Crystallization Conditions Research Articles

Low-temperature laser crystallization of Ge layers grown on MgO substrates

The crystallization of amorphous Ge layers grown at room temperature was investigated using continuous-wave green laser irradiation. The most favorable crystallization conditions for the 40-nm-thick Ge layer were determined by adjusting the laser power density, laser beam shape, and laser scan direction. The optimized laser irradiation crystallizes the amorphous Ge layer in a significantly long-range ordered structure on MgO (001) substrate, whereas that on SiO2/Si substrate becomes polycrystalline. The line-shaped flat-top beam profile of the laser along the MgO [100] scan direction is a decisive factor for uniform crystallization on the MgO substrate. A SiO2 capping layer suppresses heat dissipation from the surface of the amorphous Ge layer and facilitates a lower temperature at the Ge/MgO interface, resulting in the initiation of crystallization from the Ge/MgO interface after laser irradiation. Our analysis indicates that the Ge layer crystallized on MgO (001) substrate exhibits an in-plane epitaxial relationship of Ge [110] // MgO [100] with 45° misorientation.

A snapshot of the transition from monogenetic volcanoes to composite volcanoes: case study on the Wulanhada Volcanic Field (northern China)

Abstract. The transition processes from monogenetic volcanoes to composite volcanoes are poorly understood. The Late Pleistocene to Holocene intraplate monogenetic Wulanhada Volcanic Field (WVF) in northern China provides a snapshot of such a transition. Here we present petrographic observations, mineral chemistry, bulk rock major and trace element data, thermobarometry, and a partial melting model for the WVF to evaluate the lithology and partial melting degree of the mantle source, the crystallization conditions, and pre-eruptive magmatic processes occurring within the magma plumbing system. The far-field effect of India–Eurasia collision resulted in a relatively high degree (10 %–20 %) of partial melting of a carbonate-bearing eclogite (∼ 3 wt % carbonate; Gt/Cpx ≈ 2 : 8, where Gt denotes garnet and Cpx denotes clinopyroxene) followed by interaction with ambient peridotite. The primary melts ascended to the depth of the Moho (∼ 33–36 km depth), crystallized olivine, clinopyroxene and plagioclase at the temperature of 1100–1160 ∘C with the melt water contents of 1.1 wt %–2.3 wt %. Part of the primary melt interacted with the lithospheric mantle during ascent, resulting in an increase in the MgO contents and a decrease in the alkaline contents. The modified magma was subsequently directly emplaced into the middle crust (∼ 23–26 km depth) and crystallized olivine, clinopyroxene and plagioclase at the temperature of 1100–1160 ∘C. The primary melts from the same mantle sources migrated upward to the two-level magma reservoirs to form minerals with complex textures (including reverse and oscillatory zoning and sieve texture). Magma erupted along the NE–SW-striking basement fault and the NW–SE-striking Wulanhada–Gaowusu fault in response to the combined effects of regional tectonic stress and magma replenishment. The crustal magma reservoir in the WVF may represent a snapshot of the transition from monogenetic volcanoes to composite volcanoes. It is possible to form a composite volcano with large magma volumes and complex compositions if the magma is continuously supplied from the source and experiences assimilation and fractional crystallization processes in the magma plumbing system at crustal depth.

Chemistry and Crystallization Conditions of Minerals in Metasomatized Oceanic Lithosphere and Basaltic Rocks of Govorov Guyot, Magellan Seamounts, Pacific Ocean

