Formation, characterization, and catalytic activities of polymer–metal complexes

Liquid-Crystalline Dispersions of Double-Stranded DNA

In this review, we compare the circular dichroism (CD) spectra of liquid-crystalline dispersion (LCD) particles formed in PEG-containing aqueous-salt solutions with the purpose of determining the packing of ds DNA molecules in these particles. Depending on the osmotic pressure of the solution, the phase exclusion of ds DNA molecules at room temperature results in the formation of LCD particles with the cholesteric or the hexagonal packing of molecules. The heating of dispersion particles with the hexagonal packing of the ds DNA molecules results in a new phase transition, accompanied by an appearance of a new optically active phase of ds DNA molecules. Our results are rationalized by way of a concept of orientationally ordered “quasinematic” layers formed by ds DNA molecules, with a parallel alignment in the hexagonal structure. These layers can adopt a twisted configuration with a temperature increase; and as a result of this process, a new, helicoidal structure of dispersion particle is formed (termed as the “re-entrant” cholesteric phase). To prove the cholesteric pattern of ds DNA molecules in this phase, the “liquid-like” state of the dispersion particles was transformed into its “rigid” counterpart.

Preparation and Characterization of Styrene Bearing Diethanolamine Side Group, Styrene Copolymer Systems, and Their Metal Complexes

The two copolymer systems of styrene bearing diethanol amine side group and styrene were prepared by free radical polymerization method at 60°C in presence of 1,4-dioxane as solvent and AIBN as initiator. Their metal complexes were prepared by reaction of the copolymer used as ligand P(DEAMSt-co-St)L′′ and Ni(II) and Co(II) metal ions, which was carried out in presence of ethanol and NaOH at 65°C for 48 h in pH = 7.5. The structures of the copolymers used as ligand and metal complexes were identified by FT-IR, 1H-NMR spectra, and elemental analysis. The properties of the copolymers used as ligand and metal complexes were characterized by SEM-EDX, AAS, DSC, TGA, and DTA techniques. Then, the electrical properties of the copolymers and metal complexes were examined as a function of the temperature and frequency, and the activation energies (Ea) were estimated with conductivity measurements.

Metal Complexes of Maleimide Compounds

The metal complexation ability of some N-substituted maleimides containing a carboxyl group was investigated. Thus, N-(4-carboxy-phenyl)-maleimide, N-(3-acetoxy-4-carboxy-phenyl)-maleimide and poly[ N-(3-acetoxy-4-carboxy-phenyl)-maleimide] were prepared and complexed with several transition metals, such as Co2+, Ni2+ and Cu2+. The formation of complexes which separated as precipitates from the reaction mixtures was confirmed by elemental and spectral analyses. The thermal stability of the complexes was evaluated by thermogravimetry.

Kinetic Studies and Mechanism of Hydrogen Peroxide Catalytic Decomposition by Cu(II) Complexes with Polyelectrolytes Derived from L-Alanine and Glycylglycine

The catalytic decomposition of hydrogen peroxide by Cu(II) complexes with polymers bearing L-alanine (PAla) and glycylglycine (PGlygly) in their side chain was studied in alkaline aqueous media. The reactions were of pseudo-first order with respect to [H₂O₂] and [L-Cu(II)] (L stands for PAla or PGlygly) and the reaction rate was increased with pH increase. The energies of activation for the reactions were determined at pH 8.8, in a temperature range of 293–308 K. A suitable mechanism is proposed to account for the kinetic data, which involves the Cu(II)/Cu(I) redox pair, as has been demonstrated by ESR spectroscopy. The trend in catalytic efficiency is in the order PGlygly>PAla, due to differences in modes of complexation and in the conformation of the macromolecular ligands.

The use of polyethyleneglycolmethacrylate-co-vinylimidazole (PEGMA-co-VI) microspheres for the removal of nickel(II) and chromium(VI) ions

The polyethyleneglycolmethacrylate-co-vinylimidazole (PEGMA-VI) copolymers, that can be used in heavy metal removal applications, were synthesized and characterized; and their use as sorbents in heavy metal removal was investigated. It was determined that the ligand vinylimidazole was successfully inserted into the polymer structure. Then, chromium (Cr(VI)) and nickel (Ni(II)) ions were used as model species to investigate the usability of the obtained microspheres in heavy metal removal. The effects of pH of the adsorption medium, initial concentration of the metal ions and VI content of PEGMA-VI microspheres were investigated as the effective parameters on the adsorption capacities of the microspheres. The adsorption rate of the microspheres was also investigated for determination of the optimum adsorption time which is the required time for maximum adsorption capacity. The adsorption capacities under optimum conditions were also determined. The order of adsorption affinities of PEGMA-VI microspheres with respect to the used metals was determined by competitive adsorption studies. According to the obtained results, the highest adsorption affinity of the PEGMA-VI microspheres was towards Cr(VI) ions, the adsorption affinity was less for Ni(II) and the least affinity was towards Cu(II) ions. The adsorption-desorption studies showed that the microspheres were reusable without a significant decrease in the ion adsorption capacities.

Polysilane–Metal Complexes for Organic Semiconductors

New polysilane-metal complexes structures were obtained by the polycondensation reaction of α,ω-bis(chloromethyl)-polymethylphenylsilane with the Ni (II) complex of bis(salicylidene)ethylenedia-mine (salen). The chloro-functionalized polysilane was obtained by a modified Wurtz coupling procedure at low temperatures. To obtain the polymer-metal complex the resulted macroligand was complexed with metal cations. This structure is characterized by a highly localized electroactivitry in the redox moiety combined with a specific σ conjugative effect in the polysilane chain. Infrared, 1H NMR and UV-vis spectral analysis as well as gel permeation chromatography and thermogravimetric analysis were used to investigate the new chemical structures.

Nanoconstructions based on double-stranded nucleic acids

We describe the formation and properties of nanoconstruction that consists of the double-stranded DNA molecules located at distance of 35-50 A in the spatial structure of particles of their cholesteric liquid-crystalline dispersions and cross-linked by artificial nanobridges. The resulting nanostructures possess the peculiar spatial and optical properties.