Electroinitiated Polymerization of N-Vinylcarbazole by Direct Electron Transfer

Electroinitiated polymerization of N-vinylcarbazole has been accomplished by constant potential electrolysis. It was found that direct electron transfer from the monomer to the anode initiates the polymerization even at a potential as low as +0.95 V versus Ag^?/ Ag⁺. Dichloromethane was used as the solvent, and the electrolyte was tetrabutylammonium fluoroborate. Conversions as high as 86% were reached even when a microelectrode was used. Effects of electrode area, temperature, and electrode potential on polymerization were studied. Percent conversion was followed by cyclic voltammetry.     

Polymeric Nitrofuran Derivatives. II. Chemical Modification of Functionalized Resins with Nitrofuran Derivatives

Polymeric nitrofuran derivatives have been synthesized by chemical modification of macroporous styrene-divinylbenzene copolymers with low molecular weight nitrofurans. The 5-nitrofuryl groups are covalently attached to the polymeric carrier by azomethine, ester, N-alkyl, and sulfamide links, respectively. Comparative hydrolysis studies and biological tests of the modified resins suggested that the polymeric carrier-bound nitrofurans are antimicrobially active. The polymeric nitrofurans have been characterized by IR and “C-solid-NMR spectroscopy”.     

非共价键交联海藻酸钠水凝胶的制备与性能

天然多糖海藻酸钠制备的水凝胶具有优越的生物相容性和生物组织相似性,作为生物医用材料在药物控制释放、组织工程支架、抗菌材料及创伤敷料等领域发挥着越来越大的作用。本文在介绍海藻酸钠物化性质的基础上,重点综述了非共价键交联(静电作用、氢键、范德华力、亲疏水作用等)海藻酸钠水凝胶的制备方法以及性能表征方法,最后讨论了制备方法及性能表征研究中的一些需要解决的问题。     

Preparation and characterization of a conductive polyaniline/polysulfone film and evaluation of the effect of co-solvent

A novel conductive dense membrane composed of polyaniline (PANI) and polysulfone (PSU) was prepared. To improve the solubility of PANI in N-methyl pyrrolidone (NMP) and consequently increase the conductivity of the eventual film, a tertiary amine (1,3-dimethyl-2-imidazolidinone, DMI) was added to the solvent as a co-solvent. Different PANI solution concentrations in NMP/DMI were used to make blend films via solution blending with PSU solution in NMP in different ratio’s of PANI/PSU. The effect of the PSU fraction on the properties of the membrane has been investigated. The electrical conductivity, doping degree, crystallinity, miscibility of the polymers and shape stability were investigated. It was observed that an increase in the PSU fraction causes a decrease in the conductivity as well as less film deformation after doping. The conductivity and shape stability of the blend film were optimized by a change in PANI concentration in the casting solution and a change in the PSU fraction. The best conductivity was achieved using 3% PANI solution in NMP/DMI and the minimum percentage of PSU, allowing good shape stability after doping, was found to be 40%.     

Pervaporation separation of water + 1,4-dioxane and water + tetrahydrofuran mixtures using sodium alginate and its blend membranes with hydroxyethylcellulose—A comparative study

Sodium alginate and hydroxyethylcellulose blend membranes were prepared by solution casting, crosslinked with glutaraldehyde and urea–formaldehyde–sulfuric acid mixture. Crosslinking was confirmed by Fourier transform infrared spectroscopy, while the blend compatibility was studied by differential scanning calorimetry and scanning electron microscopy. Membranes were tested for pervaporation separation of feed mixtures ranging from 10 to 50 mass% water in water + 1,4-dioxane and water + tetrahydrofuran mixtures at 30 °C. For 10 mass% of the feed mixture, pervaporation experiments were also carried out at higher temperatures (40 and 50 °C). By increasing the temperature, a slight increase in flux with a considerable decrease in selectivity was observed for all the membranes and for both the mixtures. The blend membranes exhibited different pervaporation performance for both the binary mixtures investigated. For water + 1,4-dioxane mixture, the pervaporation performance did not improve much after blending, whereas for water + tetrahydrofuran mixture, the pervaporation performance has improved considerably over that of plain sodium alginate membrane.     

