascorbic acid 2-phosphate (A2-P), and living cells of human adipose-derived stem cells (hASCs), within one scaffold construct. We report an innovative fabrication process based on vapor-phased construction using iced templates for vapor sublimation. Simultaneously, the vaporized water molecules were replaced by vapor deposition of poly-p-xylylene (PPX, USP Class VI, highly compatible polymer, FDA-approved records), forming a three-dimensional and porous scaffold matrix. More importantly, a multicomponent modification was achieved based on using nonvolatile solutes, including bioactive molecules of FGF-2 and A2-P, and living cells of hASCs, to prepare iced templates for sublimation. Additionally, the fabrication and construction resulted in a multicomponent scaffold product comprising the devised molecules, cells, and vapor-polymerized poly-p-xylylene as the scaffold matrix. The clean and dry fabrication process did not require catalysts, initiators or plasticizers, and potentially harmful solvents, and the scaffold products were produced in simple steps within hours of the processing time. Cell viability analysis showed a high survival rate (approximately 86.4%) for the accommodated hASCs in the fabricated scaffold product, and a surprising multilineage differentiation potential of hASCs was highly upregulated because of synergistic guidance by the same accommodated FGF-2 and A2-P components. Proliferation and self-renewal activities were also demonstrated with enhancement of the multicomponent scaffold product. Finally, in vivo calvarial defect studies further revealed that the constructed scaffolds provided blood vessels to grow into the bone defect areas with enhancement, and the induced conduction of osteoblast growth also promoted bone healing toward osseointegration. The reported scaffold construction technology represents a prospective tissue engineering scaffold product to enable accommodable and customizable versatility to control the distribution and composition of loading delicate BMs and living hASCs in one scaffold construct and demonstrates unlimited applications in tissue engineering repair and regenerative medicine applications.

Thermodynamic Stability of Fenclorim and Clopyralid.

The present work reports an experimental thermodynamic study of two nitrogen heterocyclic organic compounds, fenclorim and clopyralid, that have been used as herbicides. The sublimation vapor pressures of fenclorim (4,6-dichloro-2-phenylpyrimidine) and of clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) were measured, at different temperatures, using a Knudsen mass-loss effusion technique. The vapor pressures of both crystalline and liquid (including supercooled liquid) phases of fenclorim were also determined using a static method based on capacitance diaphragm manometers. The experimental results enabled accurate determination of the standard molar enthalpies, entropies and Gibbs energies of sublimation for both compounds and of vaporization for fenclorim, allowing a phase diagram representation of the (p,T) results, in the neighborhood of the triple point of this compound. The temperatures and molar enthalpies of fusion of the two compounds studied were determined using differential scanning calorimetry. The standard isobaric molar heat capacities of the two crystalline compounds were determined at 298.15 K, using drop calorimetry. The gas phase thermodynamic properties of the two compounds were estimated through ab initio calculations, at the G3(MP2)//B3LYP level, and their thermodynamic stability was evaluated in the gaseous and crystalline phases, considering the calculated values of the standard Gibbs energies of formation, at 298.15 K. All these data, together with other physical and chemical properties, will be useful to predict the mobility and environmental distribution of these two compounds.

Vapor‐Phase Fabrication of Cell‐Accommodated Scaffolds with Multicomponent Functionalization for Neuronal Applications (Adv. Mater. Interfaces 24/2021)

Vapor-Phase Fabrication of Scaffolds A vapor sublimation and deposition process is introduced to construct a multicomponent scaffold composed of pre-load cells and multiple functional molecules, as demonstrated in article number 2100929 by Ting-Ying Wu, Yu-Chih Chiang, Hsien-Yeh Chen, and co-workers. The advanced scaffold system is exploited for a neuronal-guiding differentiation application.

Vapor-phased fabrication and modulation of cell-laden scaffolding materials

Bottom–up approaches using building blocks of modules to fabricate scaffolds for tissue engineering applications have enabled the fabrication of structurally complex and multifunctional materials allowing for physical and chemical flexibility to better mimic the native extracellular matrix. Here we report a vapor-phased fabrication process for constructing three-dimensional modulated scaffold materials via simple steps based on controlling mass transport of vapor sublimation and deposition. We demonstrate the fabrication of scaffolds comprised of multiple biomolecules and living cells with built-in boundaries separating the distinct compartments containing defined biological configurations and functions. We show that the fabricated scaffolds have mass production potential. We demonstrate overall >80% cell viability of encapsulated cells and that modulated scaffolds exhibit enhanced cell proliferation, osteogenesis, and neurogenesis, which can be assembled into various geometric configurations. We perform cell co-culture experiments to show independent osteogenesis and angiogenesis activities from separate compartments in one scaffold construct.