Studies have provided first detailed data on the chemistry of rock-forming, minor, and accessory minerals of Govorov Guyot volcanic rocks (basalts, trachybasalts, basaltic trachyandesites, and trachyandesites). Some basalt samples bear pargasitic amphibole and clinopyroxene xenocrysts, mantle vein fragments in xenoliths, as well as wehrlite xenoliths, which are remnants of metasomatized oceanic lithosphere. Amphiboles make up a continuous series from pargasite –Mg-hastingsite in wehrlite xenoliths and xenocrysts to Mg-hastingsite–kaersutite end-members in phenocrysts and microlites of basaltic rocks. The discussed issues include the trace element chemistry of Ti-amphibole and clinopyroxene phenocrysts; fractionation of OIB melts; and P-T equilibration of minerals during the formation of mantle and basaltic rocks. Pargasitic amphibole may have crystallized at P-T conditions (2.5–0.6 GPa, 1170–980 °C) corresponding to the spinel facies of peridotite at different depths (73–21 km) in hydrous (6.0–4.5 wt% H2O) silicate mafic melts that percolated through peridotites of the oceanic lithosphere. Ti-amphibole in basaltic rocks crystallized at 1.2–0.4 GPa (40–15 km), and 1060–910 °C from melts containing 8.6–2.6 wt% H2O. As the high-temperature (~1100 °C) basaltic magmas reached chambers at the oceanic crust level (7 to 3 km), the Ti-bearing amphiboles of xenocrysts and phenocrysts became replaced by Ti-magnetite- and/or rhönite-bearing mineral assemblages.

Crystallization Behavior of Poly(ε-Caprolactone)-Hollow Glass Microspheres Composites for Rotational Molding Technology

Composites suitable for rotational molding technology based on poly(ε-caprolactone) (PCL) and filled with hollow glass microspheres (HGM) or functionalized hollow glass microspheres (HGMf) were prepared via melt-compounding. The functionalization of glass microspheres was carried out by a silanization treatment in order to improve the compatibility between the inorganic particles and the polymer matrix and achieve a good dispersion of glass microspheres in the matrix and an enhanced filler–polymer adhesion. The crystallization behavior of materials was studied by DSC under isothermal and non-isothermal conditions and the nucleating effect of the glass microspheres was proven. In particular, the presence of silanized glass microspheres promoted faster crystallization rates and higher nucleation activity, which are enhanced by 75% and 50%, respectively, comparing neat PCL and the composite filled with 20 wt% HGMf. The crystalline and supermolecular structure of PCL and composites crystallized from the melt was evaluated by WAXD and SAXS, highlighting differences in terms of crystallinity index and structural parameters as a function of the adopted crystallization conditions.

Inhibitory role of microRNA-484 in kidney stone formation by repressing calcium oxalate crystallization via a VDR/FoxO1 regulator axis.

Kidney stones are regarded as common malignant diseases in the developed world. As a result, significant research examining their formation is ongoing, with microRNAs (miRs) recently being linked with kidney stone formation. Here, we aim to define the potential role of miR-484 in regulating renal tubular epithelial cell (RTEC) viability and the attachment of calcium oxalate (CaOx) crystals to RTECs via vitamin D receptor (VDR)/forkhead box protein O1 (FoxO1) axis. The pathological condition of CaOx crystallization was induced and examined in Sprague-Dawley rats, while RTECs were isolated and cultured in vitro. Loss- and gain-function assays were performed to study the effects that miR-484, VDR, and FoxO1 on RTEC functions and CaOx crystallization in vitro and on kidney stone formation in vivo. The interaction between miR-484 and VDR was confirmed by dual-luciferase reporter gene assays. Downregulation of miR-484 and FoxO1 as well as overexpression of VDR were identified in kidney stone modelled rats. VDR was confirmed as a target gene of miR-484, while knockdown of VDR upregulated the FoxO1 expression. miR-484 overexpression or VDR suppression reduced RTEC cytotoxicity and crystal attachment to RTECs in vitro and reduced the CaOx crystallization in vivo. Taken together, these findings suggest that miR-484 overexpression may be a potential inhibitor of RTEC proliferation and CaOx crystallization through a VDR/FoxO1 regulatory axis, providing a novel therapeutic target for the treatment of kidney stone.

