Ionic miscibility enhancement via microion elimination in sulfonated polystyrene/poly(ethyl-acrylate-co-4-vinyl pyridine) ionomer blends

Miscibility enhancement of ionomer/ionomer and ionomer/polymeric acid systems is studied on the polymer pairs of poly(styrene-co-tetramethyl ammonium styrenesulfonate)/poly(ethyl acrylate-co-N-methyl-4-vinylpyridinium iodide) and poly(styrene-co-styrenesulfonic acid)/poly(ethyl acrylate-co-N-methyl-4-vinylpyridinium iodide). NMR and dynamic mechanical results show that in these blends direct macroion–macroion interaction can be achieved with the elimination of microcounterions from the polymer chains. Ion-ion attraction leads to a miscibility enhancement comparable to that of the previously reported proton transfer blends; a miscible blend is obtained with ca. 5 mol% of ions in the polymers.     

Novel triarylamine‐based alternating conjugated polymer with high hole mobility: Synthesis,electro‐optical,and electronic properties

Novel bi‐triphenylamine‐containing aromatic dibromide M3 , N,N‐bis(4‐bromophenyl)‐N′,N′‐dipheny‐l,4‐phenylenediamine, was successfully synthesized. The novel conjugated polymer P1 having number‐average molecular weight of 1.31 × 10⁴ was prepared via Suzuki coupling from the dibromide M3 and 9,9‐dioctylfluorene‐2,7‐diboronic acid bis(1,3‐propanediol) ester. Polymer P1 had excellent thermal stability associated with a high glass‐transition temperature (T_g = 141 °C). The hole‐transporting and UV‐vis‐near‐infrared electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the conjugated polymer films cast onto indium‐tin oxide‐coated glass substrates exhibited two reversible oxidation redox couples at E_1/2 values of 0.73 and 1.13 V versus Ag/Ag⁺ in acetonitrile solution. The hole mobility of the conjugated polymer P1 revealed ～10^?3 cm² V^?1 s^?1, which is much higher than that of other conjugated polymer systems. The observed UV‐vis‐near‐infrared absorption change in the conjugated polymer film P1 at applied potentials ranging from 0.00 to 1.23 V are fully reversible and associated with strong color changes from pale yellowish in its neutral form to green and blue in its oxidized form. Using a combination of experimental study and theoretical investigation, we proposed an oxidation mechanism based on molecular orbital theory, which explains the cyclic voltammetry experimental results well. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Inhibited oxidation of a polyethylene melt

The oxidation of linear polyethylene inhibited by an effective antioxidant of the phenolic type, viz. 2,2′-methylene-bis (4-methyl-6-tert. butylphenol), has been studied over the temperature range 170–210. There is a critical concentration of antioxidant above which the rate of its consumption is directly proportional to its concentration. Deviations from this dependence are due to chain initiation by direct oxidation of the polymer and to reactions involving the products derived from the antioxidant: these products can also retard the oxidation. Similar results have been obtained using the amine type antioxidant, N-phenyl-N′-cyclohexyl-p-phenylenediamine. Some features of the mechanism of polyolefin oxidation are discussed.     

Electrochemical characterization of small organic hole-transport molecules based on the triphenylamine unit

A series of substituted triphenylamine-containing organic compounds are synthesized and their hole-transport properties are examined by electrochemical and spectroelectrochemical methods. Several substituted tirphenylamines exhibited irreversible electron-transfer reactions both in the oxidative and reductive scan. On the other hand, the cyclic voltammograms of the p-phenylenediamine series are well defined. N,N^′-bis(4-nitrophenyl)-N,N^′-diphenyl-1,4-phenylenediamine (NPD) exhibited two reversible oxidation redox couples at +1.00 and +1.28 V vs. Ag/AgCl in dichloromethane solution. There is one reversible reduction redox couple at −1.12 V and one irreversible wave with E_p,c at −1.87 V. Cyano-substituted p-phenylenediamine (CPD) exhibited similar oxidation redox couples. Amino-substituted p-phenylenediamine (APD) is easier to oxidize than NPD and CPD. APD exhibits two reversible oxidation redox couples at +0.40 and +0.70 V and two extra irreversible oxidation waves at +1.26 and +1.52 V. Optically transparent thin-layer electrode (OTTLE) coupled with UV/Vis/NIR spectroscopy was used to examine the oxidation products of the above reactions. The electrogenerated cation and dication of the substituted p-phenylenediamine are very stable in the spectroelectrochemical studies. Oxidation of the compound APD exhibited a distinguished absorption pattern, which is different from those of compound NPD and compound CPD.     