Reducing Antioxidant Capacity Evaluated by Means of Controlled Potential Electrolysis

An analytical method suitable for an antioxidant sensor is presented following the response of these substances to an extensive oxidation imposed by electrochemical means. The electrochemical assay simulates the action of a reactive oxygen species (ROS) by means of electrolyses carried out at a potential which is settled at the formal potential of the ROS. The antioxidant activities of trolox and ascorbic, gallic and caffeic acids and of mixtures of these antioxidants were estimated from the charge required for the complete oxidation of the antioxidants from assays where the oxidative attack by O₂ and by O₂^.? were simulated.     

Interaction of collagen and poly(vinyl pyrrolidone) in blends

The interaction between collagen and poly(vinyl pyrrolidone) (PVP) in blends has been studied by viscometry, differential scanning calorimetry (DSC) and by Fourier transform infrared spectroscopy (FTIR). It was found that the amide A and amide I bands position in FTIR spectra of collagen were shifted after blending with PVP to higher wavenumbers. DSC measurements showed different melting temperature, glass transition temperature and enthalpy for the blends and for the single components. Viscosity measurements showed interaction between collagen and PVP also in a dilute water solution.The results have shown, that the interactions between collagen and PVP exist due to the strong interactions between the synthetic and biological component, mainly by hydrogen bonds. These interactions caused that collagen and PVP are miscible at molecular level. The blending of collagen with PVP may give the possibility of producing new materials for potential biomedical applications.     

Characterization and properties of biodegradable poly(hydroxyalkanoates) and 4,4-dihydroxydiphenylpropane blends: Intermolecular hydrogen bonds, miscibility and crystallization

Intermolecular hydrogen bonds, miscibility, crystallization and thermal stability of the blends of biodegradable poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-3HHx)] with 4,4-dihydroxydiphenylpropane (DOH₂) were investigated by FTIR, ¹³C solid state NMR, DSC, WAXD and TGA. Intermolecular hydrogen bonds were found in both blend systems, which resulted from the carbonyl groups in the amorphous phase of both polyesters and the hydroxyl groups of DOH₂. The intermolecular interaction between P(3HB-3HHx) and DOH₂ is weaker than that between PHB and DOH₂ owing to the steric hindrance of longer 3HHx side chains. Because of the effect of the hydrogen bonds, the chain mobility of both PHB and P(3HB-3HHx) components was limited after blending with DOH₂ molecules. Single glass transition temperature depending on the composition was observed in all blends, indicating that those blends were miscible in the melt. The addition of DOH₂ suppressed the crystallization of PHB and P(3HB-3HHx) components. Moreover, the crystallinity of PHB and P(3HB-3HHx) components also decreased with increasing DOH₂ content in the blends. However, the crystal structures of the crystallizable components were not affected. The existence of DOH₂ favors to thermal decomposition of PHB and P(3HB-3HHx) components, resulting in the decrease in thermal decomposition temperature.     

Hydrogen Transfer Polymerization Mechanism of Acrylamide Induced by Propagating Polyacrolein Anion

In order to investigate the interaction between acrolein (AL) and acrylamide (AAm) on anionic copolymerization, the homopolymer-izabilities of AL in the presence of several p-substituted phenyl-acetamides such as p-nitroacetanilide, p-chloroacetanilide, acet-anilide, and p-methylacetanilide were investigated in tetrahydro-furan at 0°C using imidazole as an anionic catalyst. A linear co-relation was obtained by Hammett′ s equation as described by log R /R = 0.28σ. This result suggests that the homopolymeriz- P Po ability of AL is influenced by the structure of the amide compound. An increase of the additive propionamide (PAm) on the homopolym-erization of AL induced by the pyridine-water initiation system increased the polymerization rate R; however, it decreased the intrinsic viscosity [η] of poly-AL. From the measurement of infrared spectroscopy and elementary analysis, the presence of a chain transfer reaction between the poly-AL anion and PAm was found. These results support the presence of interaction between AL and AAm derivatives in the copolymerization system.     

