Polar Organic Solvents Research Articles

A novel merocyanine photoacid for visible light-controlled pH modulation

Merocyanine-based photoacids generate high proton concentrations under visible light irradiation. In the past decade, it has been established that these photoacids offer significant advantages over photoacid generators (PAGs) and hydroxyaryl photoacids, enabling better spatiotemporal control of proton transfer reactions in bulk media. In this study, we modified the core structure of the first generation of meroyanine photoacids. We developed a novel photoacid with color tuning capabilities and high solubility in polar organic solvents. Specifically, by incorporating a cationic benzoindolium moiety as an acceptor, we have altered the photoacid’s light absorption properties. Unlike the first generation of indolium-based merocyanine photoacids, this photoacid can now be activated with green light (λmax = 525 nm) as well as blue (λmax = 450 nm) and ultraviolet (λmax = 365 nm) lights. Furthermore, the novel photoacid exhibits high photo stability, photo-acidity (Π = 3.28 ± 0.08) and moderate reverse reaction rate (k = 1.08 × 10−3 ± 0.00017 s−1) in solution. We envision that with improved color tuning capabilities, this class of photoacids will be a more versatile tool for controlling proton-induced reactions in different systems, including biological reactions.

Novel Bis(4-aminophenoxy) Benzene-Based Aramid Copolymers with Enhanced Solution Processability.

Aramid copolymers have garnered significant interest due to their potential applications in extreme environments such as the aerospace, defense, and automotive industries. Recent developments in aramid copolymers have moved beyond their traditional use in high-strength, high-temperature resistant fibers. There is now a demand for new polymers that can easily be processed into thin films for applications such as electrical insulation films and membranes, utilizing the inherent properties of aramid copolymers. In this work, we demonstrate two novel aramid copolymers that are capable of polymerizing in polar organic solvents with a high degree of polymerization, achieved by incorporating flexible bis(4-aminophenoxy) benzene moieties into the chain backbone. The synthesized MBAB-aramid and PBAB-aramid have enabled the fabrication of exceptionally thin, clear films, with an average molecular weight exceeding 150 kDa and a thickness ranging from 3 to 10 μm. The dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) reveal that the thin films of MBAB-aramid and PBAB-aramid exhibited glass transition temperatures of 270.1 °C and 292.7 °C, respectively, and thermal decomposition temperatures of 449.6 °C and 465.5 °C, respectively. The mechanical tensile analysis of the 5 μm thick films confirmed that the tensile strengths, with elongation at break, are 107.1 MPa (50.7%) for MBAB-aramid and 113.5 MPa (58.4%) for PBAB-aramid, respectively. The thermal and mechanical properties consistently differ between the two polymers, which is attributed to variations in the linearity of the polymer structures and the resulting differences in the density of intermolecular hydrogen bonding and pi-pi interactions. The resulting high-strength, ultra-thin aramid materials offer numerous potential applications in thin films, membranes, and functional coatings across various industries.

TFE Terpolymers: Once Promising - Are There Still Perspectives in the 21st Century? Part II: Processing, Properties, Applications.

Tetrafluoroethylene (TFE) terpolymers have emerged as advantageous substitutes for polytetrafluoroethylene (PTFE). Therefore, they are being considered as alternatives to PTFE in many application areas. The advantages of TFE terpolymers include their facile processability at elevated temperatures, their solubility in some polar organic solvents, their inertness against aqueous acids, aqueous bases and a large number of mostly nonpolar organic solvents, their low dielectric constant, their low refractive index as well as useful electro- and thermochemical properties. This review on TFE terpolymers focuses on their processing including shaping and surface modification as well as on selected properties including wettability, dielectric properties, mechanical response behavior, chemical stability, and degradability. Applications including their use as elastomeric sealing material, liner and cladding layer as well as their use as material for membranes, microfluidic devices, photonics, photovoltaics, energy storage, energy harvesting, sensors, and nanothermitic composites will be discussed. The review concludes with a discussion of the future potential of TFE terpolymers and scientific challenges to be addressed by future research on TFE terpolymers.

