V. S. Papkov

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.

Heterophase Polymerization of Styrene in the Presence of Organosilicon Compounds of Various Natures

The heterophase polymerization of styrene has been carried out in the presence of surfactants—organosilicon compounds with different solubilities in aqueous and styrene phases and surface activities at the interface. It has been demonstrated that the stability of polymer suspensions prepared with water-insoluble organosilicon compounds is much higher than that in the presence of organosilicon surfactants soluble in organic and aqueous phases. In the former case, suspensions with narrower particle-size distributions are produced. The stability of polymer microspheres prepared at various monomer-to-water volume ratios has been tested. An increase in the monomer concentration above 25 vol % leads to the loss of system stability.

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.

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 separation in aqueous solutions of polyethylaminophosphazene hydrochloride during heating

It is shown that aqueous solutions of polyethylaminophosphazene hydrochloride undergo phase separation during heating. This phenomenon is studied in detail at pH 3.5 (0.1 M citrate buffer) in relation to the composition of the system with the use of nephelometry and high-sensitivity DSC. The cloud points and the enthalpy of phase separation of the system are determined, and its phase diagram is constructed. The system features a lower critical solution temperature: w 2,cr = 7.3 × 10−4 and T cr = 34.3°C. The enthalpy of phase separation is 12.8 ± 0.6 J/g of the polymer, regardless of the system composition. A new approach to the analysis of DSC data on the phase separation of aqueous solutions of polymers during heating is advanced on the basis of calorimetric parameters coupled with the data on the composition of coexisting phases. Through this approach, the main contribution to the heat effect of phase separation of the system under study is related to a change in the energy state of a polyethylaminophosphazene hydrochloride molecule as a result of its dehydration.

Synthesis and thermal and rheological properties of carboxyl-containing polydimethylsiloxanes

A number of polydimethylsiloxanes modified with fragments of undecenoic acid and its esters were synthesized. The structures of polymers were confirmed by 1H and 29Si NMR spectroscopy. The rheological properties of obtained polymers were studied, as well as their thermal properties were studied by DSC.

Rheological properties of nonfunctional derivatives of hyperbranched polycarbosilanes

The rheological properties of melts of nonfunctional hyperbranched polycarbosilane polymers differed in regularity of the structure and chain length between the branch points were studied for the first time. Unlike melts of linear polymers, the studied hyperbranched systems are Newtonian fluids, and the viscosity and activation energy of their viscous flow depend substantially on the molecular parameters and regularity of the molecular structure.

Synthesis, rheological, and thermal properties of polydimethylsiloxanes modified with long-chain hydrocarbon substituents with polar fragments

A number of polydimethylsiloxanes modified with long-chain hydrocarbon substituents with ester or benzylamide terminal groups was synthesized by hydrosilylation and polymeranalogous reactions. The copolymers were characterized by 1H NMR spectroscopy, gel permeation chromatography, and differential scanning calorimetry. The influence of the type and content of modifying substituents on the low-temperature and rheological properties of the copolymers was established and indicates an increased level of intermolecular interactions in the synthesized copolymers compared to PDMS.

Structuring in aqueous solutions of polydiphenylenesulfophthalide: dimensions of associates and their local mobility

The dimensions of associates formed in aqueous solutions of polydiphenylenesulfophthalide (PDPSP) and products of its treatment with alkali-metal hydroxides are measured by light scattering. As shown by EPR spin-probe spectroscopy, the associates are hydrophobic structures. The local mobility of polydiphenylenesulfophthalide associates is lower than that of associates of the polymer treated with alkalimetal hydroxides, but, in all cases, this value is commensurable with the local mobility of solid polystyrene.

Unwinding of ι-carrageenan double helix upon complex formation with polyethylaminophosphazene hydrochloride

The interaction of poly(ethylaminophosphazene) hydrochloride (MSD = 3.2 × 105) with potassium ι-carrageenan (Mw = 2.2 × 105), which is a linear regular anionic polysaccharide, has been studied by high-sensitivity DSC at pH 3.8 in a 0.15 mol/l solution of KCl. The dependences of temperature, enthalpy, and the cooperativity parameter of the double helix-coil transition of polysaccharide on the concentration ratio of polyphosphazene and polysaccharide have been obtained. The presence of polyphosphazene has no effect on the temperature and cooperativity of transition, whereas the enthalpy of the transition decreases linearly with the content of polyphosphazene and turns to zero at a mass polymer-to-polysaccharide ratio of approximately 1: 1, which corresponds to the equivalent concentrations of polyphosphazene and polysaccharide with respect to charges. Our data indicate that the mixing of poly(ethylaminophosphazene) hydrochloride and potassium ι-carrageenan solutions gives rise to formation of the stoichiometric interpolyelectrolyte complex, in which the polysaccharide loses its ability to form double helix typical of ι-carrageenan in saline solution (0.15 M KCl).