多组分聚合物体系中的相容和络合

在含可控特殊相互作用的多组分聚合物体系中，随着体系中的相互作用密度的增强，体系在本体中可经历由不相容到相容直至络合的不同物理状态。本文概述了相容、络合研究的进展，着重讨论了相容和络合的区别和联系，提出了含氢键相互作用的高分子共混体系中相容－络合转变存在的普遍性。     

Controlled Radical Polymerization of N-Vinylpyrrolidone by Reversible Addition-Fragmentation Chain Transfer Process

Summary: Poly(N-vinylpyrrolidone) (PNVP) was polymerized by RAFT process using diphenyldithiocarbamate of diethylmalonate (DPCM) as the reversible chain transfer agent in the presence of a small percentage of a conventional radical initiator (AIBN). The molar mass of the polymers synthesized by this method was found to increase with conversion and time. The presence of end group in the polymer chain could be confirmed by ¹H NMR spectra. The molar masses calculated using ¹H NMR spectroscopy and static light scattering (SLS) showed good agreement with the theoretical molar masses. The RAFT compound was fully consumed during the initial stages of the polymerization itself. The controlled nature of these polymers was further confirmed by generating diblock copolymers by sequential addition of monomers such as styrene or n-butyl acrylate (n-BA). PNVP efficiently participated as a macro-RAFT reagent, and cross-over reaction between the two blocks efficiently occurred. The successful diblock copolymer synthesis using PNVP as macro-transfer reagent further confirms the “controlled” nature of such synthetic procedure.     

Integration of CuAAC Polymerization and Controlled Radical Polymerization into Electron Transfer Mediated “Click‐Radical” Concurrent Polymerization

The successful chain‐growth copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) polymerization employing Cu(0)/pentamethyldiethylenetriamine (PMDETA) and alkyl halide as catalyst is first investigated by a combination of nuclear magnetic resonance, gel‐permeation chromatography, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. In addition, the electron transfer mediated “click‐radical” concurrent polymerization utilizing Cu(0)/PMDETA as catalyst is successfully employed to generate well‐defined copolymers, where controlled CuAAC polymerization of clickable ester monomer is progressed in the main chain acting as the polymer backbone, the controlled radical polymerization (CRP) of acrylic monomer is carried out in the side chain. Furthermore, it is found that there is strong collaborative effect and compatibility between CRP and CuAAC polymerization to improve the controllability.

     

海藻酸钠/水性聚氨酯共混膜的结构表征和性能测试

本文将海藻酸钠与聚酯型水性聚氨酯共混制膜，并通过红外光谱（FTIR）、X射线衍射（XRD）、扫描电镜（SEM）、紫外光谱（UV）、力学性能测试对共混膜的结构和性能进行了表征与测试。结果表明，共混膜中两种分子间存在着强烈的相互作用和良好的相容性，与纯海藻酸钠膜相比共混膜有较高的抗水性和断裂伸长率。     

碳纳米管促进氧化还原蛋白质和酶的直接电子转移

将血红蛋白(Hb)、辣根过氧化物酶(HRP)和葡萄糖氧化酶(GOx)分别固定在经碳纳米管修饰的玻碳电极(CNT/GC)上,制成Hb CNT/GC、HRP CNT/GC和GOx CNT/GC电极.Hb、HRP和GOx在CNT/GC电极表面均能发生有效和稳定的直接电子转移反应,其相应的循环伏安曲线均显示出一对几近对称的氧化还原峰;在60mV/s下,其式量电位E0'分别为-0.343V、-0.319V和-0.456V(vs.SCE,pH6.9),且不随扫速而变;以上三者在CNT/GC电极表面直接电子转移的表观速率常数ks依次为1.25±0.25、2.07±0.56和1.74±0.42s-1;根据式量电位E0'随缓冲溶液pH值的变化关系,确知在CNT/GC电极上,Hb或HRP发生的直接电化学遵从(1e+1H+)电极过程机理,而GOx发生的直接电化学反应则遵从(2e+2H+)机理.此外,固定在CNT/GC电极表面的Hb、HRP和GOx也同时表现出对各自底物的生物电催化活性.由本文制备的碳纳米管修饰电极及其固定生物蛋白质(酶)的方法具有简单、易于操作等优点,并可用于对其它生物氧化还原蛋白质和酶的直接电子转移测试.     

