Showing papers in "Reactive & Functional Polymers in 1996"

Photograft-polymer-modified microporous membranes with environment-sensitive permeabilities

Abstract: Intraporous heterogeneous modification of commercial nylon (Ny) and polypropylene (PP) microfiltration membranes, both of 0.2 μm pore size, with grafted poly(acrylic acid) (g-PAA) was accomplished by first coating the membranes with a photoinitiator, benzophenone (BP), and then UV irradiation in acrylic acid (AA) solutions in water. The degree of modification (DG) depended strongly on AA concentration (cAA) and UV time. As estimated from PAA homopolymer GPC analyses, average degrees of graft polymerization between 680 and 2200 were achieved by varying cAA between 10 and 50 g/l. PP-g-PAA and Ny-g-PAA membranes were characterized with scanning electron microscopy, revealing outer and intraporous surface coverage with g-PAA. FTIR-ATR and energy-dispersive X-ray spectroscopy data verified the chemical composition and a gradient of DG over membrane thickness, but modification also of the bottom layer. Membrane swelling and permeabilities depending on DG and pH — above and below pKgPAA — were studied. PP-g-PAA membranes were almost dimensionally stable, and with intermediate DG (around 1 mg/cm2) the ‘switch height’ of transmembrane permeability as function of pH was very high (by a factor of 100, even in 100 mM buffer). Ny-g-PAA membranes markedly changed the shape due to modification, swelling and additional pH changes; the mechanical stability — especially at DG > 1 mg/cm2 — was poor, and the permeability response to pH was less pronounced. Thus, the differences in membrane material hydrophilicity caused different modification surface selectivity, which for Ny was reduced due to sorption of BP and AA during coating and polymerization, respectively. Two different types of graftpolymer-modified microporous membranes resulted: almost ‘perfect’ pore filling for PP-g-PAA, but simultaneous matrix and pore modification for Ny-g-PAA.

Adsorption characteristics of arsenic(III) and arsenic(V) on iron(III)-loaded chelating resin having lysine-Nα,Nα-diacetic acid moiety

Abstract: An iron(III)-loaded chelating resin (Fe-LDA) with lysine-N α ,N α -diacetic acid functional groups has been prepared and its adsorption characteristics for arsenic(III) and arsenic(V) have been examined. Arsenic(V) was strongly adsorbed to the resin in the pH range from 2 to 4, while arsenic(III) was moderately adsorbed between pH 8 and 10. The isotherm data for arsenic(V) at pH 3.5 fitted well to a Langmuir equation with a very large binding constant of 7.2 × 10 4 dm 3 mol −1 and a capacity constant of 0.74 mmol g −1 The data for arsenic(III) at pH 9 also fitted to a Langmuir equation, with a binding constant of 190 dm 3 mol −1 and a capacity constant of 0.84 mmol g −1 . Regeneration of the resin was successfully carried out with 0.1 mol dm −3 sodium hydroxide solution. Both arsenic compounds can be almost quantitatively recovered from the resin under these conditions. Only a small amount of ferric ions (less than 0.1 %) was observed to come off the resin during the regeneration with alkaline solutions. Since the Fe-LDA resin showed little affinity for arsenic(III) in acidic media, the present adsorption system can provide satisfactory separation of arsenic(V) from arsenic(III). Arsenic(V) was successfully concentrated in the column packed with Fe-LDA resin from its dilute solution.

Recent advances in synthesis of high-temperature aromatic polymers

Abstract: This paper reviews our current studies on the synthesis of high-temperature aromatic polymers with emphasis on the synthesis of new classes of aromatic polymers and also on the exploration of new synthetic methods for aromatic polymers as well. The first topic is the synthesis of new soluble aromatic polymers having high glass-transition temperatures above 300°C, such as aramids and polyimides, starting from a variety of aromatic diamines that have bulky pendant phenyl groups or crank and twisted non-coplanar structures. The second is the preparation of novel polyimide-silica hybrid materials via a sol-gel process. The third is the rapid microwave induced synthesis of polyamides and polyimides. The fourth is the high pressure synthesis of polyimides and polybenzoxazoles.

