Vesicle systems for mimicking the effects of 2,4-dichlorophenol on cell membranes

The effect of 2,4-dichlorophenol (DCP) on the phosphatidylethanolamine ( --dipalmitoyl-phosphatidylethanolamine (DPPE))/water liposomes was studied in the temperature domains of the gel and liquid crystalline phases at the DCP/DPPE molar ratios of 10⁻¹ and 10⁻³ by using differential scanning calorimetry (DSC) as well as small and wide angle X-ray scattering (SAXS and WAXS). Different character of the transitions between the gel and the liquid crystalline phases was observed in the lipid/water and by DCP-doped systems. The different DCP concentrations caused similar effects in the change of the layer arrangements of the gel phase, while the perturbation of the subcells of this phase was different. In the liquid crystalline phase, the DCP molecules did not affect the layer structure significantly. The calorimetrical behaviour of the systems were rather correlated to the changes of the subcells than to the layer arrangements.     

Crystalline degradation products of vancomycin as chiral stationary phase in microcolumn liquid chromatography

The ability of crystalline degradation products (CDPs) of vancomycin as a chiral stationary phase was reported in a previous study for enantioselective separation of drugs, amino acids and agrochemical toxins by conventional LC column (250 x 4.6 mm). In this work, the potential of CDP of vancomycin for the enantiomeric separation in micro-LC (200 x 1 mm) has been studied. The obtained separation results are better than in our previous study with conventional LC columns. The enantiomers of D,L-phenylalanine, D,L-alanine, methyldopa, atropine and propranolol were used for this evaluation. Experiments have been carried out in a stainless steel tube that was packed with chiral silica particles of 3 and 12 microm diameters. Also, three different ratios of 3 and 12 microm silica particles were used for packing material of chiral columns and the effect on aspect ratio and resolving powers was compared.     

Microporous membranes obtained from polypropylene blend films by stretching

Blends of two linear polypropylenes (PP, having different molecular weights) were prepared to develop microporous membranes through melt extrusion followed by stretching. The role of high molecular weight chains on the row-nucleated lamellar crystallization was investigated. The orientation of crystalline and amorphous phases was measured by wide angle X-ray diffraction (WAXD) and Fourier transform infrared (FTIR). Long period spacing was obtained using small angle X-ray scattering (SAXS). The effects of annealing temperature and applied elongation during annealing on the crystallinity of the films were studied using differential scanning calorimetry (DSC). It was found that annealing at 140 °C contributed significantly to the perfection of the crystalline phase. Scanning electron microscopy (SEM) images of the membrane surface showed more pore density and uniform pore size as the amount of high molecular weight component increased. The addition of the high M_w PP improved the water vapor transmission rate (WVTR) of the membranes, indicating increased interconnectivity of the pores, which was also confirmed from cross-section SEM micrographs of the membranes. The surface area and pore dimensions of the microporous membranes were measured using the BET nitrogen absorption technique and mercury porosimetry, respectively. The influences of temperature and amount of stretching during cold and hot stretching on WVTR were also explored. Tensile properties in the machine and transverse directions (MD and TD, respectively) as well as puncture resistance in the normal direction (ND) were evaluated. As the high M_w PP was added, a slight reduction in the mechanical properties along MD and TD and no changes in ND were observed.     

Stochastic evolution of 2D crystals

We study a crystalline version of the modified Stefan problem in the plane. The feature of our approach is that, we consider a model with stochastic perturbations and assume the interfacial curve to be a polygon. The existence of solution to our stochastic system is established. Galerkin’s method is one of the main tools used in the proof of our assertion.     

The Crystalline State of Macromolecular Substances

Unlike low molecular weight substances, high polymers do not crystallize completely. However long the crystallization process is continued, they still consist of a mixture of crystalline and non crystalline regions. In the undrawn material, these regions form larger units which are known as spherulites. Questions that are of special interest concern the arrangement of the chains in the noncrystalline regions, the causes of chain folding, and the imperfections in the crystals. The incomplete crystallization is a consequence of kinetic inhibitions. This can be deduced from the fact that the crystalline fraction increases with rising crystallization temperature. If polymerization is carried out in the solid crystalline state, one obtains a completely crystalline polymeric material.     

