Polymorphic Transition Research Articles

Impact of cocoa butter and medium chain triglycerides ratios on processing stability, supersaturation, and digestive properties of curcumin-loaded nanostructured lipid carriers

In the pursuit of optimal delivery of hydrophobic agents such as curcumin, the role of lipid composition in the efficacy of nanostructured lipid carriers is gaining significant attention. This study aimed to investigate the effects of cocoa butter (0–10 wt%) and medium chain triglycerides oil (0–10 wt%) mass ratios on processing stability, crystallization, polymorphism transition, supersaturation, encapsulation, and in vitro digestion of curcumin-loaded nanostructured lipid carriers (Cur-NLCs). Transmission electron microscopy (TEM) analysis showed that spherical Cur-NLCs exhibited larger average particle size with the increase in cocoa butter content. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) revealed that the crystallinity and thickness of solid shells decreased with the increase in liquid lipid content. The obtained Cur-NLCs remained stable under various conditions: thermal treatments (25, 37, 60, and 121 °C), varied ionic strengths (50–500 mM), pH changes (2.0–6.0), centrifugation (21382×g for 40 min), and 60-days storage. Furthermore, Cur-NLCs showed higher supersaturation (1863 ± 20–2328 ± 10%) than that of nanoemulsion (1489 ± 6%) and solid lipid nanoparticles (1635 ± 36%). In addition, the prepared Cur-NLCs exhibited high bioaccessibility (79.4 ± 3.1–91.1 ± 2.1%) along with a controlled release of curcumin. This study provides guidelines to prepare Cur-NLCs with tailored physicochemical, functional, and digestion properties to deliver hydrophobic bioactive substances, nutraceuticals, and pharmaceuticals.

In Situ Monitoring of Competitive Coformer Exchange Reaction by 1H MAS Solid-State NMR.

In a competitive coformer exchange reaction, a recent topic of interest in pharmaceutical research, the coformer in a pharmaceutical cocrystal is exchanged with another coformer that is expected to form a cocrystal that is more stable. There will be a competition between coformers to form the most stable product through the formation of hydrogen bonds. This will cause destabilization of the pharmaceutical products during processing or storage. Therefore, it is important to develop a mechanistic understanding of this transformation by monitoring each and every step of the reaction, employing a technique such as 1H nuclear magnetic resonance (NMR). In this study, an in situ monitoring of a coformer exchange reaction is carried out by 1H magic angle spinning (MAS) solid-state NMR (SSNMR) at a spinning frequency of 60 kHz. The changes in caffeine maleic acid cocrystals on addition of glutaric acid and caffeine glutaric cocrystals on addition of maleic acid were monitored. In all of the reactions, it has been observed that caffeine glutaric acid Form I is formed. When glutaric acid was added to 2:1 caffeine maleic acid, the formation of metastable 1:1 caffeine glutaric acid Form I was observed at the start of the experiment, indicating that the centrifugal pressure is enough for the formation. The difference in the end product of the reactions with a similar reaction pathway of 1:1 and 2:1 reactant stoichiometry indicates that a complete replacement of maleic acid has occurred only in the 1:1 stoichiometry of the reactants. The polymorphic transition of caffeine glutaric acid Form II to Form I at higher temperatures was a crucial reason that triggered the exchange of glutaric acid with maleic acid in the reaction of caffeine glutaric acid and maleic acid. Our results are novel since the new reaction pathways in competitive coformer exchange reactions enabled understanding the remarkable role of stoichiometry, polymorphism, temperature, and centrifugal pressure.

Search on stable binary and ternary compounds of two-dimensional transition metal halides