Polyimides derived from nonaromatic monomers: synthesis, characterization and potential applications

Abstract: A number of mixed aromatic/cycloaliphatic as well as fully nonaromatic polyimides have been prepared. Whereas all the poly(amic acids) derived from nonaromatic diamines involved salt-formation during the initial stages of the polymerization, the majority of these eventually formed homogeneous, highly viscous polymer solutions. Only in a few select cases involving all nonaromatic monomers traditional solution polymerization was unsuccessful. The polyimide derived from hexafluoroisopropylidene diphthalic anhydride (6FDA) and trans- 1,4-diaminocyclohexane (DACH) yielded films with tough mechanical properties, a glass transition temperature of ∼360°C, good solvent resistance, and a low dielectric constant of 2.6. Thermal stability of this polyimide as determined by thermal gravimetric analysis in both air and nitrogen was quite good, exhibiting a weight loss of only 0.07 wt%/h at 350°C under isothermal conditions in nitrogen. However, mechanical properties as a function of thermal aging in both air and nitrogen indicated a maximum use temperature of only 350°C under inert conditions and less than 300°C in the presence of oxygen.

Adsorptive recovery of naphthenic acids using ion-exchange resins

Abstract: Adsorption of naphthenic acids has been studied on commercial weak and strong anion-exchange resins. The capacity and equilibrium constant of adsorption on these resins are compared with those obtained with zeolites, bentonite and polyvinyl pyridine. Macroporous weakly anionic ion-exchange resins with weak tertiary amine group have good adsorption capacity for the removal of naphthenic acids from petroleum oil as compared to strong anion-exchange resins with isoporous structure although the strong anion-exchange resin shows greater interaction with naphthenic acids. The rate of uptake of naphthenic acid is governed by the internal diffusional resistance which is also dependent on adsorbed phase concentration.

Synthesis and enzymatic degradation of regular network aliphatic polyesters

Abstract: Regular network aliphatic polyesters were prepared from glycerol (Yg) and a series of various length aliphatic dicarboxylic acids (HOOC-(CH2)n−2-COOOH, n = 4–10, 12 and 14). Prepolymers prepared by melt polycondensation were cast from dimethylformamide solution and post-polymerized at 230°C for various times to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. The degree of reaction (DR) estimated from the infrared absorbance of -OH and >CH2 or >CH groups increased with increasing post-polymerization time and length of methylene chain. The heat distortion temperature also increased with increasing post-polymerization time and was 55, 28, 15, 6, 0, −1, −5, 4 and 32°C for Yg4, Yg5, Yg6, Yg7, Yg8, Yg9, Yg10, Yg12 and Yg14 post-polymerized for 4 h, respectively. Wide angle X-ray scattering patterns showed a distinct single diffraction peak, suggesting some ordered structure due to the establishment of a regular network. Density, water absorption and weight loss by alkali hydrolysis decreased with increasing methylene chain length. The enzymatic degradation was estimated by weight loss of the network films in a buffer solution of lipase at 37°C. The films of Yg4, Yg5, Yg6 and Yg7 showed no weight loss, but the weight loss increased greatly for Yg8, Yg9 and Yg10, and then decreased abruptly for Yg12 and Yg14. This suggests that the enzymatic degradation is affected by network structure, which allows the lipase to penetrate, and by the concentration of the enzymatically degradable ester linkage.

Swellable ethylene glycol dimethacrylate-hydroxyethylmethacrylate copolymer beads

