THE USE OF CHEMICALLY MODIFIED ELECTRODES FOR LIQUID-CHROMATOGRAPHY AND FLOW-INJECTION ANALYSIS

The use of chemically modified electrodes (CMEs) for liquid chromatography and flow-injection analysis is reviewed. Electrochemical detection with CMEs based on electrocatalysis, permselectivity, ion flow in redox films, and ion transfer across the water-solidified nitrobenzene interface is discussed in terms of improving the stability, selectivity, and scope of electrochemical detectors, and the detection of electroinactive substances. More than 90 references are included.

Synthesis and properties of sulfonated poly[bis(benzimidazobenzisoquinolinones)] as hydrolytically and thermooxidatively stable proton conducting ionomers

Novel sulfonated poly [bis(benzimidazobenzisoquinolinones)] as hydrolytically and thermooxidatively stable electrolyte for high -temperature fuel cell applications are reported. A series of sulfonated polymers (SPBIBI-x, x refers to molar percentage of sulfonated dianhydride monomer) were synthesized from 6,6'-disulfonic-4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (SBTDA), 4,4-binaphthyl-1,1,8,8-tetracarboxylic dianhydride (BTDA), and 3,3'-diaminobenzidine. The chemical structures of those polymers as well as model compounds synthesized from SBTDA and o-phenylenediamine were confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR).

Novel Sulfonated Polyimide Ionomers by Incorporating Pyridine Functional Group in the Polymer Backbone

A series of sulfonated polyimides (SPIs) containing pyridine ring in the polymer backbone were synthesized by the polycondensation of 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTDA), 5-(2,6-bis(4-arninophenyl)pyridin-4-yl)-2-methoxy benzene sulfonic acid (SDAM), and 4,4'-diaminodiphenyl ether (ODA). Flexible, transparent, and tough membranes were obtained. Property study revealed that all the membranes displayed high thermal stability with the desulfonation and decomposition temperature higher than 290 and 540 degrees C, respectively, as well as good mechanical property with Young's modulus larger than 1.0 GPa, maximum strength (MS) on a scale of 60-80 MPa, and elongation at break (EB) ranged from 41.79 to 75.17%.

Synthesis of Soluble Poly(arylene ether sulfone) Ionomers with Pendant Quaternary Ammonium Groups for Anion Exchange Membranes

A new bisphenol monomer, 2,2'-dimethylaminemetllylene-4,4'-biphenol (DABP), was easily prepared by Mannich reaction of dimethylamine and formaldehyde with 4,4'-biphenol. Novel partially fluorinated poly(arylene ether sulfone)s with pendant quaternary ammonium groups were prepared by copolymerization of DABP, 4,4'-biphenol, and 3,3',4,4'- tetrafluorodiphenylsulfone, followed by reaction with iodomethane. The resulting copolymers PSQNI-x (where x represents the molar fraction of DABP in the feed) with high molecular weight exhibited outstanding solubility in polar aprotic solvents; thus, the flexible and tough membranes of PSQNI-x with varying ionic content could be prepared by casting from the DMAc solution. Novel anion exchange membranes, PSQNOH-x, were obtained by an anion exchange of PSQNI-x with 1 N NaOH.

Synthesis and properties of water stable poly[bis(benzimidazobenzisoquinolinone)] ionomers for proton exchange membranes fuel cells

A novel sulfonated tetraamine, di(triethylammonium)-4,4'-bis(3,4-diaminophenoxy)biphenyl-3,3'-disulfonate (BAPBDS), was successfully synthesized by nucleophilic aromatic substitution of 4,4'-dihydroxybiphenyl with 5-chloro-2-nitroaniline, followed by sulfonation and reduction. A high-temperature polycondensation of sulfonated tetraamine, non-sulfonated tetraamine (4,4 -bis(3,4-aminophenoxy)biphenyl) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (a) or 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianydride (b) gave the poly[bis(benzimidazobenzisoquinolinones)] ionomers SPBIBI-a(x) or SPBIBI-b(x), where x refers to the molar percentage of the sulfonated tetraamine monomer. Flexible and tough membranes of high mechanical strength were obtained by solution casting and the electrolyte properties of the polymers were intensively investigated. The ionomer membranes displayed excellent dimensional and hydrolytic stabilities.

Compatibilization of side-chain, thermotropic, liquid-crystalline ionomers to blends of polyamide-1010 and polypropylene

A novel side-chain, liquid-crystalline ionomer (SLCI) with a poly(methyl hydrosiloxane) main chain and side chains containing sulfonic acid groups was used in blends of polyamide-1010 (PA1010) and polypropylene (PP) as a compatibilizer. The morphological structure, thermal behavior, and liquid-crystalline properties of the blends were investigated by Fourier transform infrared, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscopy. The morphological structure of the interface of the blends containing SLCI was improved with respect to the blend without SLCI. The compatibilization effect of greater than 8 wt % SLCI for the two phases, PA1010 and PP, was better than the effects of other SLCI contents in the blends.