Ab initio driven density functional theory-based high throughput simulations have been conducted to search for stable two-dimensional (2D) structures based on transition metal halides. Binary MeX2 and MeXY (Me—transition element, X and Y–Cr, Br, I, where X ≠ Y) 2D structures in two structural polymorphic modifications, which are 1T-phase and 1H-phase, have been studied. The main structural stability criteria, such as heat formation energy, elasticity constants, and phonon spectra and the following ab initio molecular dynamics simulations have been used to determine the stability of studied compounds. It has been shown that 35 MeX2 and 32 MeXY 2D structures comply with given stability criteria. Photocatalytic properties of these stable 2D MeX2 and 2D MeXY have been investigated. Based on the calculated band gap size E g, work function Ф and electron affinity χ, it has been found that among all stable compounds 13 MeX2 and 16 MeXY 2D structures are promising photocatalysts for water splitting. However, only 7 compounds have solar-to-hydrogen (STH) efficiency overcome the 10% threshold, which is a critical parameter for solar hydrogen generation to be an economically viable resource. Among MeX2 2D structures 1T-CdI2 and 1H-VBr2 possess a STH efficiency of 11.58% and 17.23%. In the case of 2D MeXY, STH efficiencies are 22.79% (1T-ZnClI), 15.20% (1T-CdClI), 22.13% (1T-ZnBrI), 12.11% (1T-CdBrI) and 19.76% (1H-VClBr). Moreover, as a result of this work, a comprehensive publicly available database, containing detailed calculation parameters and fundamental properties of the discovered 2D transition metal halides, has been created.

Synthesis and characterization of complex phosphates of alkaline elements, magnesium and zirconium as potential ceramics for nuclear waste immobilization

Phases of variable composition A2−хА'хMg0.5Zr1.5(PO4)3 (АA' – KNa, KRb, KCs, 0 ≤ x ≤ 2) with langbeinite and kosnarite structures can serve as matrices immobilizing radioactive waste. They were synthesized by sol-gel method followed by heat treatment and investigated by X-ray diffraction at different temperatures, IR spectroscopy, scanning electron microscopy and electron probe microanalysis. A Rietveld refinement of the KCsMg0.5Zr1.5(PO4)3 structure showed that the framework is formed by octahedra (Mg/Zr)O6 and tetrahedra PO4 connected by vertices; potassium and cesium cations are located in cavities. When the temperature changes, phosphates with the langbeinite structure expand uniformly in all directions: αа = αb = αc = (4.2−6.6) ∙ 10−6 °C−1, without undergoing polymorphic transitions. Phosphate Na2Mg0.5Zr1.5(PO4)3, which crystallizes in the kosnarite structure type, expands anisotropically: αа = −2.6·10−6, αс = 8.2·10−6, αav = 1.0·10−6 °C−1. The chemical durability test shows that the leaching rate of Cs ions from the solid solution with langbeinite structure is of the order of 10−5 g cm−2 d−1.

Temperature-induced polymorphic phase transitions in gels and aerogels of nylon 11

Understanding the Brill transition behavior in nylons is particularly important in processing, as the thermal and mechanical properties of these polymers are highly dependent on the structural transitions. In this work, we report the preparation of a thermoreversible gel of nylon 11, which was freeze-dried to obtain the nylon 11 aerogel. Both gel and aerogel samples crystallized predominantly into the γ form at room temperature. The temperature-induced structural transitions of the gel and aerogel samples were studied using wide-angle X-ray diffraction measurements. The gel samples showed a reverse Brill transition from γ to α form on heating and the transition temperature showed a linear dependency on the polymer concentration in gels. On the other hand, the nylon 11 aerogel samples showed a structural transition from γ to high-temperature pseudohexagonal form upon heating. Current results demonstrate that the solvent molecules within the gel samples trigger the chain conformation change from gauche to trans on heating to induce a reverse Brill transition behavior. By adjusting the gel concentration, nylon 11 aerogel samples with varying porosities were obtained, which in turn display low dielectric constant values that rely on density/porosity. Further, the aerogels are also found to be suitable for oil-water separation applications due to their highly hydrophobic nature.

Tensors of thermal deformation for various polymorphic modifications of 2,4-dinitroanisole