Proton Transfer Influence on Geometry and Electron Density in Benzoic Acid–Pyridine Complexes

The influence of the proton transfer on the geometry of donor and acceptor molecule in benzoic acid–pyridine complexes is investigated by theoretical calculations at the B3LYP/6‐311++G** level of theory. Systematic shifts of the H‐atom in the H‐bond are reflected in the geometry of the COOH group and the lengths of aromatic ring bond lengths of the proton acceptor. Changes in electron densities have been studied by atoms in molecules analysis. A systematic natural bond orbital analysis has been performed to study the proton transfer mechanism. Two donor orbitals are engaged in the proton transfer process which is accompanied by a change in orbital delocalization of H‐atom that can switch between two donor orbitals so the path of proton transfer in intermolecular H‐bond is not determined by the orbital shape. Theoretical results have been confirmed by experimental results published previously.     

Photobiocatalysis: Activating Redox Enzymes by Direct or Indirect Transfer of Photoinduced Electrons

Biocatalytic transformation has received increasing attention in the green synthesis of chemicals because of the diversity of enzymes, their high catalytic activities and specificities, and mild reaction conditions. The idea of solar energy utilization in chemical synthesis through the combination of photocatalysis and biocatalysis provides an opportunity to make the “green” process greener. Oxidoreductases catalyze redox transformation of substrates by exchanging electrons at the enzyme′s active site, often with the aid of electron mediator(s) as a counterpart. Recent progress indicates that photoinduced electron transfer using organic (or inorganic) photosensitizers can activate a wide spectrum of redox enzymes to catalyze fuel‐forming reactions (e.g., H₂ evolution, CO₂ reduction) and synthetically useful reductions (e.g., asymmetric reduction, oxygenation, hydroxylation, epoxidation, Baeyer–Villiger oxidation). This Review provides an overview of recent advances in light‐driven activation of redox enzymes through direct or indirect transfer of photoinduced electrons.     

Regulation of the Cyanobacterial Circadian Clock by Electrochemically Controlled Extracellular Electron Transfer

There is growing awareness that circadian clocks are closely related to the intracellular redox state across a range of species. As the redox state is determined by the exchange of the redox species, electrochemically controlled extracellular electron transfer (EC‐EET), a process in which intracellular electrons are exchanged with extracellular electrodes, is a promising approach for the external regulation of circadian clocks. Herein, we discuss whether the circadian clock can be regulated by EC‐EET using the cyanobacterium Synechococcus elongatus PCC7942 as a model system. In vivo monitoring of chlorophyll fluorescence revealed that the redox state of the plastoquionone pool could be controlled with EC‐EET by simply changing the electrode potential. As a result, the endogenous circadian clock of S. elongatus cells was successfully entrained through periodically modulated EC‐EET by emulating the natural light/dark cycle, even under constant illumination conditions. This is the first example of regulating the biological clock by electrochemistry.     

单电子转移活性自由基聚合的现状及展望

重点介绍了单电子转移活性自由基聚合的机理及适合该聚合体系的催化剂、配体、溶剂种类和单体适用范围,并探讨了单电子转移活性自由基聚合的发展前景。     

基于海藻酸钠电沉积技术制备ZnO量子点及其复合膜的检测应用研究

天然高分子电沉积技术为构建新型功能材料和器件提供了契机.ZnO量子点(QDs)具备无毒、荧光稳定等特点日益受到人们的重视.本工作基于天然高分子海藻酸钠的配位电沉积技术制备ZnO QDs及其纳米复合膜;所采用方法具备操作简单、易于控制、条件温和、绿色环保等优点;并且产物后处理简便,可以直接在电极上构建出ZnO QDs/海...