Polymer Science, Series A最新文献

Herein, the SiO₂ nanoparticles were applied to decrease the thermal conductivity of cellulose acetate (CA) nanofibers via electrospinning and the oxygen-enriched method. Hence, solutions of CA and CA/SiO₂ were made by acetone/dimethylacetamide (2 : 1) with oxygen enriching and Helium gas. The nanofiber’s morphology and chemical structures were studied by SEM and FTIR, respectively. Finally, the media’s thermal conductivities were calculated using the two-plate Togmeter device test method based on BS 4745:2005, and the media’s tensile strength features were evaluated under the ASTM D638-10 standard. According to SEM images, SiO₂ nanoparticles incredibly covered the whole surfaces of CA nanofibers in the CA/SiO₂ medium in a cloud shape. FTIR vibration spectrums confirmed the siloxane bands vibrated at 475/75 cm^–1 in the CA/SiO₂ mat. Moreover, the thermal conductivity of the CA and CA/SiO₂ sheets were 0.1 W/(m K) with 0.225 ± 0.005 mm thickness and 0.044 W/(m K) with 0.461 ± 2.88 mm thickness, respectively. Additionally, the CA medium had 0.5 ± 0.28 MPa tensile stress at 2.57 ± 1.25% tensile strain and the CA/SiO₂ membrane had 0.561 ± 0.057 MPa at 1.81 ± 0.939%. Hence, the CA/SiO₂ nanocomposite medium has a super low thermal conductivity with good mechanical properties. Therefore, the characterization of the thermal conductivity of cellulose Acetate/nano-SiO₂ electrospun nanofiber composites for energy-saving, using an Oxygen-enriched method was completely successful.

For the first time using the density functional method in the 6-311++G(2df, 2p) basis set in the M06-2X hybrid functional approximation the nonplanar (dimensional) structure of sulfonyl chloride groups in chlorosulfonated polyethylene has been revealed. It has been shown that their structural features have a direct influence on the concerted mechanism of thermal degradation accompanied by the formation of a carbon-centered macroradical ({text{R}}_{n}^{ bullet }) and a chlorine atom Cl^•. The participation of these radicals in the processes of crosslinking macromolecules in the single-step production of thermoplastic vulcanizates has been experimentally verified.

RAFT polymerization was applied for the synthesis of hydrophilic poly(N,N-dimethylaminoethyl methacrylate) and random copolymers of N,N-dimethylaminoethyl methacrylate, containing 5 or 