Abstract: In this study, Swellable poly(EGDMA/HEMA) beads in the size range of 30–170 μm with different size distributions were produced by suspension copolymerization of ethylene glycol dimethacrylate (EGDMA) and hydroxyethylmethacrylate (HEMA) in aqueous media. Poly(vinyl alcohol) and benzoyl peroxide were used as the stabilizer and the initiator. The diluent, i.e. toluene was included in the recipe of the second group of copolymerizations. The beads were characterized by optical microscopy, FTIR and FTIR-DRS. Crosslinked, transparent, nonporous and Swellable (up to a swelling ratio of 31.2%) poly(EGDMA/HEMA) beads were obtained in which there was no toluene in the recipe. While copolymerizations with toluene provided Swellable (up to a swelling ratio of 57.1%), opaque, porous and crosslinked copolymer beads. In the polymerization (without toluene) HEMA is mainly incorporated on the outer layers (near surface) of the beads. In this case, increase in the EGDMA/HEMA ratio resulted larger beads with wider size distributions, and with lower swellabilities. The porosity of the dry copolymer beads were studied with mercury pycnometric method. Incorporation of toluene within the recipe (in the modified polymerization) caused pronounced effects both on bead size and swellability. Larger beads with broader size distributions, with higher swellabilities were obtained when the relative amount of toluene increased.

High-temperature polyimide nanofoams for microelectronic applications

Abstract: Foamed polyimides have been developed in order to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the nanometer range, thus, the term ‘nanofoam’. The polyimide foams are prepared from block copolymers consisting of thermally stable and thermally labile blocks, the latter being the dispersed phase. Foam formation is effected by thermolysis of the thermally labile block, leaving pores of the size and shape corresponding to the initial copolymer morphology. Nanofoams prepared from a number of polyimides as matrix materials were investigated as well as from a number of thermally labile polymers. The foams were characterized by a variety of experiments including TEM, SAXS, WAXD, DMTA, density measurements, refractive index measurements and dielectric constant measurements. Thin film foams, with high thermal stability and low dielectric constants approaching 2.0, can be prepared using the copolymer/nanofoam approach.

Esterification of formic acid, acrylic acid and methacrylic acid with cyclohexene in batch and distillation column reactors: ion-exchange resins as catalysts

Abstract: Esterification of formic acid, acrylic acid and methacrylic acid with cyclohexene was carried out in the presence of cation-exchange resins as catalysts. Effect of various parameters, e.g. speed of agitation, catalyst particle size, catalyst loading, types of catalyst, temperature, mole ratio of the reactants, was studied to optimise the reaction conditions. The reaction of formic acid, with different concentrations in aqueous solutions, with cyclohexene was studied. Experiments were carried out in the presence of homogeneous catalyst, p-toluene sulphonic acid (p-TSA), to compare results with the heterogeneous catalyst. A comparison of anhydrous esterification between acrylic acid and that of methacrylic acid with cyclohexene has been reported. The conversion of formic acid in aqueous solutions to cyclohexyl formate, by reaction with cyclohexene, in a distillation column reactor (DCR), packed with an acidic ion-exchange resin catalyst was studied; the effect of variables such as feed flow rate, molar ratio of reactants, amount of catalyst in the reboiler, concentration of formic acid, location of the feed point, etc., was studied. A comparison between the rate of esterification of formic acid with cyclohexene in batch mode and in distillation column reactor has been made. An attempt was also made for the selective esterification of formic acid with cyclohexene from a mixture of formic acid and acetic acid in a DCR.

Synthesis of polymer-supported calix[4]arenes and selective extraction of Fe3+

Abstract: Three polymeric calix[4]arenes were synthesized by reacting chloromethylated polystyrene with 25,26,27-tribenzoyloxy-28-hydroxy calix[4]arene (2a, 3a) and polyacryloyl chloride with 25,26,27,28-tetraacetoxy calix[4]arene (4a). After alkaline hydrolysis of the polymers, they were utilised for selective extraction of some transition metal cations from aqueous phase to organic phase. It was found that the polymeric calix[4]arenes were selective to extract Fe3+ from an aqueous solution which contained Cu2+, Ni2+, Co2+, and Fe3+ cations and it was observed that the polymer supported onto the lower rim calix[4]arene is a more efficient carrier of Fe3+ in the extraction process.

