Anion Selectivity of Tetravalent Tin Compounds in Membranes Studied by 119Sn-, 13C- and 1H-NMR

The fundamental molecular aspects of trialkyltin compounds of the type R₃SnY have been investigated in view of their applicability as ion-selective components in solvent polymeric membranes. The interaction between these compounds and anions has been studied using ¹¹⁹Sn- and ¹³C-NMR. Neutral tetracoordinated trialkyltin compounds form a negatively charged pentacoordinated complex upon interaction with Cl-ions in homogeneous organic phases as well as in membranes in contact with aqueous solutions. Although in a homogeneous phase, the electronegative substituent Y determines the complex-formation constant, it has no influence on the potentiometric anion selectivity in liquid membranes containing trialkyltin carriers R₃SnY with different Y. The observed selectivity pattern is not given by the magnitude of the stability constants in a homogeneous phase but is dictated by the prevailing association-dissociation process leading to tetracoordinated compounds which change in constitution due to varying sample composition, The results obtained from equilibrium studies of tetravalent mono tin compounds with anions in both homogeneous phase and in two-phase systems confirm the earlier hypothesis that trialkyltin compounds incorporated in solvent polymeric membranes act as electrically neutral carriers for anions.     

碱性阴离子交换聚合物膜研究进展

碱性燃料电池(AFCs)是一种直接将化学能转化为电能的发电装置,因其高效、环保等优点,得到了科学界与工业界的广泛关注。阴离子交换聚合物膜作为碱性阴离子交换膜燃料电池的核心组成部分,要求其具备优异的电导率、良好的化学稳定性及力学强度。本文主要从聚合物主链及阳离子官能团的结构与性能之间的关系及调控方式方面,综述了碱性阴离子交换膜的研究进展。     

Specific Selectivity of Modified Ion-Exchange Membranes

Effective transfer numbers through homogeneous membranes MK-100 and polyethylene diamine-modified membranes MK-100M are measured. A mathematical model for the membranes is considered. The presence of a modified surface is accounted for by introducing phenomenological conductivity coefficients. The effect of the solution composition, overall concentration, and current density on competitive transfer is analyzed. The modified layer has a pronounced effect on the membrane specific selectivity at low current densities and only slightly affects it in a limiting state.     

Concentration Polarization and Specific Selectivity of Membranes in Pulse Mode

Nonstationary concentration polarization of membranes was analyzed theoretically. Desalination and transport of single- and double-charged ions through MK-40 cation-exchange membrane was studied in the stationary and pulse modes with the fixed voltage. Main generalities in the changes of the pH and conductivity of desalinated solution as well as concentrations of single- and double-charged ions as the functions of solution flow velocity, voltage, frequency and off-duty ratio of pulses were established.     

Anion Selectivities of Triorganyltin Acetates and Halides in Solvent Polymeric Membranes

A series of triorganyltin compounds of the type R₃SnY and RR²SnY has been studied in view of their anion selectivities exhibited in solvent polymeric membranes. A large variety of selectivity patterns has been observed first by varying the concentration of a given ionophore in the membrane phase, and second by using ionophores which differ in the organic substituents R on the Sn centre. With more space consuming substituents R, the observed selectivity patterns become more and more similar to that of a blank membrane, suggesting steric hindrance for the pentacoordination of the corresponding ionophores by sample anions.     

Hydroxy Groups Enhance [2]Rotaxane Anion Binding Selectivity

We report the synthesis of two [2]rotaxanes containing an interlocked three dimensional binding cavity formed from a pyridinium bis(amide) axle component containing two phenol donors, and an isophthalamide based macrocycle. In the competitive solvent mixture 1 : 1 CDCl₃ : CD₃OD, one of the receptors exhibits a much higher selectivity preference for chloride than an analogous rotaxane without the hydroxy groups. X-ray crystal structures reveal the chloride anion guest encapsulated within the interlocked binding cavity, though not all of the hydrogen bond donors are utilised. Computational semi-empirical simulations indicate that secondary intermolecular interactions occur between the axle hydroxy hydrogen bond donors and the [2]rotaxane macrocycle components, contributing to a more preorganised binding pocket, which may be responsible for the observed enhanced selectivity.     

Novel Anion Exchangers for Electrodes with Improved Selectivity to Divalent Anions

It has been found that replacing of several long‐chain alkyl substituents at the nitrogen atom of lipophilic quaternary ammonium salts (QAS) by methyls results in a dramatic increase of the potentiometric selectivity of ion‐selective electrodes (ISE) with QAS‐based plasticized PVC membranes to some divalent anions against the monovalent ones. The discussed effect of QAS cation nature on the potentiometric selectivity is also partly retained for ISE with neutral carrier‐based membranes doped with QAS to provide anion permselectivity. This opens up new possibilities to control the potentiometric selectivity of ISE for divalent anions by the appropriate selection of the anion exchanger.     

