E. O. Perepelitsina

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.

Synthesis of new branched urethane-triazole polymers

An AB2 monomer obtained via the reaction of hexamethylene diisocyanate with 1,3-diazidopropan-2-ol and 2-propyn-1-ol contains one triple bond (A) and two azide groups (B2). Open image in new window Hyperbranched urethane-triazole polymers were synthesized through stepwise polymerization of this monomer via 1,3-dipolar cycloaddition. Owing to the presence of impurities of compounds with four azide groups (the products of the reaction of hexamethylene diisocyanate with two molecules of diazidopropanol) and two propyne groups (the product of the reaction of hexamethylene diisocyanate with two molecules of 2-propyne-1-ol) in the aforementioned monomer, uretane-triazole “polymers” are not classical huperbranched polymers, they are highly branched polymers that are soluble in aprotic polar solvents and have weight-average molecular masses of 5–260 and values of the exponent in the Kuhn-Mark-Houwink equation of 0.23–0.36.

Effect of branched copolymers on the kinetics of polymerization of MMA and the structure and properties of the resulting polymers

It has been shown that the free-radical polymerization of MMA carried out in the presence of branched PMMAs of various compositions and structures proceeds as a crosslinking process. Branched PMMAs containing reactive C=C bonds serve as weak crosslinking agents; polymers formed in their presence are rarely crosslinked macromolecular structures. The kinetic features of the polymerization of MMA performed in the presence of branched PMMAs and the structure and properties of the polymers are determined by the content of branched PMMAs in the starting monomer-polymer mixture and their structure and physicochemical characteristics.

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.

The influence of reagent concentration on the kinetics of carbon dioxide-propylene oxide copolymerization in the presence of a cobalt complex

The effect of the concentrations of propylene oxide and the catalyst (salen)CoDNP/[PPN]Cl ((salen)CoDNP: [PPN]Cl = 1: 1, mol/mol) on the kinetics of the copolymerization of CO2 and propylene oxide at 0.5 MPa and 20°C has been studied. The reaction proceeds at a constant rate after an induction period, and the value of this period varies with the reagent concentrations. The steady-state reaction rate increases linearly with the propylene oxide concentration in the range 5.0–14.3 mol/L. At high catalyst concentrations, such as (5.2–7.3) × 10−3 mol/L, the reaction rate is first order in the catalyst; at concentrations below 5 × 10−3 mol/L, the reaction rate is second order in the catalyst. Molecular mass increases in proportion to the propylene oxide conversion, that is consistent with a living polymerization process. A regioregular copolymer with 96% head-to-tail (HT) connectivity of propylene oxide has been obtained.

Mechanical and thermal properties of ternary alternating copolymers of carbon monoxide with olefins

Thermal properties and the deformational behavior of ternary alternating copolymers of carbon monoxide with ethylene and other olefins (propylene, 1-butene, styrene) with molecular masses of Mn = 1000–35000 and molar fraction of the third comonomer in the polymer chain from 0.02 to 0.70 were investigated. Temperatures of melting and glass transition are significantly affected by the composition of the products. Varying the nature of the third comonomer or the content of its units in the polymer chain and the molecular masses of terpolymers makes it possible to obtain materials with Young’s moduli of 0.003–3.090 GPa and elongations at break of 5–2000%.

Problems in the size exclusion chromatography of poly(N-isopropylacrylamide) on styragel columns

The molecular weights of poly(N-isopropylacrylamide) (PNIPA), calculated according to polystyrene calibration standards upon the elution of THF on styragel columns, appear to be much lower than their actual values determined using independent approaches. This is likely due to interactions between the nitrogen-containing units of PNIPA polymer chains and the sorbent, so the polymer is eluted in the mode intermediate between exclusion and critical. An effective exclusion mode during the elution of PNIPA on a styragel column can be achieved by using an eluent more polar than tetrahydrofuran (particularly, 1-methylpyrrolidone).

Anionic polymerization and copolymerization of acrylonitrile initiated by systems based on bicyclic tertiary amines and ethylene oxide

It is shown that the products of interaction of ethylene oxide and bicyclic amines containing tertiary nitrogen atoms at the tops of bicyclic structures efficiently initiate the anionic polymerization of acrylonitrile. As opposed to all known initiators of this process, the mentioned initiating systems contain no metal atoms or atoms of elements heavier than oxygen. The polymerization of acrylonitrile under the action of the ethylene oxide–bicyclic amine system in a polar medium (dimethyl sulfoxide) at room temperature occurs in the homogeneous regime over several minutes, while, in a weakly polar solvent (tetrahydrofuran), polymerization occurs in the heterogeneous regime over several hours. The reaction may become homogeneous in a mixture of these solvents at both room temperature and a lower temperature. The number-average molecular masses of the polymers, depending on polymerization conditions, are in the range from 25 × 103 to 480 × 103 and their polydispersity indexes are from 1.55 to ~3.40. It is found that the copolymers of acrylonitrile with oxygen-containing acrylic monomers, as well as with ethylene oxide, can be prepared.

The kinetics of carbon dioxide and propylene oxide copolymerization catalyzed by binary catalyst system

The kinetics of carbon dioxide and propylene oxide copolymerization was investigated in order to obtain Arrhenius parameters for the reaction in the presence of the efficient binary catalytic system (salen)Co(DNP)/[PPN]Cl. The reaction rate was followed by measuring the uptake of carbon dioxide during copolymerization. The steady-state rate of the reaction reaches a maximum value at carbon dioxide pressure of 0.6–0.7 MPa. At the reaction conditions, the dependences of the reaction rate on the concentrations of reagents follow the first-order kinetic low. The value of effective activation energy is equal to 45.7 ± 2.0 kJ/mol, and pre-exponential factor in the Arrhenius equation is equal to (5.1 ± 0.1) × 105 L2/(mol2 s). The poly(propylene carbonate) produced was shown to be a regio-regular copolymer with a bimodal molecular weight distribution.

Ethyl acrylate copolymers as promising porogens for the synthesis of polydimethacrylates with controlled porous structures

The crosslinking radical polymerization of triethylene glycol dimethacrylate in bulk in the presence of 0–40 wt % ethyl acrylate-based copolymers of various compositions is studied, and some structuralphysical properties of the crosslinked polymers are investigated. The quantitative characteristics of their porous structures, such as the specific surface areas and the total pore volumes, are measured via the low-temperature adsorption of nitrogen. During sol-gel analysis, polymer additives are removed from network polymers with the use of benzene and pores with sizes from 4 to 500 nm occupy their places. The maximum specific surface area is approximately 17 m2/g. It is found that the specific surface area and total pore volume depend on the content of the polymer additive in the initial composition.