Alkali Blue 6B-attached poly(EGDMA-HEMA) microbeads for removal of heavy-metal ions

Abstract: In this study, we investigated a new sorbent system, i.e., Alkali Blue 6B-attached poly(EGDMA-HEMA) microbeads, for removal of heavy-metal ions from aqueous solutions. Poly(EGDMA-HEMA) microbeads were prepared by suspension copolymerization of ethyleneglycoldimethacrylate (EGDMA) and hydroxyethylmethacrylate (HEMA) by using poly-(vinylalcohol), benzoyl peroxide and toluene as the stabilizer, the initiator, and the diluent, respectively. Alkali Blue 6B molecules were then covalently attached to these microbeads. Microbeads (150–200 μm in diameter) with a swelling ratio of 55%, and carrying 23.6 μmol Alkali Blue 6B/g polymer were used in the adsorption/desorption studies. Adsorption rate and capacity of the microbeads for the selected metal ions, i.e., Cd(II), Cu(II), Zn(II) and Pb(II) were investigated in aqueous media containing different amounts of these ions (1–500 ppm) and at different pH values (1.5–7.5). Very high adsorption rates were observed at the beginning, and adsorption equilibria were then gradually achieved in about 5–90 min. The maximum adsorptions of metal ions onto the Alkali Blue 6B-attached microbeads were 5.5 mg/g for Cd(II), 2.3 mg/g for Cu(II), 41.4 mg/g for Zn(II), and 125 mg/g for Pb(II). However, when the metal ions competed (in the case of the adsorption from their mixture) the amounts of adsorption for Cd(II), Zn(II) and Pb(II) were quite close. Desorption of metal ions were studied by using 0.1 M HN03 (pH 1.0) for Cd(II), Cu(II), Zn(II) and Pb(II) ions. High desorption ratios (more than 90%) were achieved in all cases. Adsorption/desorption cycles showed the feasibility of repeated use of this novel sorbent system.

Solvent impregnated resin (SIR) containing dialkyl dithiophosphoric acid on Amberlite XAD-2: extraction of copper and comparison to the liquid-liquid extraction

Abstract: The extraction of Cu(II) from chloride solutions at 0.19 M Cl − ionic strength by solvent impregnated resins (SIR) containing di-(2-ethylhexyl) dithiophosphoric acid (DEHTPA) on the Amberlite XAD-2 polymeric support has been studied. The distribution of DEHTPA between the aqueous phase and the resin phase was determined as a function of both pH and loading of DEHTPA ligand (HL) on the resin. The Cu(II) extraction are presented as plots of log distribution coefficient versus pH and DEHTPA concentration in the resin phase. Graphical and computer, analysis showed that the extraction of Cu(II) can be explained by the formation of metal complexes in the resin phase of CuCl 2 (HL) 8 and CuCIL(HL) 8 composition with values of equilibrium extraction constants K ′ = 9.19 max 9.41 and K ″ = 7.69 max 7.99, respectively.

Separation and concentration of calcium and magnesium from sea water by carboxylic resins with temperature-induced selectivity

Abstract: Processes of concentration and separation of calcium and magnesium from artificial and natural sea water by carboxylic ion-exchange resins of acrylic and methacrylic types at different temperatures have been investigated. The values of equilibrium separation factor α for Ca2+Na+, Mg2+Na+ and Ca2+Mg2+ exchanges in ternary systems have been determined in the temperature range of 10°C to 80°C. A significant increase of a values at elevated temperatures has been observed in the first two cases while for Ca2+Mg2+ exchange less remarkable temperature dependence of α can be distinguished. This effect has been shown to allow a selective thermostripping of Ca2+ and Mg2+ from the resins equilibrated at 80°C with sea water in applying cool sea water at 10°C. The thermostripping leads to a selective desorption of both Ca2+ and Mg2+ while Na+ ions remain sorbed, resulting in the increase of Ca2+ and Mg2+ concentration in the eluate up to 50% (in comparison with the initial sea water) and a decrease of 10% for Na+ concentration. These results may be considered as unique in polythermal concentration in comparison with, e.g. conventional evaporation technique. The results of consecutive sorption-thermostripping cycles have shown the possibility to concentrate calcium and magnesium from natural sea water more than three times by applying reagentless (and wasteless as a result) ion-exchange technique. The results of frontal separation of Ca2+ and Mg2+ on acrylic resin in Na+-form from natural sea water and thermostripping solutions obtained are also presented. The novel approach for forecasting temperature dependences of the resin selectivity has been proposed. The approach is based on a thermodynamic interpretation of the results obtained that allows to predict the temperature dependences of both αa (for binary Mg2+Na+ exchange) and the apparent equilibrium constant of ternary Na+Ca2+Mg2+ exchange.

