Statics and Dynamics of the “Liquid-” and “Solidlike” Degrees of Freedom in Lightly Cross-Linked Polymer Networks

The density-density correlation function, that determines the angular dependence of the scattering intensity, is calculated for strongly deformed, lightly cross-linked polymer networks. The replica variant of the tube model is used to take into account the entanglement effects. It is shown that the contribution of thermally driven (annealed) density fluctuations to this correlation function is small with respect to the contribution of frozen-in (quenched) fluctuations. We also calculate the free energy functional for such “soft” solids, taking into account liquid- as well as solid-like degrees of freedom at different spatial scales. The dynamics of the “abnormal butterfly effect” is theoretically studied

Stiffness and conformations of molecular bottle-brushes strongly adsorbed on a flat surface

A theory of the conformational behavior and analysis of the persistence length of molecular bottle-brushes strongly adsorbed on a flat surface in a good solvent is presented. For long enough side chains we have shown that the adsorption of a small fraction of side chains already leads to significant increase of the stiffness and drastic conformational changes of the brush in comparison with the 3D case. For a symmetrical distribution of the adsorbed side chains with respect to the backbone, the equilibrium conformation of the brush is close to a rod-like one due to the very large stiffness of the molecule. Under certain conditions the excluded-volume interactions of the side chains of an asymmetrical brush can lead to its bending or twisting in spiral. The obtained results are in good agreement with computer simulations

Synthesis of acrylic acid and acrylic esters via oxidation and oxidative alkoxylation of acrolein under mild conditions with selenium-modified microgel catalysts

Systematic studies of acrolein oxidation and oxidative alkoxylation catalyzed by Se-modified microgel catalysts under mild reaction conditions were conducted. Se-modified microgels proved to be highly active colloidal catalysts and exhibited high performance for the oxidation of acrolein to acrylic acid and oxidative alkoxylation to the corresponding methyl/ethyl/butyl acrylates using hydrogen peroxide as a green oxidant. Methyl acrylate or acrylic acid can be synthesized in high yield (89-91%) and with high selectivity (97-99%) simply by regulating the solvent type and the concentration of selenium moieties in the microgel structure. Se-microgels exhibit exceptional catalytic activity compared with other Se-containing molecules of organic and inorganic nature. Due to the unique properties of the microgels that combine advantages from homogeneous and heterogeneous catalytic systems in terms of activity and selectivity as well as re-use possibilities, Se-microgel catalysts can be easily separated and reused in several catalytic cycles and remain highly active