The anisotropic characteristics of thermal deformation of ultrapure 2,4-dinitroanisole (2,4-DNAN) crystals were determined by the methods of powder thermorentgenography of the internal standard. The points of structural changes are registered in increments of 10 K, and in the melting region of 2 and 1 K. Calculations of powder X-ray diffraction data are performed by methods of full-profile analysis with a cycle of quantum modeling of the structure of molecules integrated into the algorithm. The Pauli, Le Bail (WPPD), Rietveld (WPPF) and WPPM methods were used as reference methods for full-profile analysis. The main crystallographic axes and characteristic surfaces of the thermal deformation tensor α and β-2,4-DNAN are determined. At atmospheric pressure, the main coefficients of linear (α) and volumetric (β) thermal deformation (expansion) were at 293 K for α-2,4-DNAN with α1(293) = 11,516 × 10−5 K−1, α2(293) = −0,120 × 10−5 K−1, α3(293) = 5,098 × 10−5 K−1, β(293) = 16,333 × 10−5 K−1; at 293 K for β-2,4-DNAN with α1(293) = 13,217 × 10−5 K−1, α2(293) = 0,494 × 10−5 K−1, α3(293) = −8,6504 × 10−5 K−1, β(293) = 6,8191 × 10−5 K−1; at 260 K for β′-2,4-DNAN with α1(260) = 25,214 × 10−5 K−1, α2(260) = −5,823 × 10−5 K−1, α3(260) = 7,741 × 10−5 K−1, β(260) = 27,112 × 10−5 K−1.

Bending the bonds: unveiling halogen interactions in the elastic polymorph of 2,5-bis(3-bromophenyl)furan

This paper investigates the structural properties of 2,5-bis(3-bromophenyl)furan polymorphs, focusing on the halogen interactions and their influence on crystal mechanical properties. In this study, three different polymorphic modifications were obtained which crystallize in the orthorhombic system. Two of the polymorphs possess halogen interactions but only one exhibits elastic properties. Through X-ray diffraction, crystallographic analysis and computational modelling, intricate bromine-based halogen interactions and their impact on the packing arrangement and stability were revealed. The correlation between these interactions and crystal properties, including molecular arrangement and intermolecular forces, is explored. Understanding these relationships is vital for materials design and supramolecular chemistry, enabling the rational synthesis of tailored materials.

Shock-Wave Polymorphic Transition in Porous Graphite

Shock-Wave Polymorphic Transition in Porous Graphite

New polymorphic modification of calcium carbonate — monoclinic aragonite CaCO3

The work discusses the polymorphism of calcium carbonate, the crystal structure of its various polymorphic forms, and the analysis of structure- property correlations. The existence of a novel polymorphic modification of calcium carbonate, monoclinic aragonite CaCO3, has been experimentally discovered. Its crystal structure has been deciphered and its crystal structure has been discussed.

Efavirenz cocrystals with Ascorbic acid: A Strategy for Polymorphic Modification and improvement of Dissolution properties

The objective of this research was to improve the solubility and dissolution rate of Efavirenz (EFA), a BCS II drug utilized for HIV infection treatment, by cocrystallization with ascorbic acid (AA). An in silico analysis indicated that EFA and AA exhibited physical interaction and compatibility. EFA exists in two polymorphic forms, I and II, with varying crystalline habits, where polymorph II presents better solubility and dissolution rate. Cocrystals were prepared using the solvent evaporation method by varying AA concentration and temperature. FTIR and NMR analysis confirmed the absence of chemical interaction between EFA and AA. Increasing AA concentration and temperature significantly increased the saturation solubility. DSC, XRD and SEM analysis revealed a shift in the endothermic peak of EFA, change in intensity with 2θ values, and modified surface morphology respectively. This also confirmed a polymorphic structure change in the cocrystals due to high heating rates and maximum crystallization rate. The dissolution rate of the cocrystals was enhanced by the optimized batch, which contained an intermediate concentration of AA and was subjected to the highest temperature condition, and the data fitted well with the Higuchi model of kinetics. The stability of the cocrystals was also evaluated by accelerated stability testing to determine the percentage of drug content. Thus, cocrystallization with AA proved to be a suitable approach for enhancing the dissolution characteristics and polymorphic modification of BCS II drugs, such as EFA.

Interplay of Polymorphic Transition and Mixed Crystal Formation in Model Fat Systems

Interplay of Polymorphic Transition and Mixed Crystal Formation in Model Fat Systems

N-Alkylimidazol-5-yl-substituted Nitronyl Nitroxides and Their Mononuclear Cu(II) Complexes: Synthesis, Structure and Magnetic Properties.

