TG and DSC studies of filled porous copolymers

A complex approach including thermogravimetry, differential thermal analysis and differential scanning calorimetry was applied to study characteristics of non-filled and filled porous copolymers of divinylbenzene with styrene or some acrylic monomers: di(methacryloyloxymethyl)naphthalene, methacrylic ester of p,p’-dihydroxydiphenylpropane diglycidyl ether, and dimethacrylglycolethylene. High disperse silicas with the grafted methyl and silicon hydride groups in the surface layer were used as fillers. The kinetic parameters of thermal degradation for composites obtained were determined by different methods.     

Influence of Solution Acidity on Structure of Actinocin Derivatives and Their Affinity to DNA Studied as a Function of pH by Raman Spectroscopy

An important problem of molecular biophysics is the influence of pH and ionic strength of a solution on chemical structures and charge of biologically active substances. By means of pH titration and Raman spectroscopy methods, the influence of solution acidity on structural changes of actinocin derivatives was investigated, analogues to antitumor antibiotic actinomycin D. It has been shown that these ligands have different values of cation charges in neutral solutions. From analysis of Raman spectra, it was concluded that protonation of nitrogen atom and amino group of the phenoxazone ring starts only at pH < 3.5. It was shown that protonation of actinocin derivative with two amide groups (diaminoactinocin) occurred in two steps. Corresponding protonation constants for diaminoactinocin (log k ₁ = 6.9 ± 0.5 and log k ₂ = 5.3 ± 0.1) and for partially protonated actinocin derivative with three methylene groups in the side chains (log k = 5.3 ± 0.1) were obtained. Characteristic frequencies of Raman spectra for the basic functional C=O, C2–NH₂, C–C=C, and –N=C groups of phenoxazone chromophore of actinocin derivatives in protonated and nonprotonated states were determined. The different affinities of binding of variously charged ligands to DNA have also been demonstrated.     

Activating charge-transfer state formation in strongly-coupled dimers using DNA scaffolds

Strongly-coupled multichromophoric assemblies orchestrate the absorption, transport, and conversion of photonic energy in natural and synthetic systems. Programming these functionalities involves the production of materials in which chromophore placement is precisely controlled. DNA nanomaterials have emerged as a programmable scaffold that introduces the control necessary to select desired excitonic properties. While the ability to control photophysical processes, such as energy transport, has been established, similar control over photochemical processes, such as interchromophore charge transfer, has not been demonstrated in DNA. In particular, charge transfer requires the presence of close-range interchromophoric interactions, which have a particularly steep distance dependence, but are required for eventual energy conversion. Here, we report a DNA-chromophore platform in which long-range excitonic couplings and short-range charge-transfer couplings can be tailored. Using combinatorial screening, we discovered chromophore geometries that enhance or suppress photochemistry. We combined spectroscopic and computational results to establish the presence of symmetry-breaking charge transfer in DNA-scaffolded squaraines, which had not been previously achieved in these chromophores. Our results demonstrate that the geometric control introduced through the DNA can access otherwise inaccessible processes and program the evolution of excitonic states of molecular chromophores, opening up opportunities for designer photoactive materials for light harvesting and computation.

DNA scaffolds enable the activation and suppression of photochemistry between strongly-coupled synthetic chromophores.     

Thermomechanical properties of polymeric composites based on 2-hydroxyethylmethacrylate and fumed silicas

Summary Thermomechanical properties have been investigated for the composites synthesized by the thermal polymerization of 2-hydroxyethylmethacrylate or its polymerization initiated with acrylamide complex of cobalt nitrate in the presence of the fumed silica or silicon hydride-containing silicas. The effect of the filler surface nature on temperature dependencies of deformability of the polymeric composites has been studied.     

Hydrothermal Synthesis of Mixed Oxide Compositions of Cobalt-Zirconium and their Catalytic Activity in the Decomposition of Hydrogen Peroxide

The article presents the results of research on the hydrothermal synthesis of nanoscale oxide of cobalt and zirconium and their mixed oxide compositions. The synthesized samples have been characterized by the X-ray phase, scanning electron microscopy and nitrogen adsorption-desorption methods; the composition of the samples has been determined by chemical analysis methods, and their catalytic activity in the decomposition of hydrogen peroxide has been studied. It has been shown that during synthesis, highly dispersed cobalt and zirconium oxide are formed, and the sample of the composition (mol %): Co₃O₄(88)−ZrO₂(12) has the highest specific surface area (181.2 m²/g) and the highest activity (K=6.18 ⋅ 10⁻² s⁻¹) against the decomposition of hydrogen peroxide. The increasing of the ZrO₂ content in oxide compositions reduces their catalytic activity. The particle size in the synthesized samples is 7–38 nm.