X-ray structures, thermal stabilities and kinetics of guest desolvation of complexes of three fluorenone-derived host compounds with the polar aprotic guest solvent, tetramethylurea

Abstract The wheel-and-axle host compounds 9,9′-(1,4-phenylene)bis(fluoren-9-ol) (H1), 9,9′-(ethyne-1,2-diyl)bis(fluoren-9-ol) (H2) and 9,9′-(biphenyl-4,4′-diyl)bis(fluoren-9-ol) (H3) each formed complexes with tetramethylurea (TMU), a polar aprotic organic solvent, with host: guest ratios of 1:2. Single crystal X-ray diffraction revealed that these complexes crystallized in the monoclinic space group P21/c, their analyses being performed in P21/c for H1⋅2(TMU) and in the alternative setting P21/n for both H2·2(TMU) and H3·2(TMU). Furthermore, these inclusion compounds are stabilized by both classical and non-classical hydrogen bonds between the host and guest molecules. Hirshfeld surface analyses demonstrated that the percentage of interatomic (host)H···O(guest) interactions ranged between 7.8 and 10.3%, while thermal analyses showed that the relative thermal stabilities of these complexes were high, with the onset temperatures for the guest release event, Ton, being 83.1 (H1·2(TMU)), 81.1 (H2·2(TMU)) and 90.3 °C (H3·2(TMU)). Moreover, the calculated mass loss percentages, after heating each complex in a controlled manner to release the guest species, correlated closely with those expected for these 1:2 host: guest inclusion complexes. Finally, determination of the activation energies for complex desolvation yielded 148.7 ± 5.4, 128.6 ± 10.8 and 149.4 ± 0.8 kJ·mol‒1 for H1·2(TMU), H2·2(TMU) and H3·2(TMU) respectively. A single guest desolvation mechanism was at work in the first and last of these complexes, while this mechanism in H2·2(TMU) changed during this process. The H1·2(TMU) inclusion complex has been reported previously, and the results obtained in that work are also compared with those from the present investigation.

Eco-friendly hydrotropic spectrophotometric analysis of ranolazine hydrochloride

Simple and eco-friendly biodegradable hydrotropes-assisted spectrophotometric experiments have been designed and validated to quantify ranolazine hydrochloride (RAN.HCl) in extended-release tablets. The citric acid and sodium citrate are employed as hydrotropes, serving as promising alternatives to polar organic solvents. The development of rapid and specific spectrophotometric experiments aimed at enhancing the spectral absorption of RAN.HCl. The spectrophotometric experiments are D0 and D0 AUC, in which the highest peak absorbance was observed at 270.50 nm, with an AUC ranging from 265.00 to 275.50 nm. Moreover, spectral analysis of D1 and D2 were conducted with peak amplitudes recorded at 280.00 nm and 274.40 nm, respectively. The AUC in the wavelength ranges 275.00–287.00 nm for D1, and 265.00–279.50 nm for D2 were implemented to quantify RAN.HCl confirms no interference from the common additives incorporated into the marketed preparation. The optimized experiments disclosed a linear relationship in the 0.02–0.16 mg/mL concentration range. The accuracy was performed at 50–150 %, revealing an overall average recovery of 100.02 %. The lowest limits of RAN.HCl that could be accurately detected and quantified were 0.0016 and 0.0049, 0.0018 and 0.0055, 0.0058 and 0.0176, 0.0024 and 0.0075, 0.0074 and 0.0224, 0.0021 and 0.0064 mg/mL, respectively, across these investigations. Statistical analysis revealed no significant differences between the outcomes of the present investigation and those documented in literature reports, based on the t- and F-values at p = 0.05, which were below the theoretical values of 2.2622, 2.3646, 6.26, and 19.20, respectively.

Complex Phase Transitions of Fully Rigid Sphere-Rod Amphiphiles Induced by Solvent Polarity in Dilute Solutions.

We report complex macrophase and microphase transitions of rigid amphiphiles with spherical Keggin molecular clusters as the solvophilic block and rod-like rigid oligofluorene (OF) as the solvophobic block in mixed solvents of water and polar organic solvent. By properly adjusting the solvent polarity, the amphiphiles are found to respond accordingly by self-assembling into multilayered incomplete onion-like structures (10-25 vol % THF), single-layered vesicular structures (60 vol % THF), and an unexpected macrophase separation in the middle (40-50 vol % THF), which is due to the anomalous trends in Keggin solubility as a result of the nature of TBA+ counterions. The rigidity of the OF block prevents the amphiphile from assembling by following the rule of packing parameters; instead, interdigitation among different rods leads to the formation of the solvophobic domain to achieve self-assembly. The incomplete onion structures are controlled by the interdigitation of rigid rods for the number of layers and the electrostatic interaction among Keggin head groups for the interlayer distance. When the degree of interdigitation becomes lower, the self-assembly process shows a trend that can be explained by the traditional rule of packing parameter. This study demonstrates the formation of different self-assembled structures by rigid amphiphiles and their transitions induced by solvent composition. The self-assembly (microphase separation) of rigid amphiphiles in a dilute solution could indeed represent a broad area containing complicated, uncharted rules.

