Polymer Science, Series C最新文献

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.

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.