Syntheses of thiacrown ethers polymers and their application for heavy metal ion adsorbents

Abstract: 6-(4′-Vinylbenzyloxy)-1,4,8,11-tetrathiacyclotetradecane (S14S4) and 9-(4′-vinylbenzyloxy)-1,4,7,14,17-hexathiacycloeicosane (S20S6) were synthesized as thiacrown ether monomers by using a high dilution cyclization method. The thiacrown ether monomers were polymerized and copolymerized with styrene (St) and N -vinylpyrrolidone (NVP) by radical polymerization. Their affinity for the solvent was easily controlled by choosing the comonomer used. The thiacrown ether polymer ligands had binding selectivity for Ag(I) and Hg(II) ions like as a polymer ligand having acyclic polythioether units. The binding ability, however, was not affected by the shape of the thioether (either a cyclic ether or an acyclic ether) and by the copolymer composition. They can be used as an adsorbent under acidic condition and can reused repeatedly.

Preconcentration of mercury(II) on dithizone anchored poly(vinyl pyridine) support

Abstract: Dithizone, a selective and sensitive reagent for mercury, was anchored on cross-linked poly(vinyl pyridine) and was used for the preconcentration of nanogram levels of mercury. The polymeric support was characterised for the extent of coupled dithizone and thermal properties. The support was used in batch and column experiments for the preconcentration of mercury. Various conditions such as pH, temperature, flow rate and column parameters were optimised for the maximum extent of mercury loading. Figures exceeding 140 mg/g support were achieved at optimised conditions. Mixture of 0.2 M nitric acid and 2.0% ammonium nitrate in 1 : 1 proportion elutes mercury quantitatively. Separation of mercury from binary and ternary mixtures of mercury, palladium, zinc and cadmium was achieved without any cross-contamination.

A study on the exchange kinetics of ion-exchange fiber

Abstract: In this paper, the ion-exchange kinetics of ion-exchange fiber has been studied. Under Finite Solution Volume (FSV), not only the effect of temperature, speed of stir, concentration and Ph value of the solution on the heterophase isotope exchange has been investigated, but the analytical solution of the exchange equation have also been obtained. By use of these solutions, the intraparticle diffusion coefficients D and the film transmitting coefficients D/δ under different conditions were calculated. Meanwhile, the reason why the ion-exchange rate of fiber is much faster than that of conventional spherical resins was also given with a proposed mechanism.

Solvent impregnated resins: relation between impregnation process and polymer support morphology I. Di-(2-ethylhexyl)dithiophosphoric acid

Abstract: The relationship between polymer support morphology and adsorption of di-(2-ethylhexyl)dithiophosphoric acid (DEHTPA) from alcoholic solution has been studied. As polymer supports investigated are the conventional commercial polymer adsorbents Amberlite XAD-2 and XAD-4 and two microporous polymer adsorbents prepared by post-polymerization crosslinking of swollen chloromethylated gel-type and macroreticular copolymers of styrene and divinylbenzene. Their morphology has been studied by nitrogen adsorption/desorption method. It was found that in the adsorption process DEHTPA fills the pore space gradually from the smallest pores up to pores with a diameter of approximately 10 nm.

Soluble and colorless polyimides with polyalicyclic structures [1]

Abstract: Two tetracarboxylic dianhydrides with polyalicyclic structure, bicyclo[2.2.2]octane-2- endo , 3- endo , 5- exo , 6- exo -2,3:5,6-dianhydride ( 5a ) and the all- exo isomer ( 5b ), were synthesized in six steps using phthalic acid as a starting material. The dianhydrides were polymerized at 85–105°C in well-purified DMAc with aromatic diamines which were purified by two recrystallizations and then sublimation. The polyimides formed flexible and tough films, and were soluble in aprotic polar solvents such as DMAc. The 5%-weight loss temperatures were over 450°C. The polyimides possessed glass-transition temperatures in the range from 211 to 385°C. The polyimides films had a tensile modulus range of 1.5–2.6 GPa, a tensile strength range of 52–96 MPa, and an elongation range at break of 3–11%. The polyimide films showed cutoffs at wavelengths shorter than 320 nm and were entirely colorless. The colorlessness of the polyimide films was maintained up to 200°C when heated in air and to 400°C in a N 2 atmosphere.