Poly(Ethylene Piperidinium)s for Anion Exchange Membranes

The lack of anion exchange membranes (AEMs) that possess both high hydroxide conductivity and stable mechanical and chemical properties poses a major challenge to the development of high-performance fuel cells. Improving one side of the balance between conductivity and stability usually means sacrificing the other. Herein, we used facile, high-yield chemical reactions to design and synthesize a piperidinium polymer with a polyethylene backbone for AEM fuel cell applications. To improve the performance, we introduced ionic crosslinking into high-cationic-ratio AEMs to suppress high water uptake and swelling while further improving the hydroxide conductivity. Remarkably, PEP80-20PS achieved a hydroxide conductivity of 354.3 mS cm⁻¹ at 80 °C while remaining mechanically stable. Compared with the base polymer PEP80, the water uptake of PEP80-20PS decreased by 69 % from 813 % to 350 %, and the swelling decreased substantially by 85 % from 350.0 % to 50.2 % at 80 °C. PEP80-20PS also showed excellent alkaline stability, 84.7 % remained after 35 days of treatment with an aqueous KOH solution. The chemical design in this study represents a significant advancement toward the development of simultaneously highly stable and conductive AEMs for fuel cell applications.     

Tuning Selectivity and Sensitivity of Mixed‐polymeric Tetraruthenated Metalloporphyrins Modified Electrodes as Voltammetric Sensors of Chloramphenicol

Mixed Ni?Co tetraruthenated porphyrin films were successfully electropolymerized on glassy carbon electrodes in alkaline solutions (pH=13) of NiTRP and CoTRP, giving excellent electrocatalytic responses for determination of the antibiotic drug chloramphenicol. Electrodes with four different compositions were obtained by varying the ratio of NiTRP and CoTRP in the deposition solution. For the characterization of these materials, SEM, ICP‐MS, EIS and CV were explored. The porphyrin modified glassy carbon electrodes presented two oxidation peaks for chloramphenicol (except for Ni‐25). The potential shifted to lower values as the percentage of CoTRP increased decreasing its oxidation potential in more than 200 mV for Ni‐50 as compared to Ni‐100. Interestingly, the materials with cobalt content larger than 50 % did not show the typical catalytic response of the Ni^IIIOOH species, but rather showed an increase in current at potentials larger than 0.4 V, demonstrating the key role played by nickel in this type of materials. The composition of polymeric mixed porphyrin materials influenced the oxidation current response of both redox waves, resulting in different sensitivities on the calibration curves.     

金属卟啉类化合物的合成

金属卟啉;次卟林(Ⅸ)二甲酯;（乙酰基）次卟啉(Ⅸ)二甲酯     

Direct Insertion Polymerization of Ionic Monomers: Rapid Production of Anion Exchange Membranes

The limited number of methods to directly polymerize ionic monomers currently hinders rapid diversification and production of ionic polymeric materials, namely anion exchange membranes (AEMs) which are essential components in emerging alkaline fuel cell and electrolyzer technologies. Herein, we report a direct coordination-insertion polymerization of cationic monomers, providing the first direct synthesis of aliphatic polymers with high ion incorporations and allowing facile access to a broad range of materials. We demonstrate the utility of this method by rapidly generating a library of solution processable ionic polymers for use as AEMs. We investigate these materials to study the influence of cation identity on hydroxide conductivity and stability. We found that AEMs with piperidinium cations exhibited the highest performance, with high alkaline stability, hydroxide conductivity of 87 mS cm⁻¹ at 80 °C, and a peak power density of 730 mW cm⁻² when integrated into a fuel cell device.     

Metalloporphyrins in macromolecular chemistry

The review presents an analysis of the data on the synthesis of metalloporphyrin-based polymers of different structure. Manufacturing coordination polymers via extra coordination of small molecules and fragments of high-molecular-weight compounds by porphyrin metal complexes are discussed. The main approaches to the development of functional materials based on these polymers are summarized.     

Study of the Selectivity of SnO2 Supported Membranes Prepared by a Sol-Gel Route

In this work the sol-gel process was used to prepare SnO2 supported membranes with an average pore size of 2.5 nm. The effects of salt concentration (NaCl or CaCl2) and of the pH of the aqueous solutions used on the flux and selectivity through the SnO2 membrane were analyzed by permeation experiments and the results interpreted taking account of the zeta potential values determined from the electrophoretic mobility of the SnO2 powder aqueous dispersion. The results show that the ion flux (Na+, Ca2+ and Cl–) throughout the membrane is determined by the electrostatic repulsion among these species and the surface charge at the tin oxide-solution interface.     

