Polymer Science, Series C最新文献

Nanomechanical properties and, in particular, the bending rigidity of natural and artifficial nanomembranes can be strongly affected by anchored or tethered macromolecules. We present the theory of the induced bending rigidity of polymer brushes symmetrically tethered to both surfaces of the membrane and immersed into the solvent. In contrast to previous works the finite thickness of the membrane was taken into account. The analytical and numerical variants of the self-consistent field approach were used. The mean and Gaussian Helfrich’s bending moduli as functions of the polymerization degree, branching parameter and grafting density of tethered macromolecules were determined both for good and theta solvent conditions. It was shown that the absolute values of the Helfrich’s bending moduli increase with the membrane thickness. The increase of the thickness leads also to the change of the relation between moduli for branched and linear brushes at the same polymerization degree and grafting density. For thin membranes the bending moduli for brushes with linear chains exceed those for branched brushes. However by an increase of the «bare» membrane thickness the moduli for brushes with branched macromolecules can become equal and even exceed those for brushes consisting of their linear analogs.

Features of ionic ring-opening polymerization for preparing star-shaped polymers are considered. The possibilities of controlled synthesis of star-shaped structures using cyclic monomers of various classes are demonstrated. Data on the preparation of star polymers using the approaches of “grafting from” a multifunctional initiator, “grafting through” a macromonomer, and “grafting to” a multifunctional coupling agent are systematized and summarized.

Amphiphilic sulfo- or amino-containing molecular brushes are synthesized by the radical copolymerization of methacrylic esters containing oligo(ethylene glycol) and/or oligo(propylene glycol) blocks of varying length and arrangement with 2-acrylamido-2-methylpropanesulfonic acid or N-(3-dimethylaminopropyl)methacrylamide in solutions (water, ethyl acetate, toluene). In copolymerization with 2-acrylamido-2-methylpropanesulfonic acid in water, the compositional homogeneity of the copolymers grows appreciably with increasing concentration of initial solutions. It is shown that the structure of macromonomers has almost no effect on their reactivity ratios in copolymerization with N-(3-dimethylaminopropyl)methacrylamide in organic solvents. The synthesized amino-containing molecular brushes exhibit stimuli-responsive properties in aqueous solutions, and the arrangement of hydrophilic and hydrophobic blocks in the side chains of macromolecules affects dependences of the phase transition temperature on polymer concentration and рН.

The reports on the synthesis and study of polycarboranesiloxanes published after 2000 have been reviewed. The data on the C- and B-substitution at the carborane core are presented. Major parameters of the synthesized polymers, including thermal, mechanical, and others) have been estimated.

New procedures for the preparation of grafted and branched amphiphilic copolymers based on poly(ethylene glycol) have been suggested. Radical polymerization with TEMPO and sulfuric acid has afforded controlled synthesis of grafted copolymers of methyl methacrylate with poly(ethylene glycol) methacrylate. Radical copolymerization of allyl acetate with poly(ethylene glycol) acrylate in the presence of divinylbenzene has given branched copolymers. It has been shown that these copolymers can form micelles in aqueous medium; cytotoxicity of the copolymers and the ability to suppress the resistance of human cancer cells NCI/ADR-RES have been investigated.

The behavior of a single linear chain inserted in a planar polymer brush made of second-generation dendrons grafted via their focal point has been theoretically studied using the Scheutjens–Fleer self-consistent field method. It has been shown that the linear macromolecule can undergo a conformational transition from the state of a “coil” located inside the brush to the state of a “flower” consisting of a strongly stretched stem immersed in the brush and a head located above the brush. This transition has features of a first-order phase transition. It can be provoked by increasing the length of the linear macromolecule, by increasing the grafting density, or by improving the quality of the solvent in which the brush is immersed. An increase the linear chain length lowers the height of the energy barrier separating the “coil” and “flower” states, but the transition itself occurs in a solvent of poorer quality. A new state of the linear chain under the poor solvent conditions, “flower in the brush,” when both the stem and the head of the flower are inside the brush, was discovered.

Polyvinylidene fluoride copolymers with grafted polyethyl methacrylate chains have been synthesized for the first time via photoinduced reversible deactivation radical polymerization. Binary and ternary copolymers of vinylidene fluoride with chlorotrifluoroethylene and trifluoroethylene were used as initial polymer chains for modification. The effect of the content of grafted chains on the thermal and dielectric properties of the copolymers has been studied. It has been shown that an increase in the content of grafted chains leads to a decrease in the degradation temperature, dielectric permittivity, and dielectric losses of the copolymers, but it significantly improves their film-forming properties due to a decrease in the degree of crystallinity.

This review addresses the systematization and analysis of methods for the synthesis of ferrocenyl-containing oligo- and (co)polysiloxanes and the potential application areas of these compounds. Various ways to introduce a ferrocenyl moiety into the structure of oligo- and (co)polysiloxanes are considered. Methods of synthesizing ferrocenyl-containing oligo-, cyclo-, silsesquio-, and (co)polysiloxanes via the reactions of catalytic hydrosilylation, dehydrocoupling, azide-alkyne cycloaddition, hydrothiolation, and ring-opening polymerization and polycondensation are demonstrated. It is shown that ferrocenyl-containing oligo- and (co)polysiloxanes feature the redox behavior and are of interest for molecular electronics, chemical modification of electrodes, and design of electrochemical sensors, and as materials for charge dissipation and neuronal implants. Oligo- and (co)polysiloxanes with chiral ferrocenyl substituents can be used in asymmetric catalysis and manufacture of liquid crystals for nonlinear optical systems.

Graft copolymers with the polyfluorene backbone and poly(tert-butyl methacrylate) and poly(methacrylic acid) side chains are synthesized by atom transfer radical polymerization. The behavior of the synthesized brushes in chloroform, ethanol, and water solutions is studied by molecular hydrodynamics and optics. The graft copolymers are characterized by a high grafting density. The brushes with poly(methacrylic acid) side chains form unimolecular micelles capable of encapsulating curcumin in aqueous solutions. The grafting density of side chain affects the properties of brush complexes with curcumin.