G. G. Nikiforova

Synthesis and properties of siloxane(ethylene oxide)urethane block copolymers

A new approach to the synthesis of hydrolytically stable dimethylsiloxane-ethylene oxide polyblock copolymers is described, in which ethylene oxide and siloxane blocks are linked by urethane groups. The molecular-mass parameters of block copolymers of different compositions are determined by capillary viscometry, light scattering, and gel-permeation chromatography. The temperature transitions in copolymers are characterized by differential scanning calorimetry.

Ionomers of a new type based on sulfonated polyphenylquinoxalines

This communication is devoted to new type iono mers belonging to the class of aromatic ionogenic polymers—sulfonated polyphenylquinoxalines (SPPQ). The interest in SPPQ is due to the fact that the parent polyphenylquinoxalines (PPQ) are promising poly heteroarylenes combining high thermal characteristics and chemical stability with excellent solubility in organic solvents and good film forming properties [7]. Therefore, SPPQ formed upon polymer analogous transformation of PPQ upon sulfonation with a mix ture of sulfuric acid and oleum [8] can be considered as potential effective thermally stable polymeric elec trolytes and as the basis for the production of promis ing thermally stable aromatic ionomers for various applications.

Three-Dimensional Free-Radical Copolymerization of Methyl Methacrylate with Diunsaturated Monomers in the Presence of an Aromatic Polyimide

The three-dimensional free-radical copolymerization of MMA with diunsaturated comonomers of various natures in the absence and in the presence of 4 wt % aromatic polyimide (ηinh = 0.38−1.02 dl/g) has been studied by isothermal calorimetry. It has been shown that, depending on the chemical nature of spacers separating double bonds of the comonomers, the kinetic curves of copolymerization may be divided into two groups, one of which is characterized by an almost complete absence of stationary portions. It has been demonstrated that the effects of the polyimide on the initial rate of copolymerization and on the parameters of the gel effect depend on the nature of diunsaturated comonomers and the molecular mass of the aromatic polyimide. The swelling of the polymer systems under study in toluene has been investigated, and the parameters of their network structure have been estimated. The irreversible flow deformation of the MMA copolymers with diunsaturated comonomers does not manifest itself up to a temperature corresponding to the onset of degradation of the copolymers. The incorporation of polyimide units improves the thermal stability of the copolymers.

Sulfonated poly(naphthoylenebenzimidazole) and its modification with an alkali metal cation

A method for sulfonation of poly(naphthoylenebenzimidazole) with oleum–sulfuric acid mixture to produce sulfonated poly(naphthoylenebenzimidazole)s (SPNBIs) with different content of–SO3H groups has been developed. SPNBIs containing ≥5% sulfur are soluble in NMP and form stable solutions. It has been revealed that viscosity of SPNBI solutions in NMP increases on decreasing concentration when the content of polar sulfonic groups enhances with sulfonation degree of the initial polymer. Thus, SPNBI shows the polyelectrolyte effect. The substitution of hydrogen atoms in sulfonic groups by an alkali metal ion, potassium, has been conducted by the treatment of SPNBI powders with 5 M KOH aqueous solution under heterogeneous conditions. Potassium salts of SPNBI are insoluble in NMP. The introduction of potassium ions into SPNBI leads to the preparation of ionomers with a thermal stability higher than that of the initial PNBI.

Phase Structure and Properties of Blends Based on Polystyrene and Carbosilane Dendrimers

Blends based on polystyrene and first- and third-generation carbosilane dendrimers with dimethyl(2-phenylethyl)silyl)propyl terminal groups are studied. For the same chemical structure of the outer layer, a change in the radii of nanoparticles from 0.9 to 2.0 nm entails a sharp decline in the rate of their mass transfer to the polymer bulk. Dendrimers of the first and third generations are characterized by substantially different compatibilities with polystyrene. It is assumed that this effect is associated with an increase in the energy of interaction between dendrimers. When dendrimers of the first generation are introduced into polystyrene, the viscosity, glass-transition temperature, and storage modulus decrease, while the filling of polystyrene with dendrimers of the third generation insignificantly affects these characteristics of the polymer.