Dynamic mechanical studies of the sulfonated butyl rubber ionomers and their blends

Dynamic mechanical properties of sulfonated butyl rubber ionomers neutralized with different amine or metallic ion (zinc or barium) and their blends with polypropylene (PP), high-density polyethylene (HDPE), or styrene-butadiene-styrene (SBS) triblock copolymer were studied using viscoelastometry. The results showed that glass transition temperatures of ion pair-containing matrix and ionic domains (T-g1 and T-g2, respectively) of amine-neutralized ionomers were lower than those of ionomers neutralized with metallic ions, and the temperature range of the rubbery plateau on the storage modulus plot for amine-neutralized ionomers was narrower. The modulus of the rubbery plateau for amine-neutralized ionomers was lower than that of ionomers neutralized with zinc or barium ion. With increasing size of the amine, the temperature range for the rubbery plateau decreased, and the height of the loss peak at higher temperature increased. Dynamic mechanical properties of blends of the zinc ionomer with PP or HDPE showed that, with decreasing ionomer content, the T-m of PP or HDPE increased and T-g1 decreased, whereas T-g2 or the upper loss peak temperature changed only slightly. The T-g1 for the blend with SBS also decreased with decreasing ionomer content. The decrease of T-g1 is attributed to the enhanced compatibilization of the matrix of the ionomer-containing ion pairs with amorphous regions of PP or HDPE or the continuous phase of SBS due to the formation of thermoplastic interpenetrating polymer networks by ionic domains and crystalline or glassy domains.

Study on a series of main-chain liquid-crystalline ionomers containing sulfonate groups

A series of main-chain Liquid-crystalline ionomers containing sulfonate groups pendant on the polymer backbone were synthesized by an interfacial condensation reaction of 4,4'-dihydroxy-alpha,alpha'-dimethyl benzalazine, a mesogenic monomer, with brilliant yellow (BY), a sulfonate-containing monomer, and a 1/9 mixture of terephthaloyl and sebacoyl dichloride. The structures of the polymers were characterized by LR and UV spectroscopies. DSC and thermogravimetric analysis were used to measure the thermal properties of those polymers, and the mesogenic properties were characterized by a polarized optical microscope, DSC, and wide-angle X-ray diffraction. The ionomers were thermally stable to about 310 degreesC. They were thermotropic liquid-crystalline polymers (LCPs) with high mesomorphic-phase transition temperatures and exhibited broad nematic mesogenic regions of 160-170 degreesC, and they were lyotropic LCPs with willowy leaf-shaped textures in sulfuric acid. However, the thermotropic liquid-crystalline properties were somewhat weakened because the concentration of BY was more than 8%. The inherent viscosity in N-methyl-2-pyrrolidone suggested that intramolecular associations of sulfonate groups occurred at low concentration, and intermolecular associations predominated at higher concentration. (C) 2001 John Wiley & Sons, Inc.

Synthesis and characterization of chiral smectic side-chain liquid crystalline polysiloxanes and ionomers containing sulfonic acid groups

The synthesis of new chiral smectic A (S-A) side-chain liquid crystalline polysiloxanes (LCPs) and ionomers (LCIs) containing 4-allyloxy-benzoyl-4-(S-2-ethylhexanoyl) p-benzenediol his ate (ABB) as mesogenic units and 4-[[4-(2-propenyloxy)phenyl] azo]benzensulfonic acid (AABS) as nonmesogenic units is presented. The chemical structures of the monomers and polymers are confirmed by FTIR spectroscopy or H-1-NMR. Differential scanning calorimetry (DSC), optical polarizing microscopy, and X-ray diffraction measurements reveal that all the polymers P-I-P-IV and ionomers P-V-P-VI exhibit S-A texture. The results seem to demonstrate that the tendency toward the S-A-phase region increases with increasing sulfonic acid concentration, and the thermal stability of the S-A phase is determined by the flexibility of the polymer backbones and the interactions of sulfonic acid groups. (C) 2001 John Wiley & Sons, Inc.

Cation selectivity of perfluorosulfonate polymer

Selectivity coefficient measurement has been performed for K+,Ni2+,Fe3+ with Nafion 117 perfluorosulfonate polymer as-received forms. The results show that a linear Nernst response is exhibited for H+,K+,Pb2+,Ni2+,Co2+,Fe3+, and the ion selectivity coefficient of Nafion membrane for KC is better than Ni2+ and Fe3+.