Polyurethane/montmorillonite nanocomposites prepared from crystalline polyols, using 1,4-butanediol and organoclay hybrid as chain extenders

Polyurethane/montmorillonite (PU/MMT) nanocomposites were prepared via in situ polymerization from highly crystalline poly(butylene succinate)/poly(ethylene glycol) polyols and 4,4^′-dicyclohexylmethane diisocyanate, using both 1,4-butanediol and 1, 2, or 3 wt.% of a tris(hydroxymethyl)aminomethane-MMT hybrid, as chain extenders. The corresponding nanocomposites were designated PU-1MMT, PU-2MMT and PU-3MMT, respectively. The layered silicates were mostly intercalated in the nanocomposites. The distances between the individual silicate layers in the PU-1MMT and PU-2MMT were in the range of 2-10 nm, while those in the PU-3MMT were only about 2 nm. The inefficient exfoliation of the clay in this system was mainly due to the high crystallinity and polarity of the PBS polyol. There were no significant changes in the thermal properties of the pure PU and PU nanocomposites. However, the tensile modulus and elongation of the PU-2MMT at break were significantly greater than those of the pure PU and PU-3MMT.     

Influence of heating rate on the crystalline properties of 0.7BiFeO3-0.3PbTiO3 thin films prepared by sol-gel process

0.7BiFeO₃-0.3PbTiO₃ (BFPT7030) thin films were deposited on SiO₂/Si substrates by sol-gel process. The influence of heating rate on the crystalline properties of BFPT7030 thin films were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). XRD patterns of the films showed that a pure perovskite phase exists in BFPT7030 films annealed by rapid thermal annealing (RTA) technique. SEM and AFM observations demonstrated that the BFPT7030 films annealed by RTA at 700 °C for 90 s with the heating rate of 1 °C s⁻¹ could show a dense, crack-free surface morphology, and the films’ grains grow better than those of the films annealed by RTA at the same temperature with other heating rates. XPS results of the films indicated that the ratio of Fe³⁺:Fe²⁺ is about 21:10 and 9:5 for the films annealed by RTA at 700 °C for 90 s with the heating rate of 1 and 20 °C s⁻¹, respectively. That means the higher the heating rate, the higher the concentration of Fe²⁺ in the BFPT7030 thin films.     

Covalent Organic Frameworks for Extracting Water from Air

Water scarcity is becoming an increasingly pressing issue due to global population growth and industrialization. One effective approach to addressing this issue is sorption-based atmospheric water harvesting (SAWH). Covalent organic frameworks (COFs) are a type of porous crystalline material that have emerged as promising sorbents for water harvesting due to their high surface area, tunable pore size, and customizable pore chemistry. In this mini-review, we provide an overview of the different types of COFs, their structural characteristics, and the diverse linkage chemistries used to construct them. Then, we summarize recent advances in using COF-based sorbents for atmospheric water harvesting, including strategies for controlling sorption properties and optimizing performance in terms of thermodynamics and dynamics. Finally, we discuss prospects and challenges associated with improving the efficiency of COF-based SAWH systems.     

Chirality manipulation of supramolecular self-assembly based on the host-guest chemistry of cyclodextrin

Chiral materials have been of the interests of scientists for nearly a century. People have endeavored a great effort to manipulate the chirality of various self-assembled materials. Among these efforts, cyclodextrins are used only in recent years, although it has long been recognized that the chirality of cyclodextrin can be transferred to the guest. In this review, we for the first time summarize the recent advancement of the supramolecular chirality manipulation on the basis of the host-guest chemistry of cyclodextrins. By using the simple Harata-Kodaka's rule, natural cyclodextrins can be exploited in a dynamic manner to create chirality inversion materials through crystalline self-assembly, which is facile and environment-friendly. What is more, we also discussed the remarks on future outlooks at the end of this article and expect it to stimulate a rapid development on both the theory and application level.     

Novel Stereocontrolled Preparation of Amino Polyols from 2,3-Aziridine Alcohols

Starting from 2,3-aziridine alcohols, a novel and versatile preparation of optically active amino polyol was achieved using a simple strategy with few purification steps and a good overall yield.