Bifunctional self‐segregated electrolyte realizing high‐performance zinc‐iodine batteries

AbstractStatic rechargeable zinc‐iodine (Zn‐I2) batteries are superior in safety, cost‐effectiveness, and sustainability, giving them great potential for large‐scale energy storage applications. However, the shuttle effect of polyiodides on the cathode and the unstable anode/electrolyte interface hinder the development of Zn‐I2 batteries. Herein, a self‐segregated biphasic electrolyte (SSBE) was proposed to synergistically address those issues. The strong interaction between polyiodides and the organic phase was demonstrated to limit the shuttle effect of polyiodides. Meanwhile, the hybridization of polar organic solvent in the inorganic phase modulated the bonding structure, as well as the effective weakening of water activity, optimizing the interface during zinc electroplating. As a result, the Zn‐I2 coin cells performed a capacity retention of nearly 100% after 4000 cycles at 2 mA cm−2. And a discharge capacity of 0.6 Ah with no degradation after 180 cycles was achieved in the pouch cell. A photovoltaic energy storage battery was further achieved and displayed a cumulative capacity of 5.85 Ah. The successfully designed energy storage device exhibits the application potential of Zn‐I2 batteries for stationary energy storage.image

Zero-dimensional hybrid Cu(I) halide with cyan light emission for use in white light emitting diode

Traditional white light-emitting diode (WLED) is mainly depending on coating broadband yellow phosphors (520–700 nm) on blue emitting LED chip (440–460). However, too strong blue light and absence of cyan light results in incongruous emission strength and low color rendering index (CRI), which cause serious damage to retina of eye. To overcome these shortcomings, cyan light emitting phosphor is highly desirable for the full-visible-spectrum LED with high CRI, but bright cyan phosphor remains rare. Herein, a new 0D hybrid copper(I) halide of [TMPDA]Cu2I6 (TMPDA = N,N,2,2-tetramethyl-1,3-propylenediamine) single crystal is reported as a cyan light emitter with mominant emission wavelength at 489 nm, photoluminescence quantum yield of 26.66 % and large Stokes shift of 198 nm exceeding most of organic-inorganic metal halides. Remarkably, the single crystals display stable emission in various polar organic solvents and high temperature with sufficient emitting stability. More significantly, this 0D cuprous halide act as down-conversion cyan phosphor to fabricate WLED with a high CRI of 95 by reducing the cyan gap. In this study, we demonstrate an optical engineering strategy to prepare efficient cyan light emitting 0D cuprous halide and assembly high-performance WLED.

Influence of tree age on the wood color and compounds involved in the “golden-thread” wood color formation in Phoebe zhennan

Wood color plays a key role in the quality and commercial value of wood products. However, the mechanism underlying wood color formation has yet to be fully elucidated. The principal objective of this study was to determine the effects of tree age on the wood color and identify the key metabolites correlated with the golden-thread wood color formation in Phoebe zhennan. The results indicated that the golden-thread wood color of P. zhennan was significantly affected by tree age. Four polar organic solvents and water were tested for the extraction of the metabolites, and ethyl acetate was determined to be the most suitable solvent for the extraction of the golden-thread wood color-related metabolites. Based on the experimental data from the UVVIS-NIR spectral scanning and comparative metabolomics, 66 differentially accumulated metabolites were significantly enriched in older wood, and among these, 46 metabolites (e.g., prenol lipids, carboxylic acids and their derivatives, steroids and their derivatives, and benzene and its substituted derivatives) were closely related to the golden-thread wood color formation (r = 0.526–0.944, P < 0.05). In addition, compared to younger wood (10 years old), older wood (30 and 80 years old) had greater durability and a stronger fragrance because of the enrichment of sesquiterpenoids in older wood. In this study, the effects of tree age on P. zhennan wood color, fragrance, and durability were determined through the alterations in the composition and contents of the related secondary metabolites. These findings contribute to a better understanding of the special wood color formation and can be used for a wide range of applications in the wood industry, from quality control to marketing and product development.