XENOLITH GARNETS FROM MIR KIMBERLITE PIPE: CHEMICAL COMPOSITION AND EVIDENCE OF METASOMATIC PROCESSES IN THE LITHOSPHERE MANTLE

This paper reports the results on the composition of lithosphere mantle under the Mirny kimberlite field. The authors investigated 57 samples of the mantle xenoliths collected from the Mir pipe. The samples were represented by peridotites (Grt lherzolites) and pyroxenites (Grt websterite, Grt clinopyroxenite and eclogite). The composition of minerals (garnet, clinopyroxene) and various rocks in the lithosphere mantle under the Mirny kimberlite field were analyzed based on petrographic features and chemical data. Besides, PT conditions of rock crystallization were calculated using different geothermobarometers. Garnets from peridotites and websterites show relatively high Mg# (75–83) and low TiO2 contents (up to 0.2 wt. %). Since the eclogite has high-Ca (3.78–9.46 wt. %) and high-Fe (7.77–17.20 wt. %) garnet composition, it lies in the area of wehrlite paragenesis. In general, garnets from the lithosphere mantle under the Mirny kimberlite field have low-Ti garnet composition (up to 0.7 wt. %). Thus, the lithosphere mantle under the Mirny kimberlite field differs from the lithosphere mantle under other diamondiferous fields in a widespread development of eclogite and pyroxenite (up to 50 %), low-Ti composition of rocks, as well as virtual absence of deformed lherzolites. These signs probably indicate minor alteration of silicate metasomatism in the lithospheric mantle under the Mirny field (in contrast to the center of the Siberian craton).

Producing gold nugget simulants using copper alloys

Today the imitations of gold nuggets are highly promising materials in conceptual jewelry design. The manufacturing technology of these materials is based on melted brass casting in a cooling liquid. The purpose of this research is to identify the most favorable technological processes to obtaining high-quality simulants of gold nuggets. The article presents the results of the experimental studies of CW508L brass. The most favorable technological parameters have been identified. They include the melt temperature up to 970±5 °C and use of water with the temperature not higher than 20–25 °C as a cooling liquid. Adherence to the specifications allows to obtain the casts, which superficially resemble natural gold nuggets found in alluvial gold deposits. The casts’ intricate shape and uneven relief providing this resemblance are due to the specific crystallization conditions of brass that differ from the crystallization conditions under conventional casting. The research involved the analysis of the chemical composition of the alloy samples before tests and the samples obtained after casting. After processing the alloy has featured an insignificant decrease in the zinc percentage, and an increase in the impurity content (silica, sulfur, iron, and chrome). The metallographic analysis of the initial sample of CW508L brass has shown a single-phase microstructure that is a solid solution of zinc substitution by copper. The similar study of the casts obtained in the experiment has shown the presence of a β-phase in their structure (along with an α solid solution) that is a CuZn-based solid solution having a positive effect on brass mechanical properties. This microstructure is typical of the alloys undergone accelerated cooling that qualitatively changes the process of melt converting into a solid substance.

Synthesis of zeolite-geopolymer composites with high zeolite content for Pb(II) removal by a simple two-step method using fly ash and metakaolin

Zeolite-geopolymer composites synthesized using industrial solid waste have mechanical strength, high specific surface area and cation exchange ability. This self-supporting adsorbent can replace natural heulandite zeolite to remove metal ions. In this study, a zeolite-geopolymer composite with a high zeolite content was synthesized by a simple two-step process using fly ash and metakaolin as raw materials. The compressive capacity, pore structure and adsorption ability for Pb(II) in the solution of the composite were analyzed and compared with natural heulandite zeolite. Through the two-step synthesis, the dynamic conditions of zeolite crystallization and geopolymer solidification were determined, and the zeolite-geopolymer composite with 57.5% zeolite A content and 6.42 MPa compressive strength was successfully prepared. The composite had hierarchical pore sizes, including microporous, mesoporous and macroporous pores, and its specific surface area was larger than that of natural heulandite zeolite. The Pb(II) adsorption capacity of the composite could reach 446.73 mg/g through ion exchange and hydroxyl reactions in solution, which was higher than the value of 323.37 mg/g for natural heulandite zeolite. Therefore, zeolite-geopolymer composites with high zeolite content synthesized by the simple two-step method can be used as self-supporting adsorbents to replace natural heulandite zeolites for removing metal ions from water.

