Biomimetic condensation copolyesters

Copolyterephthalates of bis(4-hydroxy-3-methylphenyl)-2,2-propane and N-methyldiethanolamine and their hydrochloric salts of various compositions and microstructures have been prepared by the copolycondensation of hydrophilic and hydrophobic comonomers. It has been shown that the transition from random proteinlike structures to the block structures makes it possible to preserve biomimetic properties of the copolymers at a smaller content of charged units in macromolecules. The ability of charged polymers to survive in aqueous solutions has been used for the synthesis of copolyterephthalate of N-bis(hydroxyethyl)tetradecylmethylammonium bromide and N-methyldiethanolamine demonstrating fungicidal activity.     

Core-shell nanostructures from single poly(N-vinylcaprolactam) macromolecules: stabilization and visualization

Formation of core-shell poly(N-vinylcaprolactam) (PVCL) single-molecule nanostructures due to interaction of PVCL with metal ions was studied using transmission electron microscopy, 13C NMR, and light scattering. This study demonstrates that addition of CoCl2 to PVCL in its globular conformation yields unimolecular core-shell polymer particles with the core decorated with Co(II) ions. The crucial condition for formation of well-defined unimolecular nanostructures is the presence of stable globular aggregates in aqueous solution. Moreover, the metal ions should have a sufficiently high coordination number (higher than 2) to provide a cross-linking and stabilization of the core.     

Rheological properties of solutions and gels of combined systems hydrophobically modified polyacrylamides-new viscoelastic cationic surfactants

The rheological properties (viscosity and dynamic elasticity modulus) of solutions and gels of combined systems composed of hydrophobically modified polymers containing main-chain charged groups or lacking these groups and of newly synthesized viscoelastic cationic surfactants with different amounts of OH groups and long nonpolar saturated and trans monounsaturated radicals have been studied. It has been shown that the maximum viscosity of solutions of polymer-surfactant complexes corresponds to the very low concentration of the surfactant. Regions where homogeneous and heterogeneous combined solutions and gels exist are considered. An increase in the viscosity of the combined solutions with temperature is discovered and discussed. The synergistic effect of polymers and surfactants is demonstrated, and a more efficient role of surfactants in the case of uncharged polymers is revealed. The roles of the number of OH groups and the length of the nonpolar radical in a surfactant molecule and a difference in the properties of systems containing surfactants with saturated and unsaturated radicals are considered.     

Viscoelastic Properties of Aqueous Anionic Surfactant (Potassium Oleate) Solutions

The dependence of the viscosity of potassium oleate salt-containing solutions on the surfactant concentration is studied. The potassium oleate concentration corresponding to the formation of semidilute solution of cylindrical micelles is determined. It is shown that, in the semidilute regime, one can distinguish two regions characterized by different exponential dependences of the viscosity on the surfactant concentration. The first region corresponds to unbreakable micelle chains that have no time to be destroyed during the characteristic time of reptation, whereas the second region corresponds to “living chains” whose lifetime is shorter than the characteristic time of reptation. In the second region, rheological properties of semidilute potassium oleate solutions are adequately described by the Maxwell model with a single relaxation time.     

Stoichiometric polyelectrolyte complexes as comb copolymers

The collapse behavior of a single comblike copolymer chain has been studied by Monte Carlo simulations. It has been supposed that the solvent is good for the side chains but the solvent quality for the backbone chain changes. It has been shown that depending on the structural parameters of the comb copolymer (the lengths of the backbone and side chains, grafting density of the side chains) various thermodynamically stable morphologies of the collapsed backbone chain can be realized. In addition to ordinary spherical globule we have observed elongated structures as well as necklace-like conformations. The proposed model can be used to describe conformational behavior of stoichiometric complexes between block copolymers with a polyelectrolyte short block and oppositely charged linear homopolymers.     

Uv Dye Lasers

The moat important property of visible dye lasere, that is continuous wave length tuning, stimulated the search for dyes capable to lase UV. And they were founed in 1668¹. Now the need In tunable UV laeers for applications in spectroacopy, photochemistry, isotope separation, remote air and sea probing, etc. ie only more clearly Been. The object of thie paper is to review shortly some recent advances In UV dye lasers.     

Comparison of the accuracy of approximate methods TrESP and TrCAMM for evaluation of pigment coupling in light-harvesting complexes

Due to the large size of light-harvesting complexes, approximate methods are commonly used for calculating the coupling energies between their constituents. Two approximate methods are studied in this work: TrESP and the recently suggested TrCAMM method, based on the expansion of the one-particle density matrix. The quality of approximation of the electrostatic potential in the framework of these two approaches has been compared for two biological pigments as an example—chlorophyll a and bacteriochlorophyll a. It has been shown that both approaches provide high accuracy of approximation of the matrix elements of the electrostatic potential operator. In addition, it has been demonstrated that symmetrization of the one-particle density matrix in the framework of the TrCAMM method significantly improves the calculation accuracy and makes the computational procedure unambiguous.     

Dynamics of Gold Ablation into Water

Using the gold–water pair as an example, we analyze the problems related to an ultrashort laser action on a metallic target submerged in a transparent liquid.