Physicochemical properties and in vitro release of formononetin nano-particles by ultrasonic probe-assisted precipitation in four polar organic solvents

Although formononetin has a considerable biological activity, its therapeutic use is limited by its low solubility. Formononetin was dissolved in ethanol, methanol, N, N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) in this investigation, the antisolvent precipitation procedure with the assistance of an external ultrasonic probe was used to manufacture the formononetin nano-particles. The ideal parameters for response surface BBD optimization are as follows: feed volume flow rate of 6 mL/min; ultrasonic power of 860 W; and liquid-liquid ratio of 1:12.5. The formononetin nano-particles have a smaller particle diameter than raw sample; the lowest size can be as small as (329 ± 1.99) nm, which is 45 times smaller than raw. An in vitro digestion test using a solution that simulated intestinal solution revealed that the release rate of the nano-particle was 1.75 times than that of the raw formononetin. The formononetin nano-particles generated by the aforementioned four solvents have the following order of diameter: ethanol > methanol > DMF > DMSO. This study provided a technical reference for the functional food components in deep processing.

Synthesis of a new unnatural polysaccharide, 2-deoxy-β(1→3)-glucan, by β−1,3-glucan phosphorylase-catalyzed enzymatic polymerization

Abstract We successfully synthesized a new unnatural polysaccharide, 2-deoxy-β(1→3)-glucan, by β−1,3-glucan phosphorylase-catalyzed enzymatic polymerization of a D-glucal monomer from a cellobiose primer, owing to recognition of such non-native substrates by the enzyme. Because of solubility of the product in several high polar organic solvents, acetylation as an example of its derivatizations smoothly occurred using acetic anhydride in the presence of base/catalyst in a DMF solvent. The NMR analysis of the acetylated derivative strongly supported the β(1→3)-linked chain structure.

Microbubble-enhanced cold plasma activation (MB-CPA) for surface functionalization of polymer nanoparticles from nanoprecipitation

Cold plasma activation has been considered as a green and effective technological approach for functionalization of solid surfaces. In the current study, we introduce a versatile technique known as microbubble-enhanced cold plasma activation (MB-CPA) for surface modification of polymer plates and nanoparticles in flowing liquid phase. Corona plasma is generated at the inlet of a venturi tube, thereby creating a highly excited state in the air. Reactive nitrogen and oxygen species (RNOS) are transferred from the gas phase to the suspension flow in the form of plasma microbubbles. Two types of polymer-based nanoparticles in the suspension, namely polymethyl methacrylate (PMMA) of 16–154 nm and polycaprolactone (PCL) of 30–225 nm, are synthesized using nano-precipitation method. Through the degradation of model compounds, the polar organic solvent, acetone and ethanol, is found to promote or suppress the production of active species. In addition, the efficiency of the MB-CPA treatment depends on the solvent composition, making this technology a controllable and efficient strategy for the surface modification of nanoparticles. The findings indicate that plasma activation effectively reduces the negative surface zeta-potentials and induces aggregation and separation in the suspensions. The infrared spectra of the treated nanoparticles reveal that plasma activation leads to the formation of NH and CN bonds situated on the surface of PMMA. Our work demonstrates that organic-solvent involved MB-CPA emerges as a promising method for the surface modification of nanoparticles in the flow condition.

A new luminescent nickel nanocluster with solvent and ion induced emission enhancement toward heavy metal analysis

