The crystal layer growth rate is governed by the heat transfer in a layer melt crystallization process and is essential to the separation efficiency. Herein, a numerical model was proposed to predict the solid−liquid (S-L) interface temperature and the growth rate of the crystal layer. The heat transfer equation was taken as the governing equation, combining crystal layer growth kinetics, mass balance, and heat balance in the model which were solved using the finite volume method. The calculation results provided details of temperature distribution in the crystal layer, temperature of the moving S-L interface, and the layer growth rate. The simulated results were validated by experiments using P-xylene as the model substance. Finally, the crystal layer growth rate was found to be very sensitive to the seeding supercooling, especially at the early stage right after seeding. The proper seeding supercooling could be optimized by this model according to both the optimized crystal layer growth rate and productivity.
In order to improve the aqueous solubility of clotrimazole (CLT), an effective antifungal agent, its new multicomponent crystals were developed according to crystal engineering. To efficiently synthesize the multicomponent solids,...
Cocrystal
engineering is gaining interest across various disciplines
since it can effectively tune the properties of solid substances via
noncovalent synthesis by introducing new components into the lattice.
Mechanochemistry is without a doubt the most valuable tool for the
research of cocrystals, which combines the pursuit of efficient and
sustainable process pathways with the exploration of supramolecular
synthons that cannot be discovered using solution methods. In this
review, concerning the significance of the mechanochemical synthesis
of cocrystals, we begin by outlining the strategies for mechanochemical
preparation of cocrystals. We then elaborate on the theoretical mechanisms
of the mechanochemically induced formation of cocrystals and their
polymorphs. On this foundation, several cross-fields in which mechanochemistry
enhances the application value of cocrystal engineering are shown
to overcome existing limitations, which are difficult or impossible
to access using conventional solution methods. More importantly, we
demonstrate that the introduction of new methods, such as cultivating
single crystals from melt microdroplets, and new techniques, such
as microelectron diffraction (Micro-ED), has harmoniously united the
fields of cocrystal engineering and mechanochemistry. Finally, a brief
conclusion and outlook are presented, including current challenges
and future opportunities for the cooperation of mechanochemistry and
cocrystal engineering.
Flexible fluorescent crystalline materials exhibit both
mechanical
and optical properties and have received great attention due to their
potential applications in flexible optical devices. Simultaneously
adjusting the mechanical and optical properties of crystalline materials
remains interesting and challenging. In the present work, a guest
molecule was introduced via hydrogen-bonded solvation, which achieved
excellent mechanical elasticity and higher fluorescence emission than
that of the host heterocyclic Schiff base molecule crystal itself.
The crystal structure–property relationship and the molecular
mechanism of the elasticity were then investigated in detail. It revealed
that solvent molecules play a key role in changing both the stacking
of fluorescent molecules and the interaction energy framework. In
addition, the flexible fluorescent solvate exhibits a good waveguide
property. A bent crystal was found to have a larger optical loss coefficient
than a straight crystal. Furthermore, the size effect on the optical
loss coefficient of the waveguide was discussed in which the optical
loss coefficient decreases as the sizes increase. Such a size effect
is usually neglected in waveguide material research and should be
complemented in the performance evaluation of optical waveguides.
Tautomers are structural isomers that readily interconvert and may exhibit different properties. The effect of solvent on tautomeric equilibria in solution has been a subject of some research. Tautomer solvate is less common, and the role of solvent in the crystallization of tautomer solvate remains an interesting topic. In this work, we used 6-amino-1,3-dimethyl-5-nitrosouracil (NAU) as the tautomeric model material, which can present in nitrone-enamine form (Tautomer A) or oxime-imine form (Tautomer B). A solvate with NAU/DMSO ratio of 1:1 was discovered and characterized using single/ powder X-ray diffraction and thermogravimetry. The crystal structure of NAU•DMSO was determined for the first time, where only Tautomer A was formed in the tautomeric crystal. Quantum chemical calculation and molecular dynamics simulation were conducted to determine the tautomeric form in DMSO solution. Electrostatic potential analysis, radial distribution function analysis, and binding energy suggested possible DMSO-NAU interaction modes and stable tautomer complexes in solution. Tautomer A-containing complexes were found to dominate in solution, as verified by comparing predicted and experimental 1 H NMR spectra. Findings reveal that the hydrogen bonding between DMSO and NAU is similar in solution and in NAU-DMSO solvate crystal, which helps preserve the form of Tautomer A during solvate crystallization.
The solubility of PMN in 13 organic solvents (methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, acetone, acetonitrile, methyl acetate, ethyl acetate, n-propyl acetate, and isopropyl acetate) was determined by the gravimetric method over the temperatures ranging from 278.15 to 318.15 K at 0.1 MPa. The solubility of all selected solvents increases with increasing temperature; however, the change in methanol is substantially more than that in other solvents. Four models, including the modified Apelblat equation, the λh equation, the NRTL, and the van't Hoff equation, were applied to correlate the experimental solubility data, which showed that a relative deviation is less than 3% with the four models. In addition, a KAT-LSER model was employed to quantitatively evaluate and describe the solvent effect, which indicate that the hydrogen bonding basicity of solvents has a greater effect on the solubility of PMN.
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