Synthesis and Characterisation of Thermoplastic Ionomers based on Natural Rubber

Chemically modified novel thermo-reversible zinc sulphonated ionomers based on natural rubber (NR), radiation induced styrene grafted natural rubber (RI-SGNR), and chemically induced styrene grafted natural rubber (CI-SGNR) were synthesized using acetyl sulphate/zinc acetate reagent system. Evidence for the attachment of sulphonate groups has been furnished by FTIR spectra. which was supplanted by FTNMR results. Estimation of the zinc sulphonate group was done using spectroscopic techniques such as XRFS and ICPAES. The TGA results prove improvement in the therrno-oxidative stability of the modified natural rubber. Both DSC and DMTA studies show that the incorporation of the ionic groups affect the thermal transition of the base polymer. Retention of the improved physical properties of the novel ionomers even after three repeated cycles of mastication and molding at 120 degree C may be considered as the evidence for the reprocessabiJity of the ionomer. Effect of both particulate (carbon black. silica & zinc stearate) and fibrous fillers (nylon & glass) on the properties of the radiation induced styrene grafted natural rubber ionomer has been evaluated. Incorporation of HAF carbon black results in maximum improvement in physical properties. Silica reinforces the backbone chain and weakens the ionic associations. Zinc stearate plays the dual role of reinforcement and ptasticization. The nylon and glass filled lonorner compounds show good improvement in the physical properties in comparison with the neat ionomer. Dispersion and adhesion of the fillers in the ionomer matrix has been amply supported by their SEM micrographs. Microwave probing of the electrical behavior of the 26.5 ZnSRISGNR ionomer reveals that the maximum relative complex conductivity and the complex permittivity appear at the frequency of 2.6 GHz. The complex conductivity of the base polymer increases from 1.8x 10.12 S/cm to 3.3xlO·4 S/cm. Influence of fillers on the dielectric constant and conductivity of the new ionic thermoplastic elastomer has been studied. The ionomer I nylon compound shows the highest microwave conductivity. Use of the 26.5 ZnS-RISGNR ionomer as a compatibilizer for obtaining the technologically compatible blends from the immiscible SBR/NBR system has been verified. The heat fugitive ionic cross-linked natural rubber may be, therefore, useful as an alternative to vulcanized rubber and thermoplastic elastomer

Dielectric properties of ionomers at microwave frequencies

Ionic polymers (ionomers) with interesting characteristics are emerging as important commercial polymers. Ionomers have the unique ability to behave as cross-linked materials at ambient temperatures and to melt and flow at elevated temperatures like thermoplastics. The complex permittivity and conductivity of a class of ionomers at microwave frequencies are determined using the cavity perturbation technique and the results are presented.

Synthesis and Characterization of Novel Ionomers based on Styrene Butadiene Copolymer

Novel thermo-reversible zinc sulphonated ionomers based on styrene butadiene rubber (SBR), and high styrene rubber (HSH) were synthesized by sulphonation followed by neutralization with zinc. The sulphonate content of the ionomer was estimated by using x-ray fluorescence spectroscopy. Presence of sulphonate groups has been confirmed by FTIR and FTNMR spectra. The TGA results show improvement in the thermo~oxidative stability of the modified rubber. Both DSC and DMTA studies show that the incorporation of the ionic groups affect the glass rubber transition of the base polymer. lntroduction ol ionic functionality in to the base material improved the physical properties. Retention of the improved physical properties of the novel ionomers even after three repeated cycles of mixing and molding may be considered as the evidence for the reprocessability of the ionomer. Effect of particulate fillers (HAF black, silica and zinc stearate) on the properties of the zinc sulphonated styrene butadiene rubber ionomer has been evaluated. Incorporation of tillers results in improvement in mechanical properties. Zinc stearate plays the dual role of reinforcement and plasticization. The evaluation of dielectric properties of zinc sulphonated styrene butadiene rubber iorpmers at microwave frequencies reveal that the materials show conductivity at semiconductor level. The real and imaginary parts of the complex permittivity increases with increase in ionic functionality. Use of the 38.5 ZnS-SBR ionomer as a compatibiliser for obtaining the technologically compatible blends from the immiscible SBR/NBR system has been discussed.

High Styrene–Rubber Ionomers, an Alternative to Thermoplastic Elastomers

High styrene rubber ionomers were prepared by sulfonating styrene–butadiene rubber of high styrene content (high styrene rubber) in 1,2-dichloroethane using acetyl sulfate reagent, followed by neutralization of the precursor acids using methanolic zinc acetate. The ionomers were characterized using X-ray fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), dynamic mechanical analysis (DMA), and also by the evaluation of mechanical properties. The FTIR studies of the ionomer reveal that the sulfonate groups are attached to the benzene ring. The NMR spectra give credence to this observation. Results of DMA show an ionic transition (Ti) in addition to glass–rubber transition (Tg). Incorporation of ionic groups results in improved mechanical properties as well as retention of properties after three cycles of processing