Polymer Science, Series C最新文献

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.

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.

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.

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.

The aqueous solutions of star-shaped four-arm poly(2-alkyl-2-oxazolines) and poly(2-alkyl-2-oxazines), in which the upper rim-functionalized calix[4]arene acts as a branching center, are studied by static and dynamic light scattering and turbidimetry. It is shown that at low temperatures in aqueous solutions of these polymer stars aggregates are formed as a result of interaction of hydrophobic calix[4]arene cores and formation of hydrogen bonds between dehydrated monomer units of arms. The process of aggregation dominates upon heating of the solutions. Varying the mode of arm attachment to a core causes a change in its configuration. The values of the phase transition temperature decrease when comparing polymers with the lower rim-functionalized core with polymers in which arms are attached to the upper rim of calix[4]arene.

Aqueous solutions of linear poly(2-ethyl-5,6-dihydrooxazine) and eight-armed star-shaped poly(2-isopropyl-2-oxazoline) have been studied by light scattering and turbidimetry. The influence of the duration of annealing at temperatures above the phase separation temperature on the behavior of the solutions has been analyzed. It has been shown that the characteristics of linear polymer solutions do not vary in the studied annealing time interval. The cloud point of star polymer solutions also does not depend on the annealing time. However, significant changes have been observed at the microscopic level, namely, irreversible aggregation due to the interaction of hydrophobic segments of poly(2-isopropyl-2-oxazoline) arms formed during annealing at a high temperature.

This review addresses recent achievements in the field of producing photonic-crystalline structures from polymer core/shell particles. The synthesis of polymer particles, in which a core is formed by hard crosslinked polymers and a shell is based on thermoplastic polymers or elastomers, offers the way to create the so-called stimuli-responsive (or “smart”) photonic crystals. Main principles underlying the self-assembly of polymer particles into periodic colloidal structures are considered. Elastic large-area 3D structures can be formed by the self-organization of core/shell particles under their compression at high temperatures. Prospects for the application of smart photonic-crystalline films are also highlighted.

Studies on free-radical micellar polymerization of ionogenic amphiphilic monomers have been analyzed. Major types of the monomers and features of their polymerization in the micellar state have been described. Approaches to the analysis of kinetic features and mechanism of micellar polymerization have been considered; the applicability of the Morgan–Kaler microemulsion model to the description of quantitative features of micellar polymerization has been shown.

New amphiphilic ABA-type molecular brushes of mixed block–graft topology, where the central block B is a molecular brush with a hydrophobic polyimide backbone and hydrophilic side chains of poly(methacrylic acid) and A blocks are peripheral hydrophobic chains of poly(methyl methacrylate), have been synthesized. For the synthesis of the copolymers, an approach based on a combination of atom transfer radical polymerization (ATRP) and click chemistry in the variant of Cu(I)-catalyzed azide–alkyne cycloaddition was proposed. To implement the proposed approach, a procedure was developed for the synthesis of heterofunctional polyimide macroinitiators containing ATRP-initiating groups in each unit and terminal alkynyl groups capable of participating in the “click” reaction. Further, the synthesis of well-defined block–graft ABA molecular brushes was carried out using such initiators. First, peripheral poly(methyl methacrylate) chains were synthesized in a controlled mode using ATRP, followed by their functionalization with azide groups. Then, using the click chemistry approach, these chains were grafted to the terminal alkynyl groups of the heterofunctional initiator. The hydrophilic side chains were introduced into block B using the “grafting from” ATRP method in several steps through the intermediate formation of a regularly grafted prepolymer with poly(tert-butyl methacrylate) side chains. At the last step, as a result of selective acid hydrolysis of the side-chain ester groups in block B, amphiphilic multicomponent brushes with hydrophilic poly(methacrylic acid) units in the side chains were obtained. The possibility of sequential and simultaneous ATRP and click reaction has been examined.