Polymer Science, Series C最新文献

The interaction of phenylboronic acid with polyphenylsiloxane and a hydroxy(phenyl)siloxane oligomer has been studied. For the first time, phenylboronic acid was used as a starting material for the production of polyboronphenylsiloxanes under conditions of mechanochemical activation. It has been established that the main side processes induced by activation are abstraction of the phenyl substituent from the boron atom, formation of biphenyl, and trimerization of phenylboronic acid. Since boron compounds (including phenylboronic acid) have biological activity, their introduction into the polymer chain will make it possible to obtain materials with useful properties. For example, boron-containing polymers can be used as coatings to protect against insect vectors of various diseases. The work is fundamental in nature and contributes to revealing and understanding the mechanisms of mechanochemical modification of organosilicon polymers.

Crosslinked polysiloxanes with boron bis(dibenzoylmethanate) complexes used as crosslink junctions of polymer networks are first synthesized, and their physicochemical, mechanical, thermal, and fluorescent properties are studied. It is shown that the polymers under study feature the elastic behavior, possess high thermal and thermo-oxidative stability, and exhibit intense fluorescence in a wide wavelength range (400‒700 nm).

Carboxyl-containing aryloxycyclotriphosphazene (I) has been used for curing the ED-20 epoxy resin or a phosphazene-containing epoxy oligomer. In the case of ED-20, curing occurs in the range of 125‒220°C and is accompanied by an exothermic effect that increases from 26 to 50 J/g with an increase in the amount of aryloxycyclotriphosphazene (I) from 25 to 50%. The curing of the phosphazene-containing epoxy oligomer occurs in the temperature range of 140–240°C and is accompanied by an endothermic effect (−ΔH = 6.5–6.8 J/g). Cured compositions based on ED-20 + I are self-extinguishing (flammability class V‑1 according to UL-94), and phosphazene-containing epoxy oligomer + I compositions are noncombustible (class V-0 according to UL-94) regardless of the ratio of the initial components.

The self-organization of biocompatible amphiphilic block copolymers of D,L-lactide and ethylene oxide with various hydrophobic poly(D,L-lactide) block length in aqueous media has been investigated. It has been shown that the nature of nonselective organic solvent has a considerable effect on the size, size polydispersity, and morphology of micelles of a block copolymer with a long poly(D,L-lactide) block. To elucidate the dependence of properties of block copolymer micelles on the common organic solvent type (acetone, tetrahydrofuran, N,N-dimethylformamide, and acetonitrile) various parameters of the used solvents have been estimated, and correlation between the Flory–Huggins coefficient and the surface tension between the hydrophobic block and the nonselective organic solvent and the parameters of micellar structures has been found.

Solutions based on polymer-like micelles of ionic surfactants attract the attention of scientists as stimuli-responsive systems that can transform from a low-viscosity Newtonian fluid to a viscoelastic solution having a viscosity of up to 10 kPa s and an elastic response. The shape of micelles and their length are determined by the balance of hydrophobic and electrostatic interactions; therefore, the use of various low molecular weight substances or functional nanoparticles as additives can significantly change the rheological properties of such solutions and impart new stimuli-responsive properties to them. This review presents the most commonly used methods for controlling the properties of multicomponent solutions of wormlike surfactant micelles, including nanocomposite systems. Modern areas of practical application of such systems and prospects for their development are described.

We utilize the self-consistent field theory to explore the mechanical and electrical properties of charged surfaces immersed in polyelectrolyte solutions that could be potentially useful for electrochemical applications. Our research focuses on how the dielectric heterogeneity of the solution could affect the disjoining pressure and differential capacitance of the electric double layer. Relying on the developed theoretical framework, based on the Noether’s theorem, we calculate the stress tensor, containing the term, arising from the conformational entropy of the polymer chains. With its help we compute the disjoining pressure in polyelectrolyte solution confined between two parallel charged surfaces and analyze its behavior as a function of separation between the surfaces for different values of dielectric mismatch parameter. We also calculate the differential capacitance of the electric double layer and discuss how dielectric heterogeneity of the polyelectrolyte solution influences its values.

The adsorption of a single random copolymer chain containing correlations in a sequence on the chemically heterogeneous periodic surface with the alternating striped texture is studied theoretically. The problem is solved within the framework of a partially directed walk polymer model in three dimensions using the generating functions approach and the annealed disorder approximation for averaging over the ensemble of random sequences of units in the copolymer. Dependences of the adsorption transition point on the composition of the random copolymer and the degree of correlation in the random sequence of units for various periodic surfaces are presented. It is shown that for compositionally symmetric and weakly symmetric surfaces there is the optimal composition of the random copolymer and the degree of correlation in the sequence of units, at which the inverse temperature corresponding to the adsorption transition point has a local minimum. In the case of the compositionally symmetric surface, the “optimal” random copolymer is also symmetric in composition. For surfaces with a pronounced composition asymmetry the best adsorbent is a homopolymer complementary to sites that prevail on the surface. The degree of asymmetry range, in which the dependence of the inverse transition temperature on the copolymer composition and the correlation parameter exhibits the local minimum, is fairly narrow.

Some rod structures consisting of tetrahedral atoms and differing in symmetry are considered. The structures are obtained as a stereographic projection of polytope 240 vertices into three-dimensional Euclidean space when the polytope rolls along a straight line belonging to this space. The axes of the rod structures are the projections of great circles of a three-dimensional sphere containing the polytope 240 vertices. It has been shown that the rod structures obtained earlier by modular design are topologically equivalent to those considered in this paper, but they have a changed symmetry. Three possible conformations following from the results of this work are presented for a C_nH_2n hydrocarbon chain with close packing of atoms, conservation of the tetrahedral coordination of carbon atoms, and noncrystallographic symmetry.

The self-assembly of amphiphilic homopolymers tightly grafted to the spherical nanoparticle and immersed in a selective solvent is studied by the computer experiment method. Conditions under which macromolecules form thin membrane-like layers surrounding the nanoparticle are determined. It is first shown that the emerging polymer structures may be approximated by complete embedded minimal surfaces satisfying the Weierstrass representation, namely, helicoid, catenoid, and Enneper and Costa surfaces. Mathematical constructions defining these minimal surfaces highlight a new type of ordering of polymer structures and determine its symmetry classification similar to crystal classification by Fedorov groups. Calculations for the two considered sets of parameters show that structures approximated by a helicoid are energetically more favorable than structures approximated by other minimal surfaces.