A novel synthetic approach has been employed to synthesize a series of new nitronyl nitroxides: 2-(1-propyl-1H-imidazol-5-yl)- (Ln-Pr ), 2-(1-isopropyl-1H-imidazol-5-yl)- (Li-Pr ) and 2-(1-butyl-1H-imidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (Ln-Bu ). The reaction of Cu(hfac)2 with LR in a 1 : 2 ratio yields mononuclear heterospin complexes [Cu(hfac)2 (LR )2 ] (LR =Ln-Pr , Li-Pr , Ln-Bu ), which have a similar crystal structure to the "jumping" crystals [Cu(hfac)2 (LMe )2 ] that exhibit chemomechanical activity. It was shown that an increase in the alkyl substituent R leads to changes in the crystal packing of the molecules and the absence of chemomechanical activity. Furthermore, it was found that two polymorph modifications of the heterospin complex [Cu(hfac)2 (Ln-Pr )2 ] can be obtained, and magnetic properties of [Cu(hfac)2 (Ln-Pr )2 ] strongly depend on the angle between the planes of the paramagnetic fragment O•-N-C=N→O and the imidazole ring in Ln-Pr .

Insights into Polymorphic Transition of PVDF during Nonsolvent-Induced Phase Separation

Insights into Polymorphic Transition of PVDF during Nonsolvent-Induced Phase Separation

Numerical Simulation of CdTe Crystal Growth Using the Vertical Gradient Freeze Technique Assisted by Axial Low-Frequency Oscillations of the Melt

The problem of intensification of the melt crystal growth process has been analyzed using CdTe as an actual material. Numerical simulation of 100 mm diameter CdTe crystal growth using the VGF technique has been carried out. The heat–mass transfer was controlled by introducing low-frequency oscillating baffle into the melt, which is a so-called axial vibrational control (AVC) technique. The baffle configuration has been optimized to destroy solid “tails”, which were formed near the crucible walls at high cooling rates due to the low thermoconductivity and the corresponding latent heat. Analysis of CdTe homogeneity range showed that during fast crystal cooling, Te micro precipitations were formed, resulting from the decay of oversaturated Cd-rich nonstoichiometric solid solution during the Bridgman crystal growth technique. After full crystallization, a VGF-grown CdTe crystal stays inside the phase field of the high-temperature wurtzite polymorph. This makes it possible to go through the polymorph transition without Te micro-precipitating using the advantages of the VGF-specific feature of very slow cooling.

The Solid-Phase Transition of Carbapenem CS-023 Polymorphs and the Change in Helicity Observed in the Transition

Anti-solvent crystallization of carbapenem CS-023 was performed at 25 °C. The following results were obtained: (1) A solvate crystal, Form A (5/2 Ethanol·1/2 H2O), was recovered from 80 v/v% ethanol solution; (2) Form A transformed to Form H (4H2O) through solid-phase transition through the solvate-free polymorph, Form A-2, and Form A also transformed into Form C (1Ethanol·3H2O) through solvent-mediated transformation. In the present study, we found that Form C also transforms to Form H through the solid-phase transition through the solvate-free polymorph Form C-2. The three polymorphs, Forms A, H, and C, were composed of helical chain structures. However, there was an incomprehensible affair in the solid-phase transition among the three polymorphs. Namely, Form A comprised a left-handed helix. On the other hand, Form C’s and Form H’s helix chains were in a left- and right-handed helix complex, respectively. The solid-phase transition of Form A into Form H suggested a switch in helicity in the solid. We attempted to explain the helicity change in the solid-phase transition. As a result, we suggest that the over-absorption of water by Form A-2 at high humidity plays a vital role in the helicity change.

Significantly enhanced piezoelectric temperature stability of KNN-based ceramics through multilayer textured thick films composite

The temperature instability of piezoelectric properties in KNN-based ceramics has been a major bottleneck impeding them toward practical applications. Herein, we prepared multilayer composite ceramics using two kinds of textured thick films with different polymorphic phase transition temperatures. The composite ceramics simultaneously exhibited outstanding piezoelectric properties (d33 = 400 ± 20 pC/N; S = 0.18 % at 40 kV/cm) and piezoelectric temperature stability (d33 and S variation within 5 % and 2 %, respectively over the temperature range of room temperature to 180 °C). The synergistic contribution of slightly fluctuating εr·Pr values, the robust phase and domain structures, and the complementary effect of piezoelectric fluctuation between the two composite layers led to the outstanding temperature stability of piezoelectric properties. Furthermore, the piezoelectric energy harvester produced using KNN-T1/T2 composite ceramics exhibits a large power density of 5.4 mW/cm3. These results prove great potential of KNN-T1/T2 ceramics in high temperature piezoelectric devices.

