Polymer Science, Series C最新文献

The history and prospects for the development of interatomic interaction potentials for the simulation of molecular systems and, in particular, polysaccharides are presented. Popular families of potentials, such as CHARMM, GROMOS, AMBER, and OPLS, are considered. Problems that limit the applicability of these models to sugar monomers have been recognized, which are poor reproducibility of experimentally determined properties and hyperaggregation at low concentrations. The development vectors of this area are also considered: the modification of nonbonded interactions and the use of polarizable potentials. Applications of the atomistic simulation of polysaccharides in actual fundamental and industrial problems are demonstrated using the example of cellulose. Important computational works are presented that have made a significant contribution to the understanding of the structure and processes occurring in a cellulose crystal. In addition, an overview is given of the currently available time scales and characteristic sizes of systems for simulation in the GROMACS, LAMMPS, OpenMM, and AMBER packages for the sucrose solution model.

Effect of the architecture and composition of a hydrophilic microgel catalyst on the rate of interfacial catalytic reaction proceeding at the water/oil interface and involving reagents dissolved in opposite phases is studied using dissipative particle dynamics simulations. It is shown that a decrease in the crosslinking density of the microgel, the existence of a cavity in its architecture, an increase in its size, the incorporation the hydrophobic comonomers into a macromolecule, and a rise in the degree of solubility of a network macromolecule in oil contribute to acceleration of the catalytic reaction due to increase of the area of the water–oil–microgel contact and growth of the number of contacts between reagents and catalytic groups. However, in the case of amphiphilic microgels and microgels soluble in both phases, the acceleration of the reaction is restrained by a low rate of reagents diffusion and a rapid reduction in the concentration of reagents in the vicinity of catalytic sites.

Three monosilicon-substituted norbornene monomers with phenyl and siloxane groups at the silicon atom are synthesized by the one-step hydrosilylation of 2,5-norbornadiene. The proposed method allows the synthesis of monomers with a higher content of polymerization-reactive exo-isomer in products compared with similar adducts formed by the Diels‒Аlder reaction. The synthesized monomers show high reactivity in both metathesis polymerization and addition polymerization more sensitive to the substituent volume. Using these monomers two series of high molecular weight silicon-substituted polynorbornenes are prepared which are found to be glassy and thermally stable polymers.

The main models of phantom and topologically entangled polymer networks are surveyed. A theory of anisotropic and nonaffine deformation of both swollen and deswollen (with partial solvent removal) strongly entangled polymer networks in athermal and θ-solvents has been developed. It is shown that under weak anisotropic deformations of the deswollen network, the entanglement tube consists of fractal loopy globules. In a θ-solvent, slight deformations of the network lead to a decrease in the overlap of loopy globules without changing their sizes. Deformations of swollen networks, as well as strong deformations of deswollen networks, are described in terms of the slip-tube model. An effective Hamiltonian has been derived that determines the entropy of fractal loopy globules. Based on the Hamiltonian, it is shown that topological constraints can be described using the polymer–quantum diffusion analogy. The connection between topological and quantum entanglements is demonstrated.

A synthetic scheme allowing the preparation of nanostructured organosilicon luminophores of branched or dendritic structure with up to 18 bithiophenesilane donor fragments and one central acceptor fragment has been elaborated. This universal scheme has been successfully upscaled to 20 g of the product, and its efficiency has been verified by the synthesis of two earlier unknown bithiophenesilane dendrimers with dense molecular shell and the central acceptor fragment, 1,4-bis(5-phenylthienyl-2-yl)benzene. The synthesis of more branched dendrimers under the Suzuki reaction conditions has led to the formation of the side products with the rupture of the Si–C(thiophene) bond, not typical of the synthesis of analogous compounds with lower branching degree under the same conditions.

Theoretical results of the authors in the field of the capillary thinning of polymer solution threads are reviewed. The dynamics of threads of both concentrated solutions without entanglements and dilute solutions, where hydrodynamic interactions play an important role, is considered. A molecular approach, in which macromolecules are simulated by a semiflexible chain, is used as a basis. This makes it possible to describe, from common positions, the nonlinear elasticity of solution and interactions taking into account the orientation of the chains. Particular attention is given to thread thinning in the region of the elastic behavior of solution where macromolecules unfold along the axis of stretching. The results of analysis of the capillary stability of a thread and conditions for solvent droplets emergence on its surface are presented, and the dynamics of formation of the hierarchical structure of beads-on-string droplets is viewed. Mechanisms behind the subsequent merging of droplets related to solvent overflow and droplets diffusion along the polymer string are discussed. The polymer string breakup occurs at time scales higher than the Rouse relaxation time of the polymer chain. String hardening and fiber formation may be an alternative.

The contribution of I.Ya. Erukhimovich (1947–2022) to the creation of the theory of microphase separation in di- and triblock copolymers has been briefly analyzed. His matrix method of calculating correlation functions for multicomponent polymer systems has been applied to find the spinodal of a diblock copolymer melt in a static electric field. It has been strictly shown that for a linear dependence of local dielectric constant of the copolymer on the order parameter the spinodal condition remains the same as in the absence of the electric field. The correction to the critical value of the Flory‒Huggins parameter has been calculated for more general case of the quadratic dependence.

This review analyzes the areas of practical application of oligomeric and polymeric organometal siloxanes as reduced fire risk coatings, antifriction and heat-resistant coatings, materials with high refractive index, and protective coatings for space equipment as well as functional branched oligomers as the most universal organometal siloxane synthons for diverse use.