G. A. Estrina

Synthesis, Structure, and Properties of Branched Polymethacrylates

The methacrylate: branching agent: chain growth regulator optimal ratios that allow the synthesis of branched polymethacrylates via the crosslinking free-radical copolymerization under the regime of conventional or catalytic chain transfer have been estimated. Relationships between the molecular-mass characteristics of the copolymers, their content of intact C=C bonds, the composition of the starting monomer mixture, and the structure of the branching agent and polymer chain growth regulator have been established. The rheological properties of the branched MMA-based copolymers have been studied. It has been shown that the copolymers are characterized by a weaker dependence of reduced viscosity on the polymer concentration in solution than that for the linear PMMA. The diffusion-sorption behavior of the branched polymethacrylates is determined by the content of the branching agent in them.

Kinetics and mechanism of the anionic polymerization of acrylamide monomers

The thermodynamics, kinetics, and mechanism of the anionic polymerization of a number of acrylamide monomers has been studied with the use of isothermal and scanning calorimetry, liquid chromatography, 1H NMR and IR spectroscopy, mass spectrometry, and chemical analysis of functional groups. It has been demonstrated that the polymerization system shows the living character and the interchain exchange reactions are absent. It has been shown that N,N-diethanolacrylamide and N,N-diethanol(meth)acrylamide are uninvolved in anionic polymerization. The causes of this phenomenon have been ascertained. The products of the anionic polymerization of acrylamides are hyperbranched copolymers containing heterochain and carbochain fragments. Macromolecules contain end amide and acrylamide groups; in some macromolecules, end tert-butoxide groups of the used polymerization initiator are detected. For the products of the anionic polymerization of the acrylamide monomers under study, the temperatures of glass transition and melting have been measured.

Control of crosslinking free-radical copolymerization of ethylene glycol dimethacrylate with alkyl methacrylates of various structures and macromolecular design of copolymers

The possibility of controlling the crosslinking free-radical copolymerization of ethylene glycol dimethacrylate with alkyl methacrylates of various structures and of the macromolecular design of the resulting copolymers through the use of small additives of cobalt porphyrin, which terminates polymer chain growth via catalytic chain transfer, has been studied. It has been shown that steric hindrances to the interaction of a propagating radical R* with pendant C=C bonds that are created by bulky substituents of dodecyl methacrylate provide an additional factor that impedes intrachain cyclization and crosslinking reactions that give rise to network structures.

Synthesis, Structure, and Properties of Bifunctional Azobenzene Monomers and Polymers on Their Basis

A new preparative procedure for the synthesis of new bifunctional azo monomers with different ratios of methacryloyl and hydroxyl groups has been developed. The monomers thus prepared contain a nonlinear optical 4′-amino-4-nitroazobenzene group and can be involved in polymerization, polycondensation, and polymer-analogous transformation reactions to afford linear and network polymers. The free-radical copolymerization of 4′-[N-methyl-N-(3-methacryloyloxy-2-hydroxypropyl)]amino-4-nitroazobenzene with methyl methacrylate has been studied with the aim of preparing azobenzene [1+0] prepolymers with pendant chromophore groups, and the reactivity ratios and reactivity factors of the comonomers have been calculated. The hydroxyl-containing copolymers are characterized by rather high molecular mass, satisfactory heat resistance and thermal stability, and good film-forming behavior. These copolymers may be crosslinked with the use of diisocyanates and thus may form thin optically homogeneous red films.

Synthesis of silver nanoparticles with polystyrylcarboxylate ligands

Silver nanoparticles stabilized by polystyrylmonocaboxylate ligands with varied chain lengths are synthesized via the low-temperature reduction of silver polystyrylmonocaboxylate with triethylamine. Silver nanoparticles have small dimensions, narrow size distributions, high stability, and ability to redisperse in nonpolar solvents. The kinetic features of the reaction are studied via high-performance liquid chromatography; UV, visible and IR spectroscopy; and transmission electron microscopy. It is shown that the reduction of silver occurs in the cores of reverse micelle species organized by diphilic macromolecules of silver polystyrylmonocarboxylates.

Synthesis and free-radical polymerization of water-soluble acrylamide monomers

Water-soluble acrylamide monomers N-(hydroxymethyl)acrylamide, N-(hydroxymethyl)methacrylamide, N,N-diethanolacrylamide, N,N-diethanolmethacrylamide, N,N-methylethanolacrylamide, and N,N-methylethanolmethacrylamide have been synthesized and characterized. The kinetics and thermodynamics of the free-radical polymerization of these monomers and of the model compounds N-isopropylacrylamide and acrylamide have been studied by the methods of isothermal and scanning calorimetry. The structure and the solubility of the said polymers in water and organic solvents have been investigated and their molecular-mass characteristics and temperatures of glass transition (T g) and melting (T m) have been examined by DSC, liquid chromatography, 1H NMR and IR spectroscopy, and chemical analysis of functional groups. Hydrogels and amphiphilic network polymers based on acrylamide monomers have been prepared and characterized.

Synthesis of a macromonomer based on ɛ-caprolactone and 2-hydroxyethyl methacrylate

The mechanism of forming the macromonomer based on ɛ-caprolactone and 2-hydroxyethyl methacrylate under the effect of dibutyltin dilaurate has been investigated. The molecular-mass characteristics and the functional-type distribution of the macromonomer have been determined. It has been established that, as the concentration of the methacrylic component is increased, the contribution of side reactions related to its anionic polymerization rises. It has been shown that macromonomers with caprolactone backbones and terminal methacrylic and hydroxyl groups may be obtained. A method has been proposed for the purification of polymerization products from low-molecular-mass impurities, such as dimethacrylates and diols.

Reactions of Functional End Group Redistribution over Macromolecules and their Characterization by Liquid Chromatography Under Critical Conditions

ABSTRACT Anionic polymerization of 2-hydroxyethylacrylate (HEA) and 2-hydroxyethylmethacrylate (HEMA) proceeding with formation of heterochain ether-ester oligomers was studied. Functionality type distribution of oligomers was characterized by liquid chromatography under conditions close to critical ones. Presence of macromolecules having different kinds of end groups (two acrylate, one acrylate and one hydroxyl, two hydroxyl groups on a molecule), as well presence of cyclic molecules was shown in oligomers. This fact indicates existence of intensive interchain exchange reactions in the course of polymerization. The possibility of carbon chain fragment formation was shown also. The mechanism of side reactions resulting in redistribution of functional end groups over macromolecules is revealed.

Regularities of the formation of silver nanoparticles with oligostyrylcarboxylate ligands

Regularities of the formation of silver nanoparticles with oligostyrylcarboxylate ligands during the one-step reduction of silver oligostyrylcarboxylates with triethylamine are studied via UV–Vis and IR spectroscopy. It is shown that the synthesis of silver nanoparticles occurs in a system with micellar organized molecules of the oligomeric precursor–ionomer. The formation of silver nanoparticles occurs through the successive formation of a diphilic silver oligostyrylcarboxylate/triethylamine complex, reduction of Ag+ in the cores of reverse micelles with the formation of (Ag0)n nuclei, and their subsequent growth through self-assembly.

Synthesis of water-soluble starlike poly(N-isopropylacrylamides) with fullerene C60 as a multifunctional core

New water-soluble starlike polymers with a fullerene core are synthesized via the radical polymerization of N-isopropylacrylamide in the presence of fullerene C60. The starlike structures of the polymers are studied by the methods of gel-permeation chromatography and scanning-electron microscopy.