Topology of ferroelectric nematic droplets: the case driven by flexoelectricity or depolarization field.

The recent discovery of ferroelectric nematics provides new opportunities for exploring polar topology in liquid matter. Here, we report numerous potential polarization topological states (e.g., polar vortex-like and line disclination mediated structures) in confined ferroelectric nematics with similar free-energy levels. In the experiment, they appear according to the confinement size and surface anchoring conditions. Based on a minimal analytical approach, we reveal that the topological transformation is balanced among the nematic elasticity, the polarization gradient, the flexoelectric and the depolarization interactions.

How Far Can We Push the Rigid Oligomers/Polymers toward Ferroelectric Nematic Liquid Crystals?

The emerging ferroelectric nematic (NF) liquid crystal is a novel 3D-ordered liquid exhibiting macroscopic electric polarization. The combination of the ultrahigh dielectric constant, strong nonlinear optical signal, and high sensitivity to the electric field makes NF materials promising for the development of advanced liquid crystal electroopic devices. Previously, all studies focused on the rod-shaped small molecules with limited length (l) range and dipole moment (µ) values. Here, through the precision synthesis, we extend the aromatic rod-shaped mesogen to oligomer/polymer (repeat unit up to 12 with monodisperse molecular-weight dispersion) and increase the µ value over 30 Debye (D). The NF phase has a widespread existence far beyond our expectation and could be observed in all the oligomer/polymer length range. Notably, the NF phase experiences a nontrivial evolution pathway with the traditional apolar nematic phase completely suppressed, i.e., the NF phase nucleates directly from the isotropic liquid phase. The discovery of thte ferroelectric packing of oligomer/polymer rods not only offers the concept of extending the NF state to oligomers/polymers but also provides some previously overlooked insights in oxybenzoate-based liquid crystal polymer materials.

Divergent Syntheses of Isoquinolines and Indolo[1,2-a]quinazolines by Copper-Catalyzed Cascade Annulation from 2-Haloaryloxime Acetates with Active Methylene Compounds and Indoles.

A convenient and reliable method for the direct construction of isoquinolines is described. A series of isoquinoline derivatives were synthesized, with high chemo- and regioselectivities, via the copper-catalyzed cascade reaction of 2-haloaryloxime acetates with ß-diketones, ß-keto esters, and ß-keto nitriles. This tandem annulation process features inexpensive catalysts, no need for additional ligands, and excellent functional group tolerance, which makes it have potential synthetic applications. Furthermore, this strategy could also be used to enter functionalized indolo[1,2-a]quinazolines by using indoles as the counterpart of the 2-haloaryloxime acetates.

Access to Thiazole via Copper-Catalyzed [3+1+1]-Type Condensation Reaction under Redox-Neutral Conditions.

A new strategy for thiazoles via copper-catalyzed [3+1+1]-type condensation reaction from oximes, anhydrides and potassiumthiocyanate (KSCN) is developed herein. The transformation has good functional group tolerance and various thiazoles were formed smoothly in good to excellent yields under mild reaction conditions. This process involves copper-catalyzed N-O/C-S bond cleavages, activation of vinyl sp2 C-H bond, and C-S/C-N bond formations which are under redox-neutral conditions as well as operational simplicity.

Cu-Catalyzed Three-Component Cascade Annulation Reaction: An Entry to Functionalized Pyridines.

A concise copper-catalyzed N-O bond cleavage/C-C/C-N bond formation procedure has been described for the synthesis of multisubstituted pyridines. Various oxime acetates, activated methylene compounds, and a wide range of aldehydes bearing aryl, heteroaryl, vinyl, and trifluoromethyl groups were employed to provide the tri- or tetrasubstituted pyridines with flexible substitution patterns. Moreover, this method features inexpensive catalysts, no need for extra oxidant, and high step-enconomy, which make it pratical and attractive.

Copper-catalyzed coupling of oxime acetates with sodium sulfinates: an efficient synthesis of sulfone derivatives.