Tuning the Selectivity of Biodegradable Antimicrobial Cationic Polycarbonates by Exchanging the Counter‐Anion

There is a growing interest in modern healthcare to develop systems able to fight antibiotic resistant bacteria. Antimicrobial cationic biodegradable polymers able to mimic antimicrobial peptides have shown to be effective against both Gram‐positive and Gram‐negative bacteria. In these systems, the hydrophilic–hydrophobic ratio and the cationic charge density play a pivotal role in defining the killing efficiency. Nevertheless, many of these antimicrobial polymers show relatively low selectivity as defined by the relative toxicity to mammalian cells or hemolysis relative to pathogens. In this study, a series of polycarbonates containing pendant quaternary ammoniums are used to understand the role of different counter‐anions including chloride, citrate, malonate, benzoate, acetate, lactate and trifluoroacetate, and the antibiotic penicillin on antimicrobial efficacy and selectivity. Interestingly, it is found that in spite of the strong antimicrobial activity of trifluoroacetate and benzoate anions, they prove to be much less hemolytic than chloride anion. It is believed that the proper selection of the anion could enhance the potential of antimicrobial polymers to fight against clinically relevant pathogenic infections, while concurrently mitigating harmful side effects.

     

扑热息痛分子印迹聚合物膜选择性结合和渗透性质的研究

采用紫外光引发原位聚合的方法制备了具有支撑膜的扑热息痛分子印迹聚合物膜. 紫外分光光度法证明了模板分子与功能单体之间存在相互作用, 并据此选择了聚合反应时合适的溶剂. 用傅立叶红外光谱和扫描电镜分别测定了膜的结构和表面形貌. 渗透实验结果表明渗透时所用溶剂对渗透结果有重要影响. 合适的渗透溶剂可提高印迹膜对模板分子的渗透选择性.     

Anion Exchange Membranes Based on Chloromethylation of Fluorinated Poly(arylene ether)s

This report details the properties of fluorine-containing anion exchange membranes(AEMs) synthesized by chloromethylation and quaternization of fluorinated poly(arylene ether)s(FPAEs) based on decafluorobiphenyl and bisphenol A. Meanwhile, we compared their properties with those of their non-fluorinated counterparts, Udel-based AEMs. The reactivity of the chloromethylation of fluorinated poly(arylene ether)s was lowered by the strong electron-withdrawing group, per-fluorinated biphenyl residue. Therefore higher temperature, more chloromethylation reagent, and longer reaction time were needed in the chloromethylation of FPAEs. Because of the hydrophobicity of fluorine, the swelling of FPAEs was depressed. In the FPAE-based AEMs, the water uptake of FPAE-1 membrane(F-1) was just 30%. There is a strong correlation between water uptake and conductivity for both Udel- and FPAE-based AEMs. Among all the membranes, the water uptake and the conductivity of FPAE-3 membrane(F-3) could reach up to 100% and 13.47 mS/cm respectively at 30 ℃. The mechanical properties of FPAE-based AEMs at room temperature were worse than those of Udel-based ones because of the weak intermolecular interaction caused by the low polarizability of fluorine. However, their high temperature mechanical properties are better, which can be explained in terms of low swelling.     

Pore Modification in Porous Ceramic Membranes With Sol-Gel Process and Determination of Gas Permeability and Selectivity

Summary: The aim of the study was to investigate the variation in total surface area, porosity, pore size, Knudsen and surface diffusion coefficients, gas permeability and selectivity before and after the application of sol-gel process to porous ceramic membrane in order to determine the effect of pore modification. In this study, three different sol-gel process were applied to the ceramic support separately; one was the silica sol-gel process which was applied to increase porosity, others were silica-sol dip coating and silica-sol processing methods which were applied to decrease pore size. As a result of this, total surface area, pore size and porosity of ceramic support and membranes were determined by using BET instrument. In addition to this, Knudsen and surface diffusion coefficients were also calculated. After then, ceramic support and membranes were exposed to gas permeation experiments by using the CO₂ gas with different flow rates. Gas permeability and selectivity of those membranes were measured according to the data obtained. Thus, pore surface area, porosity, pore size and Knudsen diffusion coefficient of membrane treated with silica sol-gel process increased while total surface area was decreasing. Therefore, permeability of ceramic support and membrane treated with silica sol-gel process increased, and selectivity decreased with increasing the gas flow rate. Also, surface area, porosity, pore size, permeability, selectivity, Knudsen and surface diffusion coefficients of membranes treated with silica-sol dip coating and silica-sol processing methods were determined. As a result of this, porosity, pore size, Knudsen and surface diffusion coefficients decreased, total surface area increased in both methods. However, viscous flow and Knudsen flow permeability were detected as a consequence of gas permeability test and Knudsen flow was found to be a dominant transport mechanism in addition to surface diffusive flow owing to the small pore diameter in both methods. It was observed that silica-sol processing method had lower pore diameter and higher surface diffusion coefficient than silica-sol dip coating method.