New positive-type photosensitive polyimide: poly(hydroxyimide) with diazonaphthoquinone

Abstract: A positive working photosensitive polyimide based on polyhydroxyimide (PHI) and 2,3,4-tris[1-oxo-2-diazonaphthoquinone-4-sulfonyloxy] benzophenone (D4SB) as a photoreactive compound has been developed. The PHI was prepared by the ring-opening polyaddition of 4,4′-hexafluoroisopropylidenebis(phthalic anhydride) (6FDA), 4,4′-diamino-4″-hydroxytriphenylmethane (DHTM), and 4,4′-oxydianiline (ODA), followed by thermal cyclization in refluxing xylene. The PHI film showed excellent transparency to UV light. The photosensitive polyimide containing 30 wt% of D4SB showed a sensitivity of 250 mJ/cm 2 and a contrast of 5.2 when it was exposed to 436 nm light followed by developing with a 1% aqueous tetramethylammonium hydroxide (TMAH) solution at 35°C.

Deactivation of ion-exchange resin catalysts. Part I: Alkylation of o-xylene with styrene

Abstract: The alkylation reaction of o-xylene with styrene was studied by using various cation-exchange resin catalysts. Amberlyst-15 catalyst was found to deactivate on repeated use. This deactivation was studied from the viewpoint of pore structural alterations. The pore structure data of the virgin and deactivated catalyst were analysed by using various techniques such as mercury porosimetry, BET surface area and SEM. The cause and mode of deactivation were investigated by carrying out series of experiments by altering different reaction parameters such as temperature, mole ratio, mode of addition of styrene, divinylbenzene content of the resin, etc. The results focus on the limitations of the ion-exchange resin catalysts, especially with reactants that can form polymeric chains with the matrix.

Preparation of polyimide-epoxy composites

Abstract: The formation of a three dimensional network of crosslinked epoxy leads all unmodified epoxies to have inherent brittleness and relatively low degradation temperatures. Polyimides, on the other hand, are widely used for applications that require high degrees of flexibility and thermal resistance. Here, we have focused on the preparation of epoxy systems cured with polyamic acids instead of traditional amino-group-containing hardening agents. The cure behavior and potential reaction mechanisms of EPON 828 resin and polyamic acid mixtures were evaluated by DSC and TGA. Thermal analysis showed a complex reaction sequence taking place in the mixture and also determined the extent of reaction of the polyamic acid with itself and the competitive reaction of the polyamic acid with the epoxy. The compositions of the mixtures were varied to see the dependence of the cure behavior on component concentrations. Solutions of the two components did not phase separate and also phase separation was not apparent either optically or microscopically in the cured samples. This phase behavior was attributed to a unique in situ reaction. A novel solvent system for the polyamic acid precursor was also used.

A novel phosphine sulphide functionalized polymer for the selective separation of Pd(II) and Au(III) from base metals

Abstract: Two new insoluble extractant systems based on a derivated polystyrene have been prepared for the separation and recovery of precious metals. This functional polymer has been obtained by the incorporation of a phosphine sulphide on the Merrifield polymer. This incorporation has been made by either direct attachment to the polymer or through on alkyl chain as spacer between the polymeric backbone and the phosphine sulphide unit. The spacer consists of a tris-ethoxylated chain to provide hydrophilic properties. Adsorption of metals Au(III) or Pd(l1) from chloride solutions have been studied for the different polymers prepared and by varying the composition of the metal solution with mixed aqueous-dioxane media. The results obtained include the polymer capacity and the rate of metal adsorption. Capacity for Pd(II) has been observed much higher than for Au(III) in all cases. The capacity as well as the adsorption rate are enhanced by the incorporation of the spacer in the polymer and also by the presence of dioxane in the metal solution. On the other hand, the adsorption process has shown to be selective for AU(111) or Pd(II) in presence of the base metals Pb(II), Ni(II) and Cu(II).