Expanding the family of fluorescent metal clusters beyond gold, silver, and copper has always been an issue for researchers to solve. In this study, a novel type of cysteine-capped nickel nanoclusters (Cys-Ni NCs) with bright turquoise emission was developed. The as-synthesized Ni NCs showed aggregation-induced emission enhancement (AIEE) properties across Cd2+ and various polar organic solvents. Concurrently, solvents with different viscosities were used to explore the principle of solvent-induced AIEE of Cys-Ni NCs, revealing a positive correlation between fluorescence intensity and solution viscosity. In addition, the concentration of Cd2+ that induced the AIEE effect was reduced by nearly two orders of magnitude in highly viscous solvents, indicating the possibility of Cys-Ni NCs as a promising nanomaterial platform for Cd2+ sensing analysis. Moreover, we propose a novel fluorescent sensing method for rapid detection of Cu2+ based on the carboxyl group of Cys-Ni NCs coupling with Cu2+. Further, validation of Cu2+ detecting methodologies in environmental water samples with the accuracy up to 93.94% underscores their potential as robust and efficient sensing platforms. This study expands the repertoire of fluorescent metal nanoclusters for highly sensitive and selective sensing of hazardous ions and paves the way for further exploration and wide applications in Cu2+ detection in biological and medicine fields.

High Energy Density Asymmetric Tetrathiafulvalene Derivative as a Catholyte for Non-Aqueous Redox Flow Batteries

The inherent intermittency challenge associated with renewable energy sources prompts the rapid development of cost-effective, grid-scale energy storage technologies. Redox flow batteries (RFBs) represent a promising solution to this problem owing to their remarkable potential for scalability and the tunability offered by a wide range of available solution-based chemistries. However, to-date, RFB commercialization has been challenged by a lack of long-lived, energy-dense, and earth abundant charge storage materials. Many of these challenges can be addressed with the development of non-aqueous organic redox flow batteries (NAORFBs). Such batteries leverage the wide potential window (> 5.5 V) offered by organic solvents with the synthetic tunability of organic redox cores to create highly energy dense battery systems with electrolytes based on earth abundant materials (i.e., carbon, nitrogen, sulfur, oxygen, etc.). The energy density of NAORFBs can be optimized with strategies such as increasing the solubility of redoxmers, increasing the number of electrons transferred by redoxmers, and increasing the magnitude of the potential of employed redox materials [1]. Of these, solubility can be enhanced through the grafting of polar side groups to a redoxmer, while redox potential can be increased through the attachment of either electron-withdrawing or donating substituents, in the case of catholyte and anolytes, respectively, near or in conjugation with the redox core [2]. Recently, our group has demonstrated tetrathiafulvalene (TTF) as a robust, two-electron active catholyte material in NAORFBs [3]. Namely, TTF exhibits reversible oxidation events at 0.03 and 0.43 V vs. Ag/Ag+ (Figure 1A). Underivatized TTF, which is highly insoluble in many polar organic solvents, can be made miscible in MeCN, carbonates, and ethereal solvents, with the attachment of four PEG3 chains to the TTF core ((PEG3)2-TTF) (Figure 1B). When paired with a low potential Li metal anode, an RFB incorporating 0.5 M (PEG3)2-TTF (1.0 M e- concentration) in 1.0 M LiPF6-EC/EMC supporting electrolyte exhibits overall operating cell potentials of 3.44 and 3.64 V vs. Ag/Ag+. Here we describe our most recent efforts to develop a further optimized, rationally designed asymmetric TTF derivative – (PEG3/PerF)-TTF – incorporating both a perfluorophenyl ring fused directly to the TTF core and two PEG3 side chains (Figure 1B). The electron-withdrawing perfluorophenyl group functions to substantially raise the potential of both redox events to 0.43 V and 0.65 V vs. Ag/Ag+, while the two PEG3 chains allow the material to retain miscibility in polar solvents. The performance of (PEG3/PerF)-TTF has been successfully demonstrated in a battery at an even higher concentration of 0.75 M (1.5 M e- concentration) (Figure 1C). When also paired with a Li metal anode in 1.0 M LiPF6-EC/EMC supporting electrolyte, the battery exhibits exceptional operational energy density of 96 Wh/L at 6 mA/cm2 current density and capacity retention of 83.1% over 16.8 d of continuous operation (99.0% per d). These results further demonstrate TTF as a highly versatile catholyte with remarkable potential for application in NAORFBs.

Mechanism simulation of polar and nonpolar organic solvent vapor adsorption on a multiwall carbon nanotubes paper gas sensor.