Electroactive aromatic polyamides and polyimides with adamantylphenoxy-substituted triphenylamine units

A new triphenylamine-containing aromatic diamine monomer, 4-[4-(1-adamantyl)phenoxy]-4′,4″-diaminotriphenylamine, was synthesized from cesium fluoride-mediated N,N-diarylation of 4-(1-adamantyl)-4′-aminodiphenyl ether with 4-fluoronitrobenzene and subsequent reduction of the resultant dinitro compound. Novel electroactive aromatic polyamides and polyimides with adamantylphenoxy-substituted triphenylamine moieties were prepared from the newly synthesized diamine monomer with aromatic dicarboxylic acids and tetracarboxylic dianhydrides, respectively. All the resulting polymers were amorphous and most of them were readily soluble in polar solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) and could be solution-cast into transparent and strong films with good mechanical properties. These polymers exhibited glass-transition temperatures between 254 and 310 °C, and they were fairly stable up to a temperature above 450 °C for the polyamides and above 500 °C for the polyimides. These polymers exhibited strong UV-vis absorption maxima at 293-346 nm in solution, and the photoluminescence spectra of polyamides showed maximum bands around 408-452 nm in the blue region. Cyclic voltammograms of the polyamide and polyimide films on an indium-tin oxide (ITO)-coated glass substrate exhibited one pair of reversible redox couples at half-wave oxidation potentials (E_1/2) around 0.83-0.86 V and 1.12-1.13 V, respectively, versus Ag/AgCl in an acetonitrile solution. All the polymer films revealed good electrochemical and electrochromic stability by repeatedly switching electrode voltages between 0.0 V and 1.1-1.4 V, with coloration change from the pale yellowish neutral state to the green or blue oxidized state.     

The electrocatalytic reactions of adenine, guanine, H2O, H2O2, N2H4, and l -cysteine catalyzed by poly(Ni(4-TMPyP)) film-modified electrodes

Electrochemical preparation of poly(nickel tetrakis(N-methyl-4-pyridyl)porphyrin) tetratosylate (poly-Ni(4-TMPyP)) produces stable and electrochemically active films in strong and weak basic aqueous solutions. These films were produced on glassy carbon and gold electrodes. The electrochemical quartz crystal microbalance and cyclic voltammetry were used to study the in situ growth of poly(Ni(4-TMPyP)) films. The electrochemical properties of poly(Ni(4-TMPyP)) films indicate that the redox process was confined in to the immobilized film. The electrochemical quartz crystal microbalance results showed an ion exchange reaction for the redox couple. The polymer films showed one new redox couple when transferred to strong and weak basic aqueous solutions and the formal potential was found to be pH dependent. The electrocatalytic oxidation of H₂O by a nickel tetrakis(N-methyl-4-pyridyl)porphyrin film-modified electrode was also performed. The mechanism of oxygen evolution was determined by cyclic voltammetry, chronoamperometry and rotating ring disc electrode methods. The oxygen evolution was determined by a bicatalyst system using hemoglobin, and iron tetrakis (N-methyl-2-pyridyl)porphyrin as catalyst to detect the oxygen by electrocatalytic reduction. The electrocatalytic oxidations of adenine, guanine, H₂O₂, N₂H₄, NH₂OH, and l-cysteine by the film-modified electrode obtained from water-soluble nickel porphyrin were also investigated.     

Electrochemical and electrochromic properties of novel aromatic poly(amine-amide)s derived from N,N′-bis(4-carboxyphenyl)-N,N′-diphenyl-1,4-phenylenediamine

A series of novel triphenylamine-containing aromatic poly(amine-amide)s were prepared from the dicarboxylic acid, N,N′-bis(4-carboxyphenyl)-N,N′-diphenyl-1,4-phenylenediamine, and various diamines by direct phosphorylation polycondensation. All the poly(amine-amide)s were amorphous, soluble in a variety of organic solvents, and could be solution cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with relatively high glass-transition temperatures (195-280 °C). These polymers exhibited strong UV-Vis absorption bands at 330-346 nm and their photoluminescence showed maximum bands around 516-535 nm in NMP solution. The hole-transporting and electrochromic properties are examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine-amide)s prepared by casting polymer solution onto an indium-tin oxide (ITO)-coated glass substrate exhibited two reversible oxidative redox couples at potential 0.73-0.78 V and 1.12-1.18 V, respectively vs Ag/AgCl in acetonitrile solution. All the poly(amine-amide)s exhibited excellent reversibility of electrochromic characteristics by continuous ten cyclic scans between 0.0 and 1.40 V, with a color change from original pale yellowish neutral form to the green and then to blue oxidized forms.     

Highly stable electrochromic polyamides based on N,N‐bis(4‐aminophenyl)‐N′,N′‐bis(4‐tert‐butylphenyl)‐1,4‐phenylenediamine

A new triphenylamine‐containing aromatic diamine monomer, N,N‐bis(4‐aminophenyl)‐N′,N′‐bis(4‐tert‐butylphenyl)‐1,4‐phenylenediamine, was synthesized by an established synthetic procedure from readily available reagents. A novel family of electroactive polyamides with di‐tert‐butyl‐substituted N,N,N′,N′‐tetraphenyl‐1,4‐phenylenediamine units were prepared via the phosphorylation polyamidation reactions of the newly synthesized diamine monomer with various aromatic or aliphatic dicarboxylic acids. All the polymers were amorphous with good solubility in many organic solvents, such as N‐methyl‐2‐pyrrolidinone (NMP) and N,N‐dimethylacetamide, and could be solution‐cast into tough and flexible polymer films. The polyamides derived from aromatic dicarboxylic acids had useful levels of thermal stability, with glass‐transition temperatures of 269–296 °C, 10% weight‐loss temperatures in excess of 544 °C, and char yields at 800 °C in nitrogen higher than 62%. The dilute solutions of these polyamides in NMP exhibited strong absorption bands centered at 316–342 nm and photoluminescence maxima around 362–465 nm in the violet‐blue region. The polyamides derived from aliphatic dicarboxylic acids were optically transparent in the visible region and fluoresced with a higher quantum yield compared with those derived from aromatic dicarboxylic acids. The hole‐transporting and electrochromic properties were examined by electrochemical and spectro‐electrochemical methods. Cyclic voltammograms of the polyamide films cast onto an indium‐tin oxide‐coated glass substrate exhibited two reversible oxidation redox couples at 0.57–0.60 V and 0.95–0.98 V versus Ag/AgCl in acetonitrile solution. The polyamide films revealed excellent elcterochemical and electrochromic stability, with a color change from a colorless or pale yellowish neutral form to green and blue oxidized forms at applied potentials ranging from 0.0 to 1.2 V. These anodically coloring polymeric materials showed interesting electrochromic properties, such as high coloration efficiency (CE = 216 cm²/C for the green coloring) and high contrast ratio of optical transmittance change (ΔT%) up to 64% at 424 nm and 59% at 983 nm for the green coloration, and 90% at 778 nm for the blue coloration. The electroactivity of the polymer remains intact even after cycling 500 times between its neutral and fully oxidized states. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2330–2343, 2009     

Insulin release behavior of poly(N-isopropylacrylamide-co-N-vinyl-2-pyrrolidone) hydrogel based on modified melamine crosslinkers

Novel hydrogels based on poly(N-isopropylacrylamide-co-N-vinyl-2-pyrrolidone) (PNIPAAm/PNVP), were synthesized by solution radical polymerization using water as solvent and different weight percentage of crosslinkers ranging from 0.5 to 4%. The monomer mol ratios of NIPAAm/VP (0.9/0.1, 0.5/0.5, and 0.1/0.9) were used in all cases. N,N′-methylenebisacrylamide (MBA) and the new synthesized N,N,N-triacrylamido melamine (MAAm) were used as crosslinkers. The swelling parameters such as the swelling ratio Q, equilibrium water content (EWC), volume fraction of polymer φ_p and volume fraction at crosslinking φ_r were calculated from swelling measurements at different temperatures. The lower critical solution temperatures (LCST) of the prepared hydrogels were measured using DSC technique. The data of LCST indicated that the NIPAAm/VP crosslinked with MAAm or MBA showed reversible swelling and shrinking with temperature changes. The temperature dependence of swelling ratio and response kinetics upon heating or cooling was also investigated to understand the smart properties, i.e., temperature sensitive properties of these smart hydrogels. The in vitro release experiments were carried out at 22 and 37°C, respectively, to investigate the effect of temperature-sensitive property of these PNIPAAm/PNVP hydrogels crosslinked with MAAm and MBA crosslinkers on insulin release profiles.     

Thermal decomposition of anion-exchange resin based on copolymer of 4-vinylpyridine

Formal kinetic model is suggested on the basis of experimental studies of the heat-release kinetics in decomposition of an anion-exchange resin, copolymer of N-methyl-4-vinylpyridinium chloride and divinylbenzene. The model makes it possible to determine the service life of the resin in the temperature range 100–170°C in optimization of the process in which monosilane is synthesized from trichlorosilane with the resin used as a catalyst.     

Combined QCM-D/GE as a tool to characterize stimuli-responsive swelling of and protein adsorption on polymer brushes grafted onto 3D-nanostructures

A combined setup of quartz crystal microbalance and generalized ellipsometry can be used to comprehensively investigate complex functional coatings comprising stimuli-responsive polymer brushes and 3D nanostructures in a dynamic, noninvasive in situ measurement. While the quartz crystal microbalance detects the overall change in areal mass, for instance, during a swelling or adsorption process, the generalized ellipsometry data can be evaluated in terms of a layered model to distinguish between processes occurring within the intercolumnar space or on top of the anisotropic nanocolumns. Silicon films with anisotropic nanocolumnar morphology were prepared by the glancing angle deposition technique and further functionalized by grafting of poly-(acrylic acid) or poly-(N- isopropylacrylamide) chains. Investigations of the thermoresponsive swelling of the poly-(N-isopropylacrylamide) brush on the Si nanocolumns proved the successful preparation of a stimuli-responsive coating. Furthermore, the potential of these novel coatings in the field of biotechnology was explored by investigation of the adsorption of the model protein bovine serum albumin. Adsorption, retention, and desorption triggered by a change in the pH value is observed using poly-(acrylic acid) functionalized nanostructures, although generalized ellipsometry data revealed that this process occurs only on top of the nanostructures. Poly-(N-isopropylacrylamide) is found to render the nanostructures non-fouling properties.     

Enhanced redox stability and electrochromic properties of aromatic polyamides based on N,N‐bis(4‐carboxyphenyl)‐N′,N′‐bis(4‐tert‐butylphenyl)‐1,4‐phenylenediamine

A new bis(triphenylamine)‐type dicarboxylic acid monomer, N,N‐bis(4‐carboxyphenyl)‐N′,N′‐bis(4‐tert‐butylphenyl)‐1,4‐phenylenediamine, was prepared by a well‐established procedure and led to a new family of redox‐active aromatic polyamides with di‐tert‐butyl‐substituted N,N,N′,N′‐tetraphenylphenylenediamine (TPPA) segments. The resulting polyamides were amorphous with good solubility in many organic solvents, and most of them could be solution cast into flexible polymer films. The polyamides exhibited high thermal stability with glass‐transition temperatures in the range of 247–293 °C and 10% weight‐loss temperatures in excess of 500 °C. They showed well‐defined and reversible redox couples during oxidative scanning, with a strong color change from a colorless or pale yellowish neutral form to green and blue oxidized forms. They had enhanced redox stability and electrochromic performance when compared with the corresponding analogs without tert‐butyl substituents on the TPPA unit. The polyamide with TPPA units in both the diacid and diamine components shows multicolored electrochromic behavior. A polyamide containing both the cathodic coloring anthraquinone chromophore and the anodic coloring TPPA chromophore has the ability to show red, green, and blue states, toward single‐component RGB electrochromics. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and study of 3-methyl-6H-indolo[2,3-b]quinoxalines

By the condensation of isatin, N-methyl-, N-propyl-, N-benzoylisatin with 4-methyl-1,2-benzeneldiamine 3-methyl-6H-indolo[2,3-b]quinoxalines were obtained in high yields. The reaction occurs stereoselectively, in the mixture only one of possible isomers is present. By the oxidation of methyl group of the quinoxaline fragment new carbonyl derivatives were obtained, and by the reduction of nitro group, the corresponding indoloquinoxalinamines.     

Structure and properties of protonated N-alkyl-2-aza[3]ferrocenophanes

Protonation of N-alkyl-2-aza[3]ferrocenophanes by HCl and NH₄PF₆ affords hexafluorophosphate salts having a trialkylammonium group. Structures of the protonated and unprotonated N-(p-methylbezyl)-2-aza[3]ferrocenophanes were determined by X-ray crystallography. Variable temperature ¹³C{¹H} NMR spectra of the N-protonated N-hexyl-2-aza[3]ferrocenophane revealed inversion of the nitrogen of the 2-aza[3]ferrocenophane on the NMR time scale probably via partial deprotonation of the nitrogen atom. Cyclic voltammograms of the N-protonated compounds exhibited reversible redox peaks at higher potentials than those of the corresponding neutral ferrocenophanes.     

Electrochemical Properties of an Osmium(II) Copolymer Film and Its Electrocatalytic Ability Towards the Oxidation of Ascorbic Acid in Acidic and Neutral pH

Copolymerization of an osmium(II) functionalized pyrrole moiety, osmium‐bis‐N,N'‐(2,2′‐bipyridyl)‐N‐(pyridine‐4‐ylmethyl‐(8‐pyrrole‐1yl–octyl)‐amine)chloride ( I ) with 3‐methylthiophene was carried out. The resulting conducting polymer film exhibited a clear redox couple associated with the Os^3+/2+ response and the familiar conducting polymer backbone signature. The effect of film thickness upon the redox properties of the copolymer was investigated in organic electrolyte solutions. Scanning electron micrographs (SEM) along with energy dispersive X‐ray (EDX) spectra of the copolymerized films were undertaken, both after formation and redox cycling in neutral buffer solution. These clearly show that electrolyte is incorporated into the polymer film upon redox cycling through the Os^3+/2+ redox system. The Os^3+/2+ response associated with the copolymer was seen to be significantly altered in the presence of ascorbic acid both in acidic and neutral pH buffer solutions. This pointed to an electrocatalytic reaction between the ascorbic acid and the Os³⁺ form of the copolymer. Under acidic conditions the copolymer film exhibited a sensitivity of 1.76 (±0.05) μA/mM with a limit of detection (LOD) of 1.45 μM for ascorbic acid. Under neutral pH conditions the copolymer exhibited a sensitivity of 19.26 (±1.05) μA/mM with a limit of detection (LOD) of 1.28 μM for ascorbic acid.     

Preparation, characterization, and electrocatalytic properties of hybrid coatings of hexacyanometalate-doped-cationic films

Electrochemically active hybrid coatings based on cationic films, didodecyldimethylammonium bromide (DDAB), and poly(diallyldimethylammonium chloride) (PDDAC) are prepared on electrode surface by cycling the film-covered electrode repetitively in a pH 6.5 solution containing Fe(CN)₆ ³⁻ and Ru(CN)₆ ⁴⁻ anions. Modified electrodes exhibited stable and reversible voltammetric responses corresponding to characteristics of Fe(CN)₆ ^3−/4− and Ru(CN)₆ ^4−/3− redox couples. The cyclic voltammetric features of hybrid coatings resemble that of electron transfer process of surface-confined redox couple. Electrochemical quartz crystal microbalance results show that more amounts of electroactive anionic complexes partitioned into DDAB coating than those doped into PDDAC coating from the same doping solution. Peak potentials of hybrid film-bound redox couples showed a negative shift compared to those at bare electrode and this shift was more pronounced in the case of DDAB. Finally, the advantages of hybrid coatings in electrocatalysis are demonstrated with sulfur oxoanions.     

Autoinflammation et stabilité thermique de la poly(vinyl-4-pyridine) quaternisée—IV Methode d'étude des mécanismes d'autoinflammation. Application aux cas du bromure de poly(vinyl-4-pyridinium) et du bromure de poly(N(3-propionyl)4-vinylpyridinium)

We have determined the nature of the combustible gas produced from oxidizing pyrolysis of a polymer (the bromide of poly(vinyl-4-pyridinium) and the bromide of poly(N(3-propionyl)4-vinylpyridinium)). The pyrolysis temperature chosen was just below the self ignition temperature and the pyrolysis was performed in air at atmospheric pressure. We analysed the gaseous products by gas chromatography and mass spectrometry. We found a correlation between the change of the self ignition temperature, the change of the composition of the gas phase and the change of the percentage of residue. We assumed that the gas mixture originates the self ignition of the polymer. The composition of the gas mixture depends on the composition of the polymer.     

trans-4-Hydroxy-l-proline: a novel starting material for N-alkylpyrroles synthesis

The reaction of aldehydes with trans-4-hydroxy-l-proline was studied for the first time, resulting in the formation of N-alkylpyrroles in good to excellent yields, via decarboxylation followed by redox isomerization under neutral conditions. The neutral conditions allow access to efficient synthesis of N-alkyl pyrroles with high functional group tolerance.     

Open tubular capillary electrochromatography with block co-polymer coating for separation of β-lactam antibiotics

Unique block co-polymer P(MAn-St-NIPAm) has been successfully synthesized by reversible addition fragmentation chain transfer radical polymerization protocol. Based on the tunable hydrophobic/hydrophilic properties of the block co-polymer, a new open tubular capillary electrochromatography (OT-CEC) system has been constructed with the prepared block co-polymer as the coating and applied in analysis of β-lactam antibiotics in serum samples.     

Nickel(II) Complex of N4 Schiff Base Ligand as a Building Block for a Conducting Metallopolymer with Multiple Redox States

Metal–ligand interactions in monomeric and polymeric transition metal complexes of Schiff base ligands largely define their functional properties and perspective applications. In this study, redox behavior of a nickel(II) N₄-anilinosalen complex, [NiAmben] (where H₂Amben = N,N′-bis(o-aminobenzylidene)ethylenediamine) was studied by cyclic voltammetry in solvents of different Lewis basicity. A poly-[NiAmben] film electrochemically synthesized from a 1,2-dichloroethane-based electrolyte was investigated by a combination of cyclic voltammetry, electrochemical quartz crystal microbalance, in situ UV-Vis spectroelectrochemistry, and in situ conductance measurements between −0.9 and 1.3 V vs. Ag/Ag⁺. The polymer displayed multistep redox processes involving reversible transfer of the total of ca. 1.6 electrons per repeat unit, electrical conductivity over a wide potential range, and multiple color changes in correlation with electrochemical processes. Performance advantages of poly-[NiAmben] over its nickel(II) N₂O₂ Schiff base analogue were identified and related to the increased number of accessible redox states in the polymer due to the higher extent of electronic communication between metal ions and ligand segments in the nickel(II) N₄-anilinosalen system. The obtained results suggest that electrosynthesized poly-[NiAmben] films may be viable candidates for energy storage and saving applications.