The effect of silver nanoparticles on the phase state of comb-shaped liquid crystalline polymers with cyanobiphenyl mesogenic groups

A new approach is proposed for the preparation of a new class of hybrid polymer systems based on comb-shaped LC polymers with cyanobiphenyl mesogenic groups and silver nanoparticles with dimensions ranging from 5 to 54 nm. A correlation between copolymer composition and dimensions of the formed nanoparticles is established. As the concentration of nanoparticles in LC copolymer is increased, the resultant glass transition temperature increases, and the temperature interval of the existence of LC phase is reduced. This behavior is related to the adsorption of cyanobiphenyl and carboxylic polymer groups on the surface of silver nanoparticles. In this case, the conductivity and dielectric permittivity of the composites are also increased.     

Reversible temperature-induced transformations of poly(N-ethyl-4-vinylpyridinium) complexes with dodecyl sulfate in aqueous salt solutions

Supramolecular organization of complexes formed by poly(N-ethyl-4-vinylpyridinium bromide) and sodium dodecylsulfate in aqueous salt solutions was studied as a function of temperature and concentration of the complexes. It was shown that a decrease in temperature and/or concentration of complexes led to their reversible disaggregation into a molecularly dispersed (“unipolymer”) state. The ratio between the components in complex particles remained unchanged in this case. It was first found that phase separation in aqueous solutions of the complexes upon temperature elevation is accompanied by the precipitation of a nonstoichiometric complex.     

Radio-frequency superradiance induced by the rheological explosion of polymer composites containing paramagnetic cobalt complexes

Superradiance induced by the rheological explosion of composites based on polystyrene, cobalt acetylacetonate, and/or 3,5-di-tert-butylcatechol has been investigated. The superradiance intensity is determined by solid-phase chemical reactions induced by the rheological explosion. EPR, X-ray diffraction, and electron microscopic characterization of stable products resulting from the rheological explosion in the polymer matrix has demonstrated that the superradiance intensity is related to the electronic properties and structure of two-spin intermediates, namely, radical pairs and organoelement biradicals.     

Self-assembly phenomena in multicomponent systems composed of polyelectrolytes and ionic surfactants

The ability of anionic surfactants to expel fluorescencetagged poly(methacrylate) polyanion ( PMA ^*) from nonstoichiometric water-soluble interpolyelectrolyte complex ( NIPEC ) formed by PMA^* and polycation-quencher poly(N-alkyl-4-vinylpyridinium) ( PAlkVP ) and to form polyelectrolyte-surfactant complex ( PESC ): NIPEC(PMA^*-PAlkVP)+surfactant ⇔ PESC(PAlkVP-surfactant)+PMA^* was revealed and studied by fluorescence quenching technique and high-speed sedimentation. It was found that the transfer of poly(N-ethyl-4-vinylpyridinium) from NIPEC to PESC proceeded up to complete conversion providing a self-assembly of both PESC and NIPEC particles in the course of the reaction. The concentration of the surfactant and the “tail” length of the surfactant molecule, as well as the structure of Alk groups, temperature, pH, ionic strength, and the nature of added low-molecular-weight electrolyte proved to be the factors of the reaction equilibrium control.     

Self-assembly of ionogenic surfactants during their interaction with poly(propylenimine) dendrimers

The structure of complexes formed by poly(propylenimine) dendrimers of five generations and anionic micelle-forming surfactants is studied by X-ray diffraction. It is shown that, in complexes of lower generation dendrimers, the lamellar packing of surfactants is dominant. In complexes formed by dendrimers of the fourth and fifth generations, packing typical of compact dendrimer molecules prevails. This packing can be attributed to the distorted dense packing of ball-like complex species. Structural models of complexes that allow for penetration of surfactants into the dendrimer molecule and the size ratio of the aliphatic radical of a surfactant and a dendrimer are advanced.     

Spontaneous Assembly of Miktoarm Stars into Vesicular Interpolyelectrolyte Complexes

Mixing a bis‐hydrophilic, cationic miktoarm star polymer with a linear polyanion leads to the formation of unilamellar polymersomes, which consist of an interpolyelectrolyte complex (IPEC) wall sandwiched between poly(ethylene oxide) brushes. The experimental finding of this rare IPEC morphology is rationalized theoretically: the star architecture forces the assembly into a vesicular shape due to the high entropic penalty for stretching of the insoluble arms in non‐planar morphologies. The transmission electron microscopy of vitrified samples (cryogenic TEM) is compared with the samples at ambient conditions (in situ TEM), giving one of the first TEM reports on soft matter in its pristine environment.

     

Radiation-Chemical Reduction of Copper Ions in Nanoporous Matrices Based on High-Density Polyethylene

Russian Journal of General Chemistry - The effect of preliminary annealing of semicrsytalline high-density polyethylene films on the parameters of nanoporous structure formed during deformation of...