[en] We have performed a quantum-chemical investigation on the conformations and electronic properties of a variety of methoxy-substitute poly(p-phenylenevinylenes) (PPVs) to elucidate the effects of alkoxy substitution. Geometrical parameters for the polymers were fully optimized through Austin Model 1 (AM1) semi-empirical Hartree-Fock (HF) band calculations. Electronic properties of the polymers were obtained by applying the AM1 optimized structures to the modified extended Hueckel method. To confirm validity of the AM1 conformational results, we also carried out ab initio HF calculations with the 6-31G (d) basis set for a variety of methoxy-substituted divinylbenzenes. It is found that the potential energy surfaces of alkoxy-substituted PPVs are quite shallow around the planar conformations, suggesting that the prepared films possess a variety of conformations with different torsion angle in the solid state, depending on the synthetic conditions, When two alkoxy groups are con-currently substituted at the adjacent sites in the phenylene ring, these group are subject to rotating around the C(sp²)-O bonds by 70-80.deg. to avoid the strong steric repulsion between them. Consequently, the overlap between the π-type p orbital of oxygen and the π molecular orbitals of the polymer decreases. This leads to a wide gap and a high oxidation potential for tetramethoxy-substituted PPV, compared to those of dialkoxy-substituted PPV

[en] Controlling heat accumulation is one of the major challenges for block materials synthesizing via bulk polymerization. In the paper, cross-linked polystyrene was successfully fabricated by the combination of bulk polymerization and gamma-ray irradiation in the range of 8.5-34.0 kGy. The cross-linking network structures were characterized by Fourier transform infrared spectrometer and dynamic mechanical analysis. The thermal stability and the mechanical properties were analyzed as well. Results showed that the products synthesized at dose of 34.0 kGy with dose rate of 40 Gy/min achieved the best mechanical strengths. The thermal stability could be improved with the increase of dose ranging from 8.5 to 34.0 kGy. (author)

[en] Anion exchange resins based on the copolymer of 4-vinylpyridine-divinylbenzene were synthesized in the presence of solvents. It was observed that the resins obtained with 8% divinylbenzene gave best chloride capacities. These resins were methylated to get strong base anion exchange resins for uranium hydrometallurgy with basic solution. The resin obtained with tertiary amyl alcohol and 8% divinylbenzene gave the best uranium adsorption capacity. This resin was compared with the commercial resin Dowex SBR-P which gave a lower capacity. The strong base and weak base chloride capacities and porosity data of this are reported. (author)

[en] Polystyrene-Divinylbenzene based ion exchange resins are widely used in purification processes in the nuclear industry. Generally, performance of ion exchange resin in purification system depends on the properties of ion exchange resin (viz. salt splitting capacities, cross linking, uniformity coefficient etc.) along with the different process parameters such as purification flow, temperature and differential pressure across the resin bed. However, in a nuclear reactor, presence of ionising radiation plays a very crucial role on the performance of ion exchange resin. Resin in such systems is subjected to an intense radiation exposure which significantly reduces its operational life and leads to generation of excessive radioactive waste. To assess the governing factors, a radiation stability study on ion exchange resin was carried out using a γ radiation source and by analysing a comprehensive set of samples from exhausted ion exchange resins from process systems of reactor. Based on the conclusions drawn from these studies, factors affecting the performance of ion exchange resin in various process systems of nuclear reactors have been discussed and possible remedial measures have been suggested to improve quality and the service life of the ion exchange resins. (author)

[en] Preparation and characterization of nanosized magnetic particles using alkaline oxidation of ferrous ion retained in acrylonitrile-methyl methacrylate-divinylbenzene (AN-MMA-DVB) spherical micron-sized polymer template is described. Atomic absorption, transmission electron microscopy and magnetic resonance were used to investigate chemically cycled nanoparticle-based composites. The resonance field shifts towards higher values as the nanoparticle concentration reduces in the polymeric template, following two very distinct regimes

[en] Complete text of publication follows. A new ionic imprinted polymer for Ni(II) recognition/preconcentration was prepared via precipitation polymerization using 2-(diethylamino) ethyl methacrylate (DEM) and divinylbenzene as a crosslinking agent in the presence of nickel(II) and 5-vynil-8-hydroxyquinoline. It has been demonstrated that Ni(II)-Ionic Imprinted Polymer synthesized by the precipitation polymerization technique from a ternary pre-polymerization complex formed by the template (Ni), the monomer (DEM) and a non-vinylated chelating agent (8-hydroxyquinoline, 8-HQ) offers imprinting properties for the template (Ni(II)) and also for Cu(II), Pb(II) and Zn(II) with analytical recoveries close to 100% for all elements. Since the complexing agent (8-HQ) is trapped into the polymeric matrix, but is not linked to the polymer chains, specific interactions between the functional groups (present in the monomer and the complexing agent) and other trace elements rather than Ni may occur. To overcome this lack of selectivity a new monomer (5-vynil-8-hydroxyquinoline) was synthesised and submitted to the same polymerization process, in order to fix the 8-HQ to the polymeric matrix, avoiding the 'flexibility' of the imprinting cavities, and so, improving selectivity. Results have shown that the new IIP is more selective than the previous polymer. In addition, the polymer does not interact with alkaline or alkaline-earth metals, so Na, K, Mg and Ca from the seawater salt matrix could be effectively removed. Variables affecting the IIP-solid phase extraction (SPE) process (pH, load and elution flow rate and concentration and volume of the eluting solution) were completely studied. ICP-OES has been used as multi-element detector. Acidified seawater samples must only be treated to fix an alkaline pH (9.00.1) and passed through IIP-SPE cartridges. After seawater sample loading (100 mL), analytes were eluted with 2.5mL of 2.0M nitric acid, offering a pre-concentration factor of 40. The limit of detection (LOD) of the method was 0.26 μg l^-1, while the relative standard deviation was 3% (n=11). Accuracy of the method was assessed by analyzing SLEW-3 (estuarine water) and TM-23.3 (lake water) certified reference materials.

