T. V. Volkova

Synthesis and characteristics of the composites based on poly(caproamide) and multiwalled carbon nanotubes

Polycaproamide composites are synthesized by the anionic activated bulk polymerization of ɛ-caprolactam in the presence of 0.1–5.0 wt % of multiwalled carbon nanotubes and using low-molecularmass monofunctional (N-acetyl-ɛ-caprolactam) and macromolecular polyfunctional (aromatic polyimides) activating agents. The effect of nanotubes on the polymerization of ɛ-caprolactam is studied, and this effect is shown to become more pronounced as the concentration of nanotubes is increased. The effect of nanotubes on the microstructure, phase composition, water sorption, thermophysical, mechanical, and friction characteristics of poly(caproamide) is analyzed.

Photopolymerization of (Meth)Acrylates in the Presence of Polyheteroarylenes

The free-radical photopolymerization of (meth)acrylates in the presence of a polyheteroarylene dissolved in a monomer has been studied. The kinetics of the radical polymerization of these monomers mediated by polyheteroarylene and the corresponding model compound has been investigated by differential scanning photocalorimetry and IR spectroscopy. Based on the experimental data, it is inferred that copolymers form due to chain transfer and/or chain termination to polyheteroarylene macromolecules. With the use of ESR spectroscopy, new radicals generated upon the addition of model polyheteroarylene compound to the initial solutions are discovered and characterized. The mechanism of the formation of copolymers is advanced.

Anionic polymerization of ε-caprolactam and its copolymerization with ω-dodecanelactam in the presence of aromatic polyimides

The anionic polymerization of e-caprolactam in the presence of aromatic polyimides as activators has been studied under adiabatic conditions. It has been shown that despite the crosslinked structure the produced graft copolymers of polycaproamide and polyimides contain the crystalline phase and are characterized by better water resistance and thermal stability, a higher content of the gel fraction, and improved mechanical properties as compared to copolymers prepared under the so-called isothermal conditions. It has been demonstrated that the catalytic system MgBr-e-caprolactam-aromatic polyimide may be used for the anionic copolymerization of e-caprolactam with ω-dodecanelactam, and experimental conditions providing a copolymer yield of 75% have been developed.

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.

Study of the physicochemical properties and film structure of ternary graft copolymers of aromatic polyimide, ɛ-caprolactam, and ω-dodecanelactam

The microstructure of films of ternary graft copolymers of aromatic polyimide, ɛ-caprolactam, and ω-dodecanelactam has been studied by atomic force microscopy. It is shown that an increase in the content of ω-dodecanelactam units in copolymers leads to an increase in the diameter of spherulites composed of fibrils. Simultaneously, water absorption decreases and the mechanical properties and crystallinity of copolymer films change.

Nanocomposites based on polymethylmethacrylate and silica

Nanocomposites based on polymethylmethacrylate and silica were synthesized by means of bulk polymerization. The morphology of the obtained polymer composites was studied by scanning electron microscopy. It was established that silica influences the mechanical and tribological properties of nanocomposites.

Role of nanofiller in friction of polymers based on polycaproamide: Indirect effect

The effect of nanofillers (multiwalled carbon nanotubes) on the tribological behavior of polycaproamide is studied when introduced into the polymer by polymerization filling. The introduction of insignificant quantities (∼0.1 wt %) of nanotubes provides their homogeneous distribution in the polymer and contributes to reducing the wear and friction coefficient. This is mainly due to the role of nanotubes as nucleators of the fine spherulitic polycaproamide structure. Such an indirect effect of the nanofiller on the polymer’s tribological behavior is seen when nanotubes are added to the melt in the course of granulation of polycaproamide compositions reinforced by carbon fibers, the effect of nanotubes being reduced with increasing amount of the reinforcing filler.

Formation of homopolymers, graft copolymers, and gel fraction during polymerization of monomer-polymer systems

The formation of homopolymers, graft copolymers, and the gel fraction in the course of polymerization of monomer-polymer systems has been studied. It has been demonstrated that the graft copolymers form at monomer conversions up to 30–40% and the intense accumulation of homopolymers corresponds to the degree of conversion at which autoacceleration begins. Structural features of the polymer composites have been revealed by electron microscopy measurements. The use of comonomers containing two double bonds has been shown to provide a way of controlling the properties of final polymeric materials.

Free-radical polymerization of monomer-polymer solutions initiated by a peroxide-tertiary aromatic amine system

The free-radical polymerization of styrene and methyl methacrylate initiated by the peroxide-tertiary aromatic amine system in the presence of dissolved aromatic polyethers and fluoroelastomer has been studied with the use of quantitative chemical, thermometric, and gravimetric analyses. It has been shown that the rate of polymerization of monomer-polymer solutions is higher than that of pure monomers. The influence of the content of dissolved polymers on the conversion of monomers corresponding to the onset of the gel effect has been estimated. In the presence of the polymer being added, this phenomenon manifests itself at a lower fractional conversion of the monomer. The greater the content of the polymer and the higher the viscosity of the reaction system, the sooner the rise in the rate of polymerization. The experimental evidence of this study makes it possible to control the synthesis of composite materials from monomer-polymer systems.

Polycaproamide films containing ionic liquids: Microstructure and properties

Films of polycaproamide and its composites containing ionic liquids (ILs) derived from 1-methyl-3-ethylimidazolium cation and N(CF3SO2)2 or N(CN)2 anions having crystalline structures were cast from solutions in formic acid. The structure and concentration of the ILs were shown to affect the conductivity (up to ∼10−4 S cm−1 25°C), microstructure (studied by X-ray diffraction, SEM, and AFM), and thermomechanical properties of the films.