Dielectric and polar properties of aluminum nitride single crystals

The results of the dielectric, pyroelectric, and piezoelectric studies of aluminum nitride single crystals are presented in this paper. The crystals were grown by sublimation and hybrid-chloride vapor phase epitaxy, which provided high growth rates, large sizes, and the ability to reduce structural defects. The pyroelectric effect measurements by a dynamic method using infrared laser radiation (λ = 980 nm) revealed high values of the pyroelectric coefficient up to 30 µC/(m2K). The piezoelectric coefficient d 31 was found about 1.6⋅10−12 m/V.

Vapor Sublimation and Deposition to Fabricate a Porous Methyl Propiolate-Functionalized Poly-p-xylylene Material for Copper-Free Click Chemistry.

Conventional porous materials are mostly synthesized in solution-based methods involving solvents and initiators, and the functionalization of these porous materials usually requires additional and complex steps. In the current study, a methyl propiolate-functionalized porous poly-p-xylylene material was fabricated based on a unique vapor sublimation and deposition process. The process used a water solution and ice as the template with a customizable shape and dimensions, and the conventional chemical vapor deposition (CVD) polymerization of poly-p-xylylene on such an ice template formed a three-dimensional, porous poly-p-xylylene material with interconnected porous structures. More importantly, the functionality of methyl propiolate was well preserved by using methyl propiolate-substituted [2,2]-paracyclophane during the vapor deposition polymerization process and was installed in one step on the final porous poly-p-xylylene products. This functionality exhibited an intact structure and reactivity during the proposed vapor sublimation and deposition process and was proven to have no decomposition or side products after further characterization and conjugation experiments. The electron-withdrawing methyl propiolate group readily provided efficient alkynes as click azide-terminated molecules under copper-free and mild conditions at room temperature and in environmentally friendly solvents, such as water. The resulting methyl propiolate-functionalized porous poly-p-xylylene exhibited interface properties with clickable specific covalent attachment toward azide-terminated target molecules, which are widely available for drugs and biomolecules. The fabricated functional porous materials represent an advanced material featuring porous structures, a straightforward synthetic approach, and precise and controlled interface click chemistry, rendering long-term stability and efficacy to conjugate target functionalities that are expected to attract a variety of new applications.

Vapor-Stripping and Encapsulating to Construct Particles with Time-Controlled Asymmetry and Anisotropy

An innovative chemical vapor sublimation and deposition (CVSD) process was shown to produce nanoscale anisotropic hybrid materials. Taking advantage of controlled thermodynamic properties and the mass transfer of molecules, this process allowed for water vapor sublimation from an iced template/substrate and stagewise vapor deposition of poly-p-xylylene onto the sublimating ice substrate. In this study, the use of sensitive soybean agglutinin (SBA) protein tubes was demonstrated as an example to prepare the anisotropic hybrid material based on the CVSD process. The rationale of a timing parameter, Δt, was controlled to program the sublimation of the SBA-ice templates and the deposition of poly-p-xylylene during the CVSD process. As a result of this control, a stripping stage occurred, during which SBA tubes were exposed on the particle surface, and a subsequent encapsulation stage enabled the transformation of the ice templates into a nanometer-sized anisotropic hybrid material of poly-p-xylylene as the matrix with encapsulated SBA tubes. The timing parameter Δt and the controlled stripping and encapsulating stages during CVSD represent a straightforward and intriguing mechanism stemming from physical chemistry fundamentals for the fabrication of hybrid materials from sensitive molecules and with predetermined sizes and asymmetrical shapes. A simulation analysis showed consistency with the experimental results and controllability of the timing mechanism with predictable particle sizes.

Absolute chemical potentials for complex molecules in fluid phases: A centroid reference for predicting phase equilibria.

Solid-fluid phase equilibria are difficult to predict in simulations because bound degrees of freedom in the crystal phase must be converted to free translations and rotations in the fluid phase. Here, we avoid the solid-to-fluid transformation step by starting with chemical potentials for two reference systems, one for the fluid phase and one for the solid phase. For the solid, we start from the Einstein crystal and transform to the fully interacting molecular crystal. For the fluid phase, we introduce a new reference system, the "centroid," and then transform to gas phase molecules. We illustrate the new calculations by predicting the sublimation vapor pressure of succinic acid in the temperature range of 300 K-350 K.