[en] To achieve a suitable porous structure and high mechanical strength that is extremely valuable properties in adsorbent polymeric particles, poly(styrene-co-divinylbenzene) with high amounts of cross-linker and diverse proportions of diluent agent (porogen) were synthesized according to the methodology of the suspension polymerization technique. The structural characteristics of the particles and their adsorption properties for adsorption of Nickel ions were studied. Effect of solvent type and monomeric fraction on particles morphology and porosity was discussed. The solvents including n-heptane (HEP) and acetonitrile and monomer fraction was 50% and 30% of divinylbenzene (DVB). From the results obtained, we decided to apply an adsorbent with high mechanical strength and a porous structure appropriate for absorbing the Ni(II). The copolymer was characterized by Fourier transform infrared (FT-IR) analysis. We used scanning electron microscopy (SEM) and transmission electron microscopy (TEM) tests to study the morphology and particle size of the nanoparticles. According to the results, the copolymers synthesized with n-heptane have more porosity. Also an increase in the percentage of DVB caused finer pores. After synthesis of copolymer the applicability of these polymer beads to separation and concentration of Ni(II) is discussed. In separation of Ni(II) from aqueous solution, the effects of pH, temperature and time are discussed and thermodynamic and kinetic calculations are done and its isotherm are fitted with various equations.

[en] Acidic and basic porous polymers were facilely prepared through the radical copolymerization of target monomers and the crosslinker divinylbenzene (DVB), respectively. Combination of these polymers endowed highly efficient, heterogeneous recyclable acid-base binary catalysts for cascade deacetalization-Knoevenagel reaction, offering high yield and stable reusability. Binary polymers with strong acid sites and superior base sites afforded an unprecedented turnover frequency (TOF) in the condensation of benzaldehyde dimethylacetal and nitriles (285 h⁻¹ for malononitrile and 57 h⁻¹ for inert methylene substrate ethyl cyanoacetate). The excellent synergistically catalytic performance was ascribed to the unique self-protection effect of the in-situ formed acid and base sites embedded in the polymeric network. This study provided a facile, versatile and efficient strategy towards acid-base bifunctional heterogeneous catalysts by combining acidic and basic porous polymers.

[en] A number of copolymers were synthesized by the reaction of N-vinyl carbazole (NVC) and divinylbenzene (DVB) by using the technique of suspension polymerization. A mixture of cyclohexanone (CHN) and petroleum ether of various composition was used as a diluent in the polymerization experiments. The copolymers were characterized for the density, pore volume, pore size distribution, surface area and mechanical strength. The copolymers were also converted into cation-exchange resin by sulfonation and the resulting resins were characterized for the ion-exchange capacity. The pore volume of the copolymers decreases from 1.26 to 0.19 ml/g and 1.09 to 0.46 ml/g with the decrease in pet. ether or increase in CHN ratio of organic phase, with the decrease in the amount of diluents as compared to monomers (F/sub s/) and with the decrease in the crossing agent, DVB, respectively, used in the respective polymerization experiments. The apparent density of the copolymers varies from 0.55 to 0.25 g/ml, 0.55 to 0.27 g/ml and 0.45 to 0.28 g/ml with the percentage increase in the ratio of pet. ether from 0 to 100% as compared to CHN, with the increase in solvent fraction from 0.3 to 0.8 and with the increase in DVB from 5 to 40%, respectively. The relatively larger size pores were observed in the beads of copolymers formed with the increase in the pet. ether contents of the diluents, increase in the amount of diluents as compared to monomers and also with the increase in the crossing agent. The capacity of NVC-DVB cation-exchange resins decrease slightly from 4.89 to 4.00 meq/g with the increase in the crosslinking agent from 5 to 40% whereas it does not change significantly with change in the composition and the amount of diluents used polymerization experiments under the given experimental conditions. The mechanical strength (crushing load) of the copolymer beads increased with the increase in CHN ratio from 0 to 100% in diluents mixture, with the decrease in solvent fraction from 0.8 to 0.3 and with the decrease in the crosslinking agent (DVB) from 40 to 5%. The crushing load also increase with the increase in the overall size of the copolymer beads. (author)

[en] Chelating resins have been prepared from acrylonitrile-divinylbenzene copolymer beads produced by suspension polymerization in in presence of an inert diluent. The copolymer beads were reacted with hydroxylamine to produce amidoxime groups in the repeating units derived from cyano groups (acrylonitrile), varied reaction conditions were employed. In this study, a set of experiments have been performed to determine the potential of the amidoxime chelating resin for the adsorption of gallium from Bayer liqueur. (author)