Isothermal compression of an eclogite from the Western Gneiss Region (Norway)

AbstractIn the Western Gneiss Region in Norway, mafic eclogites form lenses within granitoid orthogneiss and contain the best record of the pressure and temperature evolution of this ultrahigh‐pressure (UHP) terrane. Their exhumation from the UHP conditions has been extensively studied, but their prograde evolution has been rarely quantified although it represents a key constraint for the tectonic history of this area. This study focused on a well‐preserved phengite‐bearing eclogite sample from the Nordfjord region. The sample was investigated using phase‐equilibrium modelling, trace‐element analyses of garnet, trace‐ and major‐element thermobarometry and quartz‐in‐garnet barometry by Raman spectroscopy. Inclusions in garnet core point to crystallization conditions in the amphibolite facies at 510–600°C and 11–16 kbar, whereas chemical zoning in garnet suggests growth during isothermal compression up to the peak pressure of 28 kbar at 600°C, followed by near‐isobaric heating to 660–680°C. Near‐isothermal decompression to 10–14 kbar is recorded in fine‐grained clinopyroxene–amphibole–plagioclase symplectites. The absence of a temperature increase during compression seems incompatible with the classic view of crystallization along a geothermal gradient in a subduction zone and may question the tectonic significance of eclogite facies metamorphism. Two end‐member tectonic scenarios are proposed to explain such an isothermal compression: Either (1) the mafic rocks were originally at depth within the lower crust and were consecutively buried along the isothermal portion of the subducting slab or (2) the mafic rocks recorded up to 14 kbar of tectonic overpressure at constant depth and temperature during the collisional stage of the orogeny.

The Application of N, N -bis(Isonicotinic Acid) 1, 4-Naphthalenedicarboxylic Acid Dihydrazide in Biodegradable Poly(L-lactide): Crystalline Nucleation, Melting Behavior, Thermal Stability and Mechanical Properties

Improving the crystallization performance of poly(L-lactide) (PLLA) is necessary to adapt for various applications. In the current work, N, N -bis(isonicotinic acid) 1, 4-naphthalenedicarboxylic acid dihydrazide (NAIAH) was synthesized to be firstly aimed at promoting the crystallization of PLLA, and the NAIAH-nucleated PLLA materials were prepared using PLLA as a matrix material and NAIAH as a nucleating agent, and the crystalline nucleation, melting behavior, thermal decomposition and mechanical properties of PLLA/NAIAH samples were investigated by the relevant testing instruments. The results from the non-isothermal melt-crystallization from the melt of 190oC indicated that the NAIHA could significantly accelerate PLLA�s crystallization, and played an efficient heterogeneous nucleation in PLLA�s crystallization. The effect of different final melting temperatures on PLLA�s melt-crystallization behavior showed that a relatively low final melting temperature was beneficial for the crystallization of PLLA, and the 170oC was the optimum final melting temperature in this study. An increase of cooling rate could weaken PLLA/NAIAH�s crystallization ability, but the NAIAH was still able to promote PLLA�s crystallization upon the fast cooling at 50oC/min, showing a powerful crystallization accelerating effect of NAIAH. PLLA/NAIAH�s melting behaviors after different crystallization conditions were affected by heating rate and crystallization temperature, and the double melting peaks appeared in melting DSC curves were assigned to melting-recrystallization. Thermal decomposition processes in air showed that the NAIAH decreased PLLA�s thermal stability, but the interaction of PLLA with NAIAH had an inhibition for a drop in onset decomposition temperature. Additionally, the introduction of NAIAH dramatically reduced PLLA�s tensile modulus and elongation at break.