Scope in the synthesis and properties of poly(ether imide)s

Abstract: This paper reviews methods of synthesis of dianhydrides for use in poly(ether imide) syntheses. It discusses the synthesis of new dianhydrides from alkyl-substituted diols, catechol and its derivatives and dihydroxynaphthalenes and the synthesis of new poly(ether imide)s from them. The major features of the properties of these groups of polymers, especially those of highly processable poly(ether imide)s, are discussed and potential applications are considered.

Novel aromatic macrocyclic oligomers: intermediates for the preparation of high-performance polymers

Abstract: Recent studies aimed at the development of macrocyclic oligomers as the intermediates for the preparation of high-performance polymers are reviewed. Efficient methods for the preparation of a range of cyclic oligomers, such as aryl ether ketones, aryl ether phthalazines, aryl ether isoquinolines, aryl ether phthalazinones, and arylene sulfides, have been developed. Cyclization was achieved via a nucleophilic aromatic substitution reaction under high-dilution conditions. The cyclic aryl ether oligomers undergo a facile ring-opening polymerization to form high molecular weight polymer. Cyclic oligomers containing an aromatic sulfide linkage also undergo a facile free-radical ring-opening polymerization to form high molecular weight polymers which can be amorphous or crystalline. Due to their low molecular weights, these cyclic oligomers have very low melt viscosities which makes them attractive intermediates for a variety of applications for which the conventionally prepared high molecular weight polymers would not be suitable.

Poly(β -malic acid) derivatives with unsaturated lateral groups: epoxidation as model reaction of the double bonds reactivity

Abstract: Poly(β-malic acid) derivatives bearing a lateral allyl or 3-methyl-3-butenyl ester group have been prepared by anionic ring opening polymerization or copolymerization of 4-allyloxycarbonyl-2-oxetanone or 4-[3-methyl-3-butenyloxycarbonyl]-2-oxetanone and 4-benzyloxycarbonyl-2-oxetanone as comonomer. These new chiral β-substituted-β-lactones with unsaturated lateral groups have been synthesized from aspartic acid as precursor and by using allylic alcohol or 3-methyl-3-buten-1-ol for opening bromosuccinic acid anhydride, an intermediate compound in the monomer synthesis route. The proportion of unsaturated lateral groups in the polymer was strictly controlled by the proportion of the corresponding lactone in the initial monomers mixture and can vary up to 100%. Functionalized polyesters have been prepared and characterized, and to test the reactivity of the present double bonds, epoxidation has been carried out by using m-chloroperbenzoic acid and dimethyldioxirane as chemical reagents. The activation of the double bond was depending on its chemical environment and on the polymer composition, but quantitative epoxidation has been achieved.

Polystyrene sulfonic acid esters as alkylating agents: preparation of unsymmetrical secondary amines

Abstract: Spherical beads (210–290 μ) of styrene-divinyl benzene (10%) copolymer have been chlorosulfonated and reacted with alcohols to give corresponding sulfonate esters. Their reactions with primary amines, i.e. propyl amine and aniline, give the corresponding secondary amines in reasonable yields (67–76%). The resulting secondary amines are obtained by a simple filtration and distillation. Regeneration of the polymeric support can readily be achieved by acidification and subsequent reaction with thionyl chloride. The present method offers an alternative procedure for the preparation of unsymmetrical secondary amines.