Crystal-to-crystal polymorphic phase transition in a cocrystal accompanied by expansion and surface wettability change

Cocrystal of n-propylparaben and a bipyridine-based azine derivative exhibit heat-induced crystal-to-crystal polymorphic phase transition accompanied by expansion and cracking of the single crystals with distinct wettability properties.

Влияние низкотемпературного отжига неупорядоченных плёнок Ge10Se90 на их оптические свойства

In the present paper, the effect of low-temperature annealing on the linear optical properties of disordered thin films (~350 nm) synthesized from Ge10Se90 glass by vacuum thermal evaporation on quartz substrates is reported. Based on the experimental transmission spectra of films in the field of optical transparency before and after annealing below and at the glass transition temperature Tg = (3612) K (313 and 363 K, respectively), the main optical characteristics (dispersion dependences of the refractive index and extinction coefficient, optical gap energy, the Tautz parameter B1/2, etc.) were determined using the Swanepoel and Tautz methods. It is revealed that the edge of optical absorption in the annealed films is caused by indirect optical transitions. Using the Wemple-DiDomenico single oscillator model, the Urbach energy EU, the energy of one oscillator E0, the scattering energy Ed, the linear susceptibility  and the static refractive index n0 were calculated. At the same time, a higher value of the Ed/E0 ratio of the film annealed at Tg indicates its greater nonlinear susceptibility. The X-ray diffraction studies have confirmed the amorphous nature of the initial films and the appearance of Se nanocrystallites in them after annealing of a certain polymorphic modification depending on the temperature and time of annealing. It was found that annealing both below Tg and at Tg initiates red shift in the optical absorption edge, an increase in EU and , and a decrease in the thickness of the film and the parameter B1/2. It is shown that the annealing of identical films is accompanied by a change in their phase composition with the appearance of either monoclinic beta-Se8 nanocrystallites or the mixture of beta-Se8 and trigonal t-Se. From the standpoint of the concept of the polymerpolymorphoid structure of glass and a glass-forming liquid, it is due to the mutual transformation of polymorphoids of various polymorphic modifications because of a change in their concentration ratio depending on the annealing temperature relative to Tg. The resulting films can be used in optoelectronics as nonlinear optical elements or media for radiation limiters.

Copper- and manganese-based layered hybrid organic–inorganic compounds with polymorphic transitions as energy storage materials

The bis(dodecylammonium) tetrachlorocuprate(ii) and bis(dodecylammonium) tetrachloromanganate(ii) show promise for passively cooling electronics due to their excellent thermal properties, including low thermal hysteresis and good stability.

Oscillatory phase transition induced structural extension during iron oxide reduction

Probing the molecular-level redox behavior and mechanism of oxides is essential to developing innovative applications in different fields such as catalysis, but remains a challenge for the scientific community. Using in-situ transmission electron microscopy, here we provide an overall reduction view of single-crystalline α-Fe2O3 with different characteristics from the conventional wisdom of oxide reduction. Specifically, the formation of epitaxial nanoislands with concomitant oscillatory phase transitions (α-Fe2O3→defective γ-Fe2O3→α-Fe2O3) at the subsurface is observed during reduction. The dynamic equilibrium of lattice oxygen at the surface and the limited oxygen replenishment from the deep layer drive the α-Fe2O3→defective γ-Fe2O3 transformation in the subsurface, while the polymorphic transition (defective γ-Fe2O3→α-Fe2O3) spontaneously occurs under heating conditions. Such oscillatory phase transition is accompanied by the release of asymmetric stress, inducing the extension of epitaxial nanoislands. Our work highlights the complexity of reduction by providing an integral picture of oxide reduction, which contributes to the understanding of the site evolution of oxide-based catalysts in their working state.