Структуроутворення сталевих виливків у зв’язку з температурно-часовими параметрами плавлення і кристалізації

The paper highlights modern ideas about the features of the processes of crystallization and structure formation in the volume of steel castings, depending on the temperature and time conditions for cooling the melt and cooling the castings, as well as the technological prehistory of charge materials. The analysis of the influence of modification and thermokinetic conditions of crystallization and cooling of steel castings is carried out, taking into account the chemical composition of steels at each stage of the technological cycle for producing cast products. At the stage of selecting charge materials, the conditions for preserving certain metallogenetic features of the initial charge in the structure of steel castings are considered, the existence of an equilibrium temperature (Te), when overheated above which heredity is lost, is considered. Due to this, the possibility of using secondary metal to improve the casting properties without changing their chemical composition is shown. The influence of temperature and time parameters in the pre-crystallization period, namely, the melt overheating temperature, the duration of isothermal treatment and the rate of its subsequent cooling, on the structure formation and properties of steel castings, including taking into account the metallogenetic features of the initial charge, is analyzed. Regularities of the influence of the temperature-time conditions of crystallization in the temperature range of the solid-liquid state on the nature of nucleation and structure formation during the crystallization of steel castings are shown. The features of structure formation and the formation of properties in steel castings under conditions of temperature-kinetic influence after their hardening are determined. And also considered the prospects for obtaining castings with a gradient structure to improve the special properties of cast products. The considered approaches to improve the quality and properties of steel castings open up the prospect of creating new technological solutions and automating technological processes for producing cast products with a predictable set of properties at or above the level of properties of similar rolled products. Keywords: castings, charge, heredity, equilibrium temperature, modification, crystallization, cooling rate, thermal treatment.

Crystallization Conditions for Ingots of High-Strength Aluminum Alloys with an Increased Content of Zirconium

Crystallization Conditions for Ingots of High-Strength Aluminum Alloys with an Increased Content of Zirconium

Polymorphs with Remarkably Distinct Physical and/or Chemical Properties.

Polymorphism in crystals is known since 1822 and the credit goes to Mitscherlich who realized the existence of different crystal structures of the same compound while working with some arsenate and phosphate salts. Later on, this phenomenon was observed also in organic crystals. With the advent of different technologies, especially the easy availability of single crystal XRD instruments, polymorphism in crystals has become a common phenomenon. Almost 37 % of compounds (single component) are polymorphic to date. As the energies of the different polymorphic forms are very close to each other, small changes in crystallization conditions might lead to different polymorphic structures. As a result, sometimes it is difficult to control polymorphism. For this reason, it is considered to be a nuisance to crystal engineering. It has been realized that the property of a material depends not only on the molecular structure but also on its crystal structure. Therefore, it is not only of interest to academia but also has widespread applications in the materials science as well as pharmaceutical industries. In this review, we have discussed polymorphism which causes significant changes in materials properties in different fields of solid-state science, such as electrical, magnetic, SHG, thermal expansion, mechanical, luminescence, color, and pharmaceutical. Therefore, this review will interest researchers from supramolecular chemistry, materials science as well as medicinal chemistry.

3D printing of a composite iPP/quill of chicken feathers functionalized with pimelic acid

AbstractIn this work, the thermomechanical properties of an isotactic polypropylene (iPP)/quill composite were evaluated. This reinforcement was added at 0.5, 1.0 and 5.0 wt% in the iPP matrix. The reinforcement was previously subjected to alkaline treatment with NaOH (QT) and chemical functionalization with pimelic acid (PA) to produce an effective β‐crystal nucleating agent. This functionalization was characterized by Fourier transform infrared spectroscopy (FTIR), showing the presence of a new band at 1571 cm−1 associated with the carboxylate group of pimelic acid, indicating a bond between PA and the quill surface. The internal geometry of the specimens obtained by 3D printing were studied by scanning electron spectroscopy (SEM). The effectiveness of the modified reinforcement as a promoter of the β‐crystalline phase was evaluated by differential scanning calorimetry (DSC) and wide angle X‐ray scattering (WAXD) under non‐isothermal crystallization conditions due to the 3D printing process. The composite that showed a higher index was 1.0% with a value of 64% by DSC and 65% by WAXD. Furthermore, the thermomechanical properties were characterized by dynamic mechanical analysis (DMA) where, for the 0.5% and 1.0% composites, the storage modulus (E') was higher compared to neat iPP. However, for the 5.0% composite the E' values were lower.