Synthesis and characterization of a 1,2,4,5-tetrazine-modified ion-exchange resin

Abstract: A novel 1,2,4,5-tetrazine functionalized polymer P-Tz was successfully synthesized by the reaction of an aminomethylated macroporous polystyrene-DVB-copolymer (P-Am) with 3-bromo-6-phenyl-1,2,4,5-tetrazine. The proposed structure of the functional groups of P-Tz was confirmed by synthesis of the model compound benzyl-(6-phenyl-1,2,4,5-tetrazine-3-yl)-amine and comparative FTIR-spectroscopic investigations. An application of P-Tz as a redox polymer is not possible due to the cleavage of the tetrazine groups under reducing conditions. Metal sorption and desorption studies of the resin P-Tz were carried out and the results compared with the properties of the weak base anion exchanger P-Am. Evidence is given that the secondary amine spacer of P-Tz influences markedly its over all sorption properties, i.e., the tetrazine-modified resin shows in dilute hydrochloric acid typical anion-exchange properties towards precious metal ions. Compared with the starting polymer P-Am the selectivity sequence found for P-Tz, Pd(II) > Au(III) ⪢ Ir(IV) > Os(IV) > Pt(IV) > Ru(III) > Rh(III), revealed a significantly higher selectivity for Pd(II) which is established even in the presence of an excess of base metals. The results of desorption studies obtained by applying perchloric acid and thiourea as eluting agents led to the assumption that palladium is strongly N-coordinated by the functional tetrazine groups and the secondary amine spacer as well. This hypothesis is confirmed by the structural characterization of a Pd(II)-chelate which is formed during solvent extraction using a monomolecular tetrazine analogue.

Sorption of arsenic anions onto poly(ethylene mercaptoacetimide)

Abstract: A hydrophilic thiol resin, poly(ethylene mercaptoacetimide) (PEM), has been prepared from branched polyethyleneimine of molecular weight 40,000–60,000 by Schotten-Baumann reaction using mercaptoacetyl chloride. The resin with a free mercaptan content of 8.26 meq/g and a standard potential of 0.217 V, as determined by electrochemical measurements, exhibits spontaneous redox sorption of arsenate anions in acidic medium. The saturation capacity for arsenate is 106 mg As/g dry resin at pH 2. The resin, however, sorbs arsenite anions only in alkaline medium and shows a saturation capacity of 30 mg As/g dry resin at pH 8. In addition to redox sorptions, a significant amount of arsenic sorption appears to take place via alternative mechanisms such as complexation by thiol and anion exchange on protonated amine sites of the branched PEM. The sorption of both arsenate and arsenite is significantly reduced by the presence of salts, NaCl and Na2SO4, in solution. The sorption kinetics is controlled by the diffusion of arsenical anions in the resin particle. The sorbed arsenic species are readily stripped by 0.2 N NH4OH and the stripped resin in the oxidized (disulfide) form is reconverted to the active thiol form by treatment with an excess of 10% sodium bisulfite solution

Synthesis of aromatic polyketones by using biphenylene monomers

Abstract: Bisfunctional biphenylene monomers were designed, synthesized, and inspected as building blocks for aromatic polyketone synthesis. Starting from 2,2′-dimethoxybiphenylene (1), a highly activated acyl-acceptant biphenylene monomer affording high molecular weight polyketones, two types of biphenylene monomers were developed: 5,5′-bis(3[4]-chlorobenzoyl)-2,2′-dimethoxybiphenylenes (6) which readily gave the corresponding polyketones by nickel-catalyzed aromatic coupling polymerization and 2,2′-bis(trifluoromethyl)-4,4′-biphenylenedicarboxylic acid (27) which reacted with biphenylene 1 in P2O5CH3SO3H to give the corresponding fluorinated aromatic polyketone, selectively. The related model reactions for both monomer synthesis and polymerization were also investigated.

Synthesis of chelating molecules as agents for magnetic resonance imaging, 31. Polycondensation of diethylenetriaminepentaacetic acid bisanhydride with diols and diamines

Abstract: The polycondensation of diethylenetriaminepentaacetic acid (DTPA) bisanhydride with diols and diamines was investigated in order to obtain new complexing agents bearing aminoacetic groups along the polymer chain whose complexing properties should be better than their monomolecular homologues: EDTA (ethylenediaminetetraacetic acid), DTPA … Synthesis conditions have been studied to get linear water-soluble polymers destined to gadolinium complexation. Use of several types of comonomers has allowed us to obtain polycondensates having a varied density of COOH functions which will permit us to study its influence on their complexing properties towards different metallic cations.