We investigate the adsorption behavior of polar and nonpolar molecules on carbon nanotube interfaces through computational simulations. Gaussian 16 was utilized to calculate the total energy of each possible molecular structure and analyze the adsorption mechanisms in stacked and inline configurations. The study reveals that nonpolar molecules favor stacked adsorption on two graphene interfaces, while polar molecules prefer inline adsorption. The findings suggest that inline adsorption of polar molecules results in minimal changes to the local dielectric constant, which may explain the absence of multi-step adsorption isotherms. The research examines the stability and energetics of molecular adsorption on graphene layers simulating CNT interfaces. Different types of molecules (polar and nonpolar) exhibit distinct adsorption behaviors, with nonpolar molecules aligning with the IUPAC type VI isotherm model and polar molecules following the Langmuir isotherm model (IUPAC type I). This study provides insight into how molecules are likely to adsorb on CNT surfaces and the impact on the local dielectric constant. This understanding has implications for the design and optimization of CNT-based sensors, particularly in detecting organic solvents and gases in various environments.

Fabrication of a family of porous azo polymers with multifunctional adsorption and separation performances

In this paper, a class of porous organic polymers (POPs) of p-hydroxy azobenzene with a mesoporous structure was designed and synthesized by a –NN– coupling reaction of tetraamino-metal phthalocyanine (MTAPc, where M = Co, Ni or Cu) with hydroquinone (namely Azo-MHQ, where M = Co, Ni or Cu). The Azo-MHQ materials possessed good thermal stabilities, excellent dispersibilities in water, polar and non-polar organic solvents, as well as excellent chemical stabilities. Among them, Azo-CuHQ showed an outstanding iodine trapping ability in an iodine solution and vapor with saturated adsorption capacities of 1347.47 mg g−1 and 118 wt%. In addition, Azo-CuHQ also showed a high adsorption capacity for methylene blue (MB) with the adsorption amount of 191.21 mg g−1. Furthermore, by loading Azo-CuHQ onto polyethersulfone (PES) membrane, the water permeability of the obtained membranes reached 147.03 L m−2 h−1 bar−1, and the retention rate of Ag in a very low concentration solution of 20 ppm was 56.8 %. Additionally, a thorough analysis of the Azo-CuHQ adsorption and separation mechanism was conducted. A novel approach to the design and synthesis of a class of materials with multifunctional adsorption and separation capabilities is presented in this research.

Evaluation of analytical columns suitable for high-temperature liquid-chromatography-isotope-ratio-mass-spectrometry analysis of anabolic steroids

Isotope ratio mass spectrometry (IRMS) can be used to determine the carbon isotope ratio of anabolic steroids. For example, in sports doping and food safety control, it enables determining an endogenous or synthetic origin of anabolic steroids. Generally, the steroids of interest are purified by liquid chromatography (LC) and analysed by gas chromatography combustion IRMS. LC-IRMS is not used since only mobile phases without carbon atoms can be used. For analysing mid-to apolar compounds, heated water can be used as an eluent as it has a similar polarity to a weak polar organic solvent. The silica-based columns are not robust enough at elevated temperatures in aqueous conditions. However, modified silica particles, metal oxides coated with polymers, and porous graphitic carbon are promising column materials for high-temperature LC (HT-LC) applications. Here, the stability of the stationary phase is crucial, and their chromatographic performance needs to be evaluated under the conditions mentioned above for anabolic steroid separations. Six columns using temperatures up to 200 °C were assessed, and only two were found to be appropriate. The ZirChrom-PBD column can be used for HT-LC-IRMS research purposes but is not recommended for routine laboratory practice applications due to the substantial loss of retention and resolution over time at elevated temperatures. Sachtopore-RP columns are the only suitable option for routine HT-LC-IRMS applications, even though they suffer from peak broadening over time when operating at elevated temperatures

Investigating Cellulose Nanocrystal and Polyvinyl Alcohol Composite Film in Moisture Sensing Application