Laser ablation combined with Nanoimprint Lithography technology as new surface engineering approach to produce novel polymer-based heteronucleants for recalcitrant protein crystallization

Macromolecule crystallography is currently the most powerful technique for determining the three dimensional structure of proteins at atomic resolution. However, despite its enormous level of technical development achieved, it is still limited by the great difficulty of obtaining crystals that, after exposure to X-rays, allow a high-resolution diffraction pattern from which the structure of the target protein can be elucidated. Even today, the crystallization process is a trial-and-error procedure that requires enormous experimental effort and high economic costs. In this research work, Laser Ablation technology in combination with NanoImprint Lithography was applied on Polycarbonate surfaces to produce novel heteronucleating agents containing multiscale surface topographies (in the micro- and submicro-scale) that promote the growth of protein crystals. Two human proteins, known to be recalcitrant to crystallization when using standard protocols, were used in the assays: (i) a construct of the CNNM4 magnesium transporter lacking amino acid residues 545–730 (HsCNNM4545-730) and (ii) cystathionine beta-synthase enzyme lacking residues 516–525 (HsCBSΔ516-525). The surface engineering solution was validated by comparing the number of novel crystallization conditions induced by those surfaces compared against the control and the use of the Naomi’s Nucleant, a commercially available heteronucleant made of mesoporous bioglass. The aspect ratio of the topography emerges as the topographical parameter that most contributes to protein growth on patterned surfaces. Additionally, the presence of a random distribution of micropores as well as a hierarchical (merging micro- and nano - scale features) surface topography also resulted in a more efficient crystallization process, showing an increment of between 38 and 68% in the number of new crystallization conditions, depending on the surface topography and protein selected. A conclusion is made that Laser Ablation with ultrashort pulses and the combination with Nanoimprint Lithography can be efficiently applied on polymeric substrates to produce a novel concept of heteronucleants that would bridge the gap to the development of universal nucleation agents.

Relating Crystal Structure to Surface Properties: A Study on Quercetin Solid Forms.

The surface energy and surface chemistry of a crystal are of great importance when designing particles for a specific application, as these will impact both downstream manufacturing processes as well as final product quality. In this work, the surface properties of two different quercetin solvates (quercetin dihydrate and quercetin DMSO solvate) were studied using molecular (synthonic) modeling and experimental techniques, including inverse gas chromatography (IGC) and contact angle measurements, to establish a relationship between crystal structure and surface properties. The attachment energy model was used to predict morphologies and calculate surface properties through the study of their growth synthons. The modeling results confirmed the surface chemistry anisotropy for the two forms. For quercetin dihydrate, the {010} facets were found to grow mainly by nonpolar offset quercetin–quercetin stacking interactions, thus being hydrophobic, while the {100} facets were expected to be hydrophilic, growing by a polar quercetin–water hydrogen bond. For QDMSO, the dominant facet {002} grows by a strong polar quercetin–quercetin hydrogen bonding interaction, while the second most dominant facet {011} grows by nonpolar π–π stacking interactions. Water contact angle measurements and IGC confirmed a greater overall surface hydrophilicity for QDMSO compared to QDH and demonstrated surface energy heterogeneity for both structures. This work shows how synthonic modeling can help in the prediction of the surface nature of crystalline particles and guide the choice of parameters that will determine the optimal crystal form and final morphology for targeted surface properties, for example, the choice of crystallization conditions, choice of solvent, or presence of additives or impurities, which can direct the crystallization of a specific crystal form or crystal shape.

Melt-Crystallizations of α and γ Forms of Isotactic Polypropylene in Propene-Butene Copolymers.