Relaxation properties of gradient polymer materials based on network poly(urethane-isocyanurates) produced via a modified method

The relaxation properties of gradient polymer materials produced via a modified method are studied through dynamic mechanical analysis and through measurement and approximation of stress-relaxation curves in a wide temperature range under static conditions. The physicomechanical properties of polymer materials produced via the new method are substantially improved, and the range of properties is markedly widened. The investigated materials can possess any values of the elastic modulus, including those inherent in the region of transition from the glassy state to the rubbery state; moreover, they demonstrate a quasi-elastic behavior characteristic of glasses and rubbers.

Synthesis of amorphous block copoly(arylene ether ketones) and their characterization

Exchange reactions that may proceed in the course of polycondensation during formation of a polymer from 4,4′-difluorobenzophenone and 4,4′-(isopropylidene)diphenol have been studied. It has been shown that the molecular mass of the polymer decreases under the action of 4,4′-(isopropylidene)diphenol diphenolate. The nucleophilic substitution of the activated aryl halide in DMAA in the presence of potassium carbonate yields high-molecular-mass block copoly(arylene ether ketones) based on 4,4′-difluorobenzophenone and a number of bisphenols. It was demonstrated the synthetic procedure and the chemical structure of block copoly(arylene ether ketones) strongly affect the onset temperature of softening and the mechanical characteristics of the films based on these polymers.

Dynamic mechanical and thermal characteristics of homopolymers and copolymers containing arylene ether ketone units with carboxylic side groups and their salts

Properties of a poly(arylene ether ketone) with carboxyl side groups, copolymers containing units of this homopolymer, and their salts with different degrees of neutralization by alkali metals were studied by the methods of dynamic mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry. By varying the nature of a metal atom and the degree of neutralization of carboxylic groups of a homopolymer and their content in copolymers, one may change the properties of polymers, including their ability to form ion pairs and, hence, their glass transition temperatures. For polymer salts at the 100% neutralization of carboxylic groups, the storage modulus and the glass transition temperature are shown to increase with decreasing the radius of the metal ion. The thermal stability of poly(arylene ether ketone) with carboxylic side groups and copolymers with different contents of such groups may be controlled by varying the nature and content of the introduced metal.

Modification of sulfonated polyphenylquinoxaline by alkali and alkaline earth metal cations

Salts of sulfonated polyphenylquinoxaline (SPPQ) containing alkaline earth metal ions—Mg2+, Ca2+, and Ba2+—were synthesized. The paper considers their solubilities, the properties of solutions, and thermal stability in comparison with analogous characteristics of SPPQ salts with alkali metals. The introduction of alkaline earth metal cations into SPPQ affords soluble polymeric salts having high thermal stability. Solutions of SPPQ salts in N-methylpyrrolidone (N-MP) containing Mg2+, Ca2+, and Ba2+ ions do not exhibit polyelectrolyte properties, unlike solutions of SPPQ salts in which the counterions are Li+, Na+, and K+. Solutions of SPPQ and its salts in N-MP can be converted to water-soluble form by dialysis. This opens up new prospects for using the polymeric salts.

Structuring in solutions of polydiphenylenesulfophthalide salts and their combined systems with a cationic surfactant

New derivatives of polydiphenylenesulfophthalide, namely its alkali-metal salts and interpolymer complexes with a cationic surfactant, are prepared via polymer-analogous transformations. It is shown that, depending on the type of solvent, solutions of polydiphenylenesulfophthalide salts may feature the properties of polyelectrolytes or ionomers. On the basis of dynamic laser light scattering data, the sizes of associates formed in solutions of salts of polydiphenylenesulfophthalide and its complexes with cetyl pyridinium chloride are determined. With the use of dynamic drop tensiometry, the values of surface tension of the aqueous solutions of lithium polydiphenylenesulfophthalide and its complexes with cetyl pyridinium chloride, as well as viscoelastic characteristics of adsorption layers formed at the solution/air interface, are measured.