This study focused on utilizing cellulose nanocrystal (CNC)–polyvinyl alcohol (PVA) composite in optical sensor applications to detect high humidity conditions and determine water concentration in ethanol. We focused on the composite’s effectiveness in moisture absorption to demonstrate visual color change. We demonstrated that the different molecular weights of PVA significantly affect CNC’s chiral nematic structure and moisture absorption capability. PVA with molecular weight 88 k–97 k exhibited the disintegration of its chiral nematic structure at 30 wt%, whereas low molecular weight PVA (n~1750) showed no structural disintegration even at 100 wt% concentration when analyzed through UV-Vis spectroscopy. Further, the thermal crosslinking of the CNC-PVA composite showed no significant loss of moisture sensitivity for all molecular weights of the PVA. We observed that the addition of PVA to the sulfated CNC obtained from sulfuric acid hydrolysis did not facilitate moisture absorption significantly. A CNC-PVA sensor was developed which can detect high humidity with 2 h. of exposure time. 2,2,6,6-tetramethylpiperidin-1-piperidinyloxy oxidized CNC (TEMPO-CNC) having carboxylic functionality was also used to prepare the CNC-PVA composite films for comparing the effect of functional groups on moisture sensitivity. Finally, we demonstrated a facile method for utilizing the composite as an optical sensor to detect water concentration in ethanol efficiently; thus, it can be used in polar organic solvent dehydration applications.

Synthesis of the polyethylene polyamine-based flexible covalent organic frameworks and their application for capturing and fluorescence sensing iodine

Effective uptake of radioactive steam waste in the fission process is of great vital for the safe use of nuclear energy. Nitrogen-rich polyethylenepolyamine provides effective adsorption sites for the capture of iodine, but triethylenediamine (TEDA)-impregnated activated carbon has the disadvantages of easy sublimation, poor safety, and poor regeneration capacity. Herein, we report five polyethylene polyamine-based (PEPA-based) flexible COFs for the first time which were synthesized by Schiff base polymerization reactions with the flexible knot [2,4,6-tris(4-formylphenoxy)-1,3,5-triazine (TPT–3–CHO)] and flexible linkers (PEPA). The PEPA-based flexible COFs possess large surface areas and strong iodine adsorption capacity, which can be reused. With the increase of the linker lengths, their BET-surface areas decreases, but their adsorption of iodine increase. When dispersed in polar organic solvents, the PEPA-based flexible COFs can fluorescently sense iodine through the electron transfer mechanism and the energy transfer mechanism.

Synthesis and properties of N-(2,2,2-tribromoethylidene)-4-chlorobenzenesulfonamide

The present work continues a systematic study to find efficient and accessible methods for the synthesis ofN-sulfonylimines of polyhaloaldehydes and to analyze their properties. In the reaction of N,N-dichlorobenzene sulfon-amide with tribromoethylene, N-(2,2,2-tribromoethylidene)amide of 4-chlorobenzenesulfonic acid was obtained for the first time with a quantitative yield at boiling water bath temperature in carbon tetrachloride medium. The infrared spectra of N-(2,2,2-tribromoethylidene)-4-chlorobenzenesulfonamide reveal the absorption bands of sulfonic (1360 and 1165 cm-1) and NH (3275 cm-1) groups, while the 1H NMR spectra show a signal for azomethine protons within the region of 8.3–8.6 ppm. The 13C NMR spectra exhibit a signal for the CBr3 group within the region of ~31–43 ppm, while the signal characteristic of the CBr2Сl group within the region of ~53–56 ppm is absent. This means that no imine of dibromochloroacetic aldehyde is formed during the reaction. Thus, an efficient method for the synthesis of N-(2,2,2-tribromoethylidene)-4-chlorobenzenesulfonamide was developed, and the chemoselectivity of this reaction was found to depend on the process temperature. It was shown that N-(2,2,2-tribromoethylidene)-4-chlorobenzenesulfonamide has amidoalkylating properties. A reaction of N-(2,2,2-tribromoethylidene)-4-chlorobenzenesulfonamide with benzene, toluene, anisole, and 2-chlorothiophene in the presence of an acid catalyst yielded p-substituted aromatic derivatives and 2,5-substituted thiophene derivatives. Infrared spectroscopy and NMR spectroscopy (1H, 13C) revealed that the substitution reaction proceeds regioselectively. All the obtained products were isolated in pure form as powders soluble in polar organic solvents and insoluble in water. The yields of 4-chloro-N-(1-phenyl-2,2,2-tribromoethyl)-benzenesulfonamide, 4-chloro-N-[1-(4-methylphenyl)-2,2,2-tribromoethyl]-benzenesulfonamide, 4-chloro-N-[1-(4-methoxyphenyl)-2,2,2-tribromoethyl]-benzene-sulfonamide, and 4-chloro-N-[2,2,2-tribromoethyl-1-(5-chloro-2-thienyl)ethyl]-benzenesulfonamide amounted to 74, 72, 64, and 74 %, respectively.