Reactive Polymers最新文献

The structure and properties of macroporous methacrylonitrile (MAN) copolymers are compared with those of acrylonitrile (AN) copolymers. These copolymers are crosslinked with divinylbenzene (DVB) or trimethylolpropane triacrylate (TMPA). All these copolymers were obtained by suspension polymerization from the monomer mixtures containing a good solvent — cyclohexanol and hexadecane. The copolymers are porous and their porosity in the dry state is much higher than in the swollen one. The swelling of these copolymers causes the average pore size to decrease. The kind of crosslinking agent is the most significant factor influencing the porous structure of the copolymers. MAN and TMPA copolymers (MAN-T) have the smallest average pore size and the narrowest pore distribution. Methacrylonitrile copolymers are better sorbents than acrylonitrile copolymers. Their aminolysis by ethylenediamine is much more difficult than that of the latter, but they are both suitable for lipase immobilization.

The thermodynamics of protonation of carboxylate groups in polymers containing amido and isopropyl moieties was studied in 0.1 M NaCl at different temperatures. Compared with polymers with the l-leucine moiety, poly(N-acryloyl-l-valine) showed a wider decreasing linearity of the basicity constant (log K) in relation to the degree of protonation (α), with a minimum at α = 0.65. Under these conditions, a sharp endothermic peak revealed the presence of hydrophobic interactions as the macromolecule assumed a compact coil conformation and water molecules were released with an increase in entropy. The graft polymers on the surface of a polyurethane film displayed larger potentiometric hysteresis loops with respect to the cellulose support, as the nature of the polymer was similar to that of the hydrophobic substrate. The reversible configuration of the graft polymer chains instantly responded to changes in pH and temperature, modifying the rate of water filtration through the membrane pores. As the temperature approached 31°C an abrupt increase in water permeation was observed even though the graft polymer was in the uncharged and coiled state. The polyelectrolyte formed a hydroxo-complex species, involving two monomer units (L⁻) of the polymer, with the Cu(II) ion. Electron paramagnetic resonance (EPR) spectra, supported by conductometric data, revealed Cu(OH)₂L₂²⁻ stoichiometry in solution. The potentiometric data showed a good fit when processed by the Superfit program and a decreasing pattern of log β in relation to pH.

Chitosan is a natural polymer well known for its efficient uptake of heavy metals. The modification of this polymer by the substitution of functional groups from organic acids allows new sorbents with high sorption capacities to be obtained: NDTC with ascorbic acid and glutamate glucan with oxo-2-glutaric acid. The mechanism of sorption is investigated and several sorption models are applied such as the Freundlich, Langmuir and Temkin models which fit experimental results well. These results are explained by the heterogeneity of the polymer surface, the variability of metal species in solution and possible interactions between the molecules sorbed. The effects of several parameters such as pH and metal ion concentration are examined and demonstrate the relative importance of metal speciation on sorption performances and mechanisms. The grafting of functional groups creates some heterogeneity of sorption energy, which explains the selectivity seen in the best models. Metal ions are firstly bound onto more energetic sites (nitrogen groups) and later onto other substituting functions.

The optimum condition for synthesis of 1-(2-aminoethyl)piperazine resin (AEPZR) is molar ratio of reagents, piperazine/Cl = 3.0, reaction temperature 100°C, reaction time 10 h and 1,4-dioxane used as a solvent. The functional group capacity of AEPZR is 2.78 mmol FG/g resin. The structure of the resin was confirmed by FT-IR and elementary analysis. The sorption capacities of AEPZR for Au(III), Pd(II), Ru(III), Os(VI), Pt(IV), Ir(IV) are as high as 5.38, 3.67, 3.46, 3.10, 2.46, 2.24 mmol ion/g resin, respectively. The apparent activation energies of sorption of AEPZR for Au(III) and Pt(IV) are 24 ± 7, 28 ± 4 kJ/mol, individually. The sorption molar ratios (metal ion/FG molar ratio) were determined. The dynamic properties of sorption and elution were studied. Noble metal ions adsorbed on AEPZR can be eluted quantitatively by 2% thiourea in 0.1 mol HCl/l. The sorption mechanism was examined by X-ray photoelectron spectra.