Sulfone derivatives are important synthetic intermediates. However, the general method for their preparation is through traditional coupling reaction: the alkylation of sodium sulfinates with phenacyl halides. Based on our previous work on sodium sulfinates and oxime acetates, we herein report a novel method for sulfone derivatives by oxidative coupling with sodium sulfinates and oxime acetates using copper as catalyst. The sulfonylvinylamine products could be formed in excellent yields. Upon hydrolysis by silica gel in CH2 Cl2 , ß-ketosulfones could also be efficiently constructed. Various sulfonylvinylamines and ß-ketosulfones were obtained in good to excellent yields under the optimized reaction conditions. Mechanistic studies indicated that this transformation involved copper-catalyzed N-O bond cleavage, activation of a vinyl sp(2) C-H bond, and C-S bond formation. The oxime acetates act as both a substrate and an oxidant, thus the reaction needs no additional oxidants or additives.

High ambient temperature increases the number of emergency visits for upper urolithiasis in Hefei City, China.

Background: Few studies have examined the effect of ambient temperature on upper urolithiasis in developing countries, with even fewer considering individual factors. Methods: The present study analyzed data on emergency department visits for upper urolithiasis from three hospital sites of a large hospital in Hefei, China, during 2016-2020. Data on environmental factors during the same period were also analyzed. A time series analysis employing a generalized Poisson regression model (GPRM) combined with a distributed lag non-linear model (DLNM) was conducted to evaluate the effect of ambient temperature on the number of emergency department visits for upper urolithiasis. Results: We found that ambient temperatures above 9 °C were positively associated with the frequency of upper urolithiasis visits, with the relationship being most significant on the current day and with a one-day lag. In the single-day lag effect, the most significant relative risk (RR) for mild heat (75th percentile) and high heat (95th percentile) was 1.229 (95% CI: 1.100-1.373) and 1.337 (95% CI: 1.134-1.577), respectively. The cumulative lag effect was significantly higher than the single-day lag effect, with maximum relative risks (RRs) of 1.779 (95% CI: 1.356-2.335) and 2.498 (95% CI: 1.688-3.697), respectively. The maximum lag time was 7 days. RRs were also higher among women and individuals aged 30-44 years. Conclusions: Increased ambient temperature is a risk factor for upper urolithiasis, and there is a hysteresis effect. Women and individuals aged 30-44 years are the most susceptible.

Spontaneous electric-polarization topology in confined ferroelectric nematics.

Topological textures have fascinated people in different areas of physics and technologies. However, the observations are limited in magnetic and solid-state ferroelectric systems. Ferroelectric nematic is the first liquid-state ferroelectric that would carry many possibilities of spatially-distributed polarization fields. Contrary to traditional magnetic or crystalline systems, anisotropic liquid crystal interactions can compete with the polarization counterparts, thereby setting a challenge in understating their interplays and the resultant topologies. Here, we discover chiral polarization meron-like structures, which appear during the emergence and growth of quasi-2D ferroelectric nematic domains. The chirality can emerge spontaneously in polar textures and can be additionally biased by introducing chiral dopants. Such micrometre-scale polarization textures are the modified electric variants of the magnetic merons. Both experimental and an extended mean-field modelling reveal that the polarization strength plays a dedicated role in determining polarization topology, providing a guide for exploring diverse polar textures in strongly-polarized liquid crystals.

Practical synthesis of pyrazoles via a copper-catalyzed relay oxidation strategy.

Various 1,3- and 1,3,4-substituted pyrazoles are smoothly formed via copper-catalyzed cascade reactions of oxime acetates, amines and aldehydes. This relay oxidative process involves copper-promoted N-O bond cleavage and C-C/C-N/N-N bond formations to furnish pyrazolines, and sequential Cu-O2 system-involved oxidative dehydrogenation of pyrazolines to afford pyrazoles. This transformation provides a novel and versatile approach for the synthesis of pyrazoles, with an inexpensive copper catalyst and green oxidants. It is atom- and step-economical, and possesses a good functional group tolerance, as well as operational simplicity.