Random isotactic propene-butene copolymers (iPPC4) of different stereoregularity have been synthesized with three different homogeneous single center metallocene catalysts having different stereoselectivity. All samples crystallize from the polymerization solution in mixtures of α and γ forms, and the relative amount of γ form increases with increasing concentrations of butene and of rr stereodefects. All samples crystallize from the melt in mixtures of α and γ forms and the fraction of γ form increases with decreasing cooling rate. At high cooling rates, the crystallization of the α form is always favored, even for samples that contain high total concentration of defects that should crystallize in the γ form. The results demonstrate that in iPPs containing significant concentrations of defects, such as stereodefects and comonomeric units, the γ form is the thermodynamically stable form of iPP and crystallizes in selective conditions of very slow crystallization, whereas the α form is the kinetically favored form and crystallizes in conditions of fast crystallization.

Exploration of process optimization for recovery of sodium and ammonium sulfate crystals from vanadium precipitation wastewater

In this paper, we have studied vanadium precipitation wastewater in two stages of the fractional crystallization process. In order to extract sodium sulfate and ammonium sulfate products with large particle size and uniform particle size distribution from the rear end vanadium precipitation wastewater and to realize the resource reuse of vanadium precipitation wastewater, the effects of various operating parameters (seeding amount, evaporation rate, stirring rate, growing time) on the particle size and particle size distribution of sodium sulfate and ammonium sulfate products were investigated. Better separation and crystallization conditions of sodium sulfate and ammonium sulfate were obtained. The optimized crystallization conditions of sodium sulfate are: the addition amount of ammonium sulfate seeding with a particle size of 40 μm is 1.17 %, the evaporation rate is 100 mL/h, the stirring rate is 80 rpm, the crystal growth time is 60 min, and the main particle size M.S. value of sodium sulfate crystals is 242.23 μm; The optimized crystallization conditions of ammonium sulfate were as follows: the addition amount of sodium sulfate seeding with a particle size of 80 μm was 0.68 %, the evaporation rate was 160 mL/h, the stirring rate was 150 rpm, and the crystal growth time was 30 min. The M.S. value of the final ammonium sulfate crystal was 880 μm.

Effect of Homologation on the Polymorphism of Anthranilic Acids

A series of homologues (1–4) of fenamic acid have been synthesized by varying the length of the linker between the two aromatic rings, and their polymorphism has been investigated. Under the same crystallization conditions, each of the newly synthesized compounds leads to two forms, except for compound 1, which indicates that additional flexibility due to homologation does not necessarily lead to more polymorphs. The molecules in each polymorphic system show different conformations due to the rotation about specific sigma bonds. Phase transitions are observed between the polymorphs of each system. Conformational analysis and Hirshfeld surface analysis were applied to investigate the effect of conformational flexibility on the polymorphism of these compounds.

Precise Control of Two-Dimensional Platelet Micelles from Biodegradable Poly(p-dioxanone) Block Copolymers by Crystallization-Driven Self-Assembly

Two-dimensional (2D) core–shell nanoparticles have been attracting increasing interest due to their wide applications in materials science. Living crystallization-driven self-assembly (CDSA) is an ambient temperature, seeded growth method of crystallizable block copolymers (BCPs) in selective solvents, which has been demonstrated to be a powerful tool for the creation of one-dimensional (1D)/2D nanomaterials with precise control over size and compositions. Nevertheless, the development of an efficient living CDSA approach is a challenge for the case of semicrystalline poly(p-dioxanone) (PPDO) as a core-forming block, where the dimensional control is poor. Herein, we demonstrate that the insufficient size control of 2D PPDO platelets could be overcome through modulation of solvent compositions or elevating the crystallization temperatures for PPDO. The possible mechanism involves an improved unimer solubility that avoids fast unimer aggregation. As a result, uniform 2D platelet micelles with a controlled area over a substantial size range are created via epitaxial growth of the unimer. It is noteworthy that the shape control of 2D platelet micelles from quasi-square to elongated hexagon to lozenge shapes can be accessible by regulating the crystallization conditions such as adding different amounts of cosolvents or crystallization at an elevated temperature. Meanwhile, spatially defined block comicelles can be achieved via the seeded growth approach from PPDO core-forming BCPs with different corona functionalities at elevated temperatures. The excellent water stability and biocompatibility properties of 2D PPDO platelet micelles further enable them to have a potential application as cargo vehicles in the drug delivery field.