Synthesis and characterization of fully disulfonated poly(arylenethioethersulfone)s containing hexafluoroisopropylidene moiety

High molecular weight sulfonated poly(arylenethioethersulfone) homopolymer containing hexafluoroisopropylidene moiety (6F-SPTES-100) was synthesized from the monomers 3, 3′-disulfonated-4, 4′-difluorodiphenylsulfone and 4, 4′-(hexafluoroisopropylidene) diphenylthiol, using 4-fluorobenzophenone as the end-capping agent in polar aprotic solvents at temperatures up to 180 °C to provide the desired polymeric composition for utilization as proton exchange membrane (PEM) in fuel cells applications. Tough, ductile freestanding membranes were fabricated from N, N-dimethylacetamide (DMAc) by solvent-casting. The end-capped 6F-SPTES-100 polymer was fully characterized and the membrane was found to have proton conductivity as high as 180 mS/cm which was measured at 85 °C and 65% relative humidity. The proton conductivity of 6F-SPTES-100 was approximately two and half times higher than that of Nafion-117 under comparable conditions. The swelling and solubility characteristics of the 6F-SPTES-100 polymer in water are directly related to the high degree of sulfonation of the polymer backbone.     

Studies on anhydrous proton conducting membranes based on imidazole derivatives and sulfonated polyimide

Anhydrous proton conducting membranes based on sulfonated polyimide (sPI) and imidazole derivatives were prepared. The acid-base composite membranes show a good chemical oxidation stability and high thermal stability. The addition of imidazole derivatives in sPIs can improve the chemical oxidation stability of the composite membranes enormously, and even much better than that of pure sPI. The proton conductivity of a typical sPI/xUI(2-undecylimidazole) composite membrane can reach 10⁻³ S cm⁻¹ at 180 °C under the anhydrous condition. The proton conductivity of the acid-base composite membranes increases significantly with increasing content of UI. Moreover, UI in sPI/xUI composite membrane is difficult to be brought out by the vapor due to the existence of long hydrophobic moiety, which will improve the stability and lifetime of the membranes in the fuel cells.     

A novel donor-acceptor polymeric electrochromic material containing carbazole and 1,8-naphtalimide as subunit

We report here the synthesis of a novel polymeric electrochromic material containing carbazole (Cbz)-donor and 1,8-napthalimide-acceptor as subunit. The band gap E_g was measured using UV-vis spectroscopy and compared with that obtained by cyclic voltammetry (CV). Due to intramolecular electron transfer from Cbz-donor to 1,8-napthalimide-acceptor, the fluorescence quenching was observed. When the spectro-electrochemical and electrochromic properties of polymer film were investigated, various tones of green color were obtained on the polymeric film. In the positive regime, the polymer film obtained thereby is dark green resulting from the association of carbazolylium cation radicals at oxidized state and then it can be bleached by electrochemical reduction. Besides, in the negative regime, yellowish green color of film converted to blue attributed to reduction of the 1,8-napthalimide moiety. Finally, the polymeric electrochromic exhibits multi-electrochromic behavior, high redox stability, high coloration efficiency and reasonable response time.     

A novel coumarin‐based fluorescent probe for selective detection of cysteine over homocysteine

A coumarin‐based fluorescent probe containing both acrylate moiety and an allyl substituent was developed for distinguishing cysteine from homocysteine. The maximum absorption wavelength of the probe showed a bathochromic shift upon addition of cysteine and the colour changed from colourless to yellow. The maximum fluorescence emission at 462 nm of the probe was dramatically enhanced upon addition of cysteine in aqueous solution. In HEPES buffer (pH = 7.4, EtOH/H₂O = 9:1, v/v), both of the fluorescence emission bands of the probe at ca. 390 and 462 nm were intensely enhanced upon the addition of cysteine, while other amino acids, namely, homocysteine, asparaginic acid, methionine, glycine, phenylalaninase, valine, tryptophan, serine, glutamic acid and glutathione, did not cause a remarkable change. The probe can be used for selectively colorimetric and ratiometric fluorescent detection of cysteine over homocysteine and other common amino acids in both organic media and aqueous solution. The concentration of cysteine can be estimated by titration of the probe in aqueous solution, and the detection limit of the probe towards cysteine was 2 μmol/L.     

Utilization of plant ash for the fabrication of novel superabsorbent composites with potassium‐release characteristics

Design and synthesis of the agricultural and ecological superabsorbent materials with cost‐efficient and fertilizer‐release characteristics has recently attracted considerable interests. In this work, the novel poly(sodium‐potassium acrylate‐co‐acrylamide)/plant ash (PNa‐KA‐co‐AM/PA) superabsorbent composites with potassium‐release characteristics were prepared using partially neutralized acrylic acid (Na‐KA), acrylamide (AM), and plant ash (PA) as raw materials, ammonium persulfate (APS) as the initiator, and N,N′‐methylenebisacrylamide (MBA) as the crosslinker. The structure, morphologies, and thermal stability of the composites were characterized by Fourier transform infrared spectrophotometer, scanning electron microscopy, and TGA techniques, respectively. The effects of MBA concentration and PA content on water absorbency were studied, and the swelling properties of the composites in saline solutions and various pHs solution as well as their potassium‐release capabilities were also evaluated. Results indicate that the composites exhibit better thermal stability, salt‐resistant performance, pH‐stability, and potassium‐release properties, and can act as a fertilizer and an effective water‐saving material for agricultural and ecological application. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and properties of photoluminescent copolymer containing 1,3,4‐oxadiazole and carbazole rings

The luminescent copolymer 2‐phenyl‐5‐[3′‐(methacrylamido)phenyl]‐1,3,4‐oxadiazole and vinylcarbazole (PMAPO–VCZ), combining hole‐facilitating moiety, carbazole ring, and electron‐facilitating moiety, 1,3,4‐oxadiazole, as side groups, was synthesized by a radical polymerization of the olefinic monomer PMAPO and VCZ. For comparison, the homopolymer P‐PMAPO was also synthesized by similar procedures. The solubility, thermal, and optical properties of the copolymers were investigated. The synthesized copolymer was soluble in common organic solvents but the homopolymer of PMAPO was dissolved only by hot THF. Thermogravimetric analysis and differential scanning calorimetry measurements showed that the copolymer and homopolymer exhibit good thermal stability up to 360 and 340°C with glass‐transition temperatures higher than 105 and 65°C, respectively. The photoluminescence properties were investigated. The results showed that the copolymer emits blue and blue‐green light and the emission spectra of monomer and polymers exhibit obvious solvent effect. With the increase of polarity of solvents, the fluorescence spectra distinctly change, appearing with a red shift at room temperature. The concentration‐dependent emission spectra change significantly with the increase of concentration. In addition, when N,N‐dimethylaniline (DMA) was gradually added to the solution of copolymers, the emission intensity of fluorescence was dramatically increased. However, when the concentration of DMA was increased beyond a certain level, the emission intensity of fluorescence gradually decreased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2777–2783, 2004     

Properties of Didecyldimethylammonium Formate and Sodium Fatty Alcohol Ether Carboxylate Mixed Systems

The surface activities and application properties of didecyldimethylammonium formate (DDAF) and sodium fatty alcohol ether carboxylate (AEC-9Na) mixed systems were measured. The results showed that the critical micelle concentration and surface tension of mixed systems have lower values than that of a single surfactant solution, which is attributed to the synergism of DDAF and AEC-9Na. It was found that the emulsifying properties for kerosene and wetting properties of the mixed systems were also better than single component surfactants. In addition, the mixed systems of AEC-9Na (16 wt%) with DDAF showed both better detergency and excellent antibacterial properties.     

Preparation,characterization, and flocculation performance of P(acrylamide‐co‐diallyldimethylammonium chloride) by UV‐initiated template polymerization

This study prepared TPDA, a high‐intrinsic‐viscosity cationic polyacrylamide, through ultraviolet (UV)‐initiated template polymerization. Acrylamide (AM) and diallyldimethylammonium chloride (DMD) served as monomers, and poly sodium polyacrylate (PAAS) served as the template. The structure of TPDA was characterized by Fourier‐transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. The synthetic conditions of TPDA were studied and optimized by single‐factor experiments. An optimized product was obtained at an intrinsic viscosity of 11.3 dL g^?1 and a conversion rate of 97.2% with a total monomer concentration of 20%, DMD concentration of 30%, initiator concentration of 0.045%, pH of 8, EDTA concentration of 0.3%, and UV irradiation of 90 min. Results showed that TPDA was the copolymer of AM and DMD with a micro‐block structure at the molecular chain. Given its high intrinsic viscosity and cationic block structure, TPDA performed better in kaolin flocculation than that prepared without template addition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41747.     

Effect of montmorillonite on properties of styrene–butadiene–styrene copolymer modified bitumen

Clay/styrene–butadiene–styrene (SBS) modified bitumen composites were prepared by melt blending with different contents of sodium montmorillonite (Na‐MMT) and organophilic montmorillonite (OMMT). The structures of clay/SBS modified bitumen composites were characterized by XRD. The XRD results showed that Na‐MMT/SBS modified bitumen composites may form an intercalated structure, whereas the OMMT/SBS modified bitumen composites may form an exfoliated structure. Effects of MMT on physical properties, dynamic rheological behaviors, and aging properties of SBS modified bitumen were investigated. The addition of Na‐MMT and OMMT increases both the softening point and viscosity of SBS modified bitumens and the clay/SBS modified bitumens exhibited higher complex modulus, lower phase angle. The high‐temperature storage stability can also be improved by clay with a proper amount added. Furthermore, clay/SBS modified bitumen composites showed better resistance to aging than SBS modified bitumen, which was ascribed to barrier of the intercalated or exfoliated structure to oxygen, reducing efficiently the oxidation of bitumen, and the degradation of SBS. POLYM. ENG. SCI., 47:1289–1295, 2007. © 2007 Society of Plastics Engineers     

Synthesis and fluorescence properties of a waterborne polyurethane–acrylic hybrid polymeric dye

A waterborne polyurethane–acrylic hybrid polymeric dye was prepared depending on soap-free emulsion polymerization method. The resulting polymeric dye composed of methyl methacrylate (MMA) monomer which was polymerized into polymethyl methacrylate (PMMA) as cores and waterborne polyurethane-based dye was synthesized by anchoring dye monomers (6-amino-2-cyclohexyl-benz[de]isoquinone-1,3-dione) to polyurethane chains as shells. The average particle sizes of the hybrid polymeric dye emulsions were found to be increased with the increase in MMA contents for MMA monomers. Compared with dye monomers, the absorption intensities and fluorescence intensities of the hybrid polymeric dye were enhanced with the increase of particle sizes. This study revealed that enhanced fluorescence intensity of the hybrid polymeric dye was mainly attributed to the hindered formation of exciplexes among dye monomers and an augmented light absorption area. It was found that the fluorescence intensity of the hybrid polymeric dye was increased with increasing temperature and the trend first increased and then decreased with increase in concentration. Furthermore, the fluorescence of the hybrid polymeric dye emulsions was found to be very stable and not sensitive to the fluorescence quencher.     

Synthesis and fluorescence properties of star‐shaped polymers carrying two fluorescent moieties

A well‐defined fluorescent star‐shaped polymer containing two different fluorescent functionalities one in the main chain and another in the end group was designed and synthesized by combining atom transfer radical polymerization (ATRP) and azide‐alkyne click reaction. The star polymer with four arms was prepared from copolymerization of methyl methacrylate and 4‐(2‐(9‐anthryl))‐vinyl‐styrene using ATRP. Subsequently the end group was modified with another fluorescent moiety by click coupling. The structure of all the intermediate and final products was established through NMR spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, UV?visible spectroscopy and fluorescence spectroscopy. The novel hybrid polymer exhibits an attractive high fluorescence at 494 nm and over a broad range which was a combination of both the fluorescence moieties. © 2013 Society of Chemical Industry     

Synthesis and fluorescence properties of novel benzoxazole‐ and chromone‐functionalised bis(arylvinylene)imidazoles

Novel benzoxazole‐ and chromone‐functionalised bis(arylvinylene)imidazoles were synthesised and characterised by proton nuclear magnetic resonance, Fourier Transform–infrared, mass spectrometry and elemental analyses. These dyes were found to exhibit two quite different types of fluorescence behaviour in the alkali examined; i.e. fluorescence quenching for the benzoxazole–imidazole hybrids and fluorescence enhancement for the chromone–imidazole hybrids. The benzoxazole‐based imidazoles emit intense green fluorescence, but the fluorescence is remarkably quenched upon addition of alkali. Such a process can be reversibly controlled by simple deprotonation/protonation of the imidazole group; thus, they exhibit efficient fluorescence on/off switchable behaviour. In contrast, significant fluorescence enhancement is observed for the chromone–imidazole hybrids in the presence of alkali. Without alkali, these imidazole dyes are very weakly fluorescent, whereas the addition of alkali leads to an appearance of strong blue fluorescence and a dramatic increase of emission intensity.     

Synthesis and performance of phenolic polybutadiene‐bound stabilizers

An antioxidant derivative, 6‐sulfanylhexyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propanoate, was synthesized and examined. With a radical initiator, the addition of this compound to pending vinyls of OH‐telechelic, low molecular weight liquid polybutadiene (LBH) was performed to various degrees of conversion to form polymeric antioxidants (PAOs) in which the phenolic moiety was separated from the main chain by a spacer [? CH₂CH₂? S? (CH₂)₆? O? CO? ]. Pure, unstabilized LBH was mixed in several ratios with PAOs, Irganox 1520, and Irganox 1076, and the oxidation stabilities of these mixtures, determined by thermogravimetric analysis and differential scanning calorimetry, were compared. Probably because of their good compatibility with LBH, PAOs exhibited equal or better effectiveness than commercial antioxidants of the Irganox type. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 885–889, 2003     

Molecular simulation of the glass transition and proton conductivity of 2,2′‐benzidinedisulfonic acid and 4,4′‐diaminodiphenylether‐2,2′‐disulfonic acid‐based copolyimides as polyelectrolytes for fuel cell applications

The glass transition temperatures (T_gs) and proton conductivities of polyimides synthesized from naphthalene‐1,4,5,8‐tetracarboxylic dianhydride (NTDA), 2,2′‐benzidinedisulfonic acid (BDSA), 4,4′‐diaminodiphenylether‐2,2′‐disulfonic acid (ODADS), and non‐sulfonated diamine monomers have been predicted using molecular dynamics simulations. The specific volumes for two dry and four hydrated NTDA‐based polyimides were plotted versus temperatures above and below T_gs to obtain the glass transition temperatures. The simulation results suggest that the ODADS‐based polyimide membranes exhibit lower T_gs and thus better mechanical properties than the BDSA‐based polyimides, which may be attributed to the high mobility of backbones of ODADS as supported by the vectorial autocorrelation function (VACF) results of this study. In addition, comparison of the simulated T_gs for the dry and hydrated ODADS‐based polyimides has shown that water content in polyimides can affect their T_gs. The proton conductivities of a representative polyimide in both dry and hydrated conditions have been obtained from molecular dynamics simulations of the proton and hydronium ion diffusion. The simulated conductivity for the hydrated NTDA‐ODADS/BAPB cell is in reasonable agreement with the experimental value obtained from the AC impedance method. The relationship between the chemical composition, chain flexibility, and the glass transition and proton conduction of these NTDA‐based polyimides was explored on the basis of VACF and pair correlation function analysis. Copyright © 2006 Society of Chemical Industry     

Sugar-dependent solubility and fluorescence property of copolymers consisting of phenylboronic acid and 2-hydroxyethyl methacrylate moieties

Copolymers consisting of N-3-acrylamidophenylboronic acid (APBA) and 2-hydroxyethyl methacrylate moieties (HEMA) were synthesized and their solubility and fluorescence properties were evaluated in the presence of sugar. The APBA–HEMA copolymer composed of 25 mol% of APBA moiety was found to be poorly soluble in water at pH 7.4. However, the water solubility of APBA–HEMA was improved in the presence of fructose in solution. The solubility of APBA–HEMA was influenced by fructose in a concentration-dependent manner, due to the formation of boronate ester of APBA moiety with fructose added. In addition, APBA–HEMA was modified with fluorescein isothiocyanate (FITC) for the fluorometric detection of sugars. The fluorescence intensity of FITC-modified APBA–HEMA was dependent on the type and concentration of sugars in solution. The fluorescence intensity of FITC-modified APBA–HEMA was highly enhanced by the addition of fructose, while the fluorescent response was negligibly small when other sugars were added. Thus, usefulness of FITC-modified APBA–HEMA for the selective determination of fructose was demonstrated.     

Monovalent ion dependence of neomycin B binding to an RNA aptamer characterized by spectroscopic methods

Understanding the interactions of small molecules like antibiotics with RNA is a prerequisite for the development of novel drugs. In this study we address structural and thermodynamic features of such interactions by using a simple model system: the binding of the highly charged antibiotic neomycin B to a short hairpin RNA molecule. Nucleotide A16, which acts as a flap over the neomycin B binding pocket, was substituted by the fluorescent adenine analogue 2-aminopurine (2-AP). Steady-state and time-resolved fluorescence measurements were complemented by UV-melting and circular dichroism studies. The binding of neomycin B at three sites was found to have a strong inverse correlation with Na(+) concentration. For the highest-affinity site, both fluorescence and UV absorption experiments were consistent with a model assuming at least three neomycin NH(3) (+) groups participating in addition to hydrogen bonds in electrostatic interactions with the RNA. The variation of fluorescence intensity and lifetime upon neomycin B binding indicated unstacking of 2-AP16 from neighbouring bases as it flipped over the binding pocket. RNA conformational changes upon binding of the antibiotic were confirmed by circular dichroism. The two weaker binding sites were characterized as unspecific binding to the aptamer, while the high-affinity binding event was shown to be highly specific even at high ionic concentration. In addition, 2-AP was confirmed to be a noninvasive fluorescent probe; it serves as a sensitive spectroscopic tool to investigate details of the interactions between small molecules and RNA.     

CMC and dynamic properties of poly(VA-<Emphasis Type="Italic">b</Emphasis>-St) copolymer micelles for drug delivery

The polymeric micelles from amphiphilic block copolymer poly(vinyl alcohol-b-styrene) (poly(VA-b-St)) with different syndiotacticity of poly(vinyl alcohol) (PVA) block were prepared by dialysis against water. Critical micelle concentration (CMC) and dynamic properties of poly(VA-b-St) copolymeric micelles were investigated by fluorescence techniques. From the fluorescence emission spectrum measurements using pyrene as a fluorescence probe, the observed CMC value was in the range of 0.125–4.47 mg/L. The CMC value increased with decreasing the weight ratio of PS to PVA block and with increasing the syndiotacticity of PVA block. The rate of pyrene release was very slow for block copolymers containing PVA block with higher syndiotacticity, which indicates that their micelles have increased kinetic stability. This work was presented at 13 ^th YABEC symposium held at Seoul, Korea, October 20–22, 2007.     

Die wirkungsweise der viskositätsindex-verbesserer

One of the major reasons for using polymeric additives is to obtain a product which has better viscosity-temperature characteristics than a comparable pure mineral oil. Extensive measurements of the viscosity-temperature behaviour of motor oils with and without polymer addition show the necessity of a revision of the generally accepted concept of the mechanism of viscosity index improvement. By addition of polymer the better viscosity-temperature characteristics of light oils, which are however of very limited value for lubrication of engines because of their low viscosity at high temperatures, can be maintained partially in the range of higher viscosities. So it becomes obvious how it is possible to produce multigrade oils both from polymers the polymer coil dimensions of which expand, as well as from polymers, the polymer coils of which contract with increasing temperature. In fact, coil expansion promotes viscosity index improvement to some extent but in no way does this effect play a decisive part.     

Influence of Hydrogen Bonding on Low Critical Micellar Concentration Value and Formation of Giant Vesicle of Triazole-Contained Amphiphile

An amphiphile molecule consisting of triazole moiety has been thoroughly investigated using different approaches in its aqueous condition. The studies have discovered the explicit function of its heteroaromatic ability in molecular self-assembling. From the fluorescence evidence, the triazole-based amphiphile has shown that the aggregation-induced emission behavior is mainly due to the triazolyl. It suggests that the triazole is directly involved in the self-assembling mechanism through an intermolecular interaction. This interaction can be verified by the shifting of proton frequency of the triazole, which is clearly shown by the constant frequency of the proton above the critical micellar concentration (CMC) value. The frequency suggests the establishing hydrogen bond that occurred between the hydrogen and the second nitrogen of the adjacent triazole. These results are consistent with the micellization of the molecule which was determined at a very low CMC value (0.1 mM). The absorbance and optical polarizing microscopy results also support the evidence of the growth of giant vesicles produced from the neutralization of the amphiphile. The formation of stable giant vesicles at neutral pH demonstrates the immediate strong hydrogen bonding connections within the triazoles layer in the bilayer. The discovery reveals that internal hydrogen bonds formed from a heteroaromatic with the appropriate molecular arrangement can promote self-aggregation and enhance overall stability.     

Time-dependent properties of bimodal POM — Application in powder injection molding

Powder Injection Molding is applied for manufacturing complex and precise components from metal, ceramics or cemented carbide powder. It basically consists of mixing the powder and a polymeric binder, injecting this mixture in a mold with the desired form, debinding and then sintering. Among the debinding techniques applied, catalytic debinding of polyoxymethylene (POM) stands out due to the high debinding rates and low risk of cracking. In this work, the potential use of a bimodal POM-based material as the main binder component was evaluated by comparing its thermal and time-dependent properties to a standard monomodal POM. In addition, the potential optimization of this bimodal material was investigated by preparing five new formulations of bimodal POM with higher concentration of short polymeric chains (wax). This work has shown that macroscopic properties of POM are sensitive to the addition of these short chains. For instance, the magnitude of the complex viscosity for the commercial bimodal material was found to be more than 67% lower than for the monomodal POM in the whole range of frequencies studied. Finally, a new formulation of bimodal POM was suggested with 8% of added wax concentration (in weight), resulting in a material with very fine structure that has shown even better flowability than the commercial bimodal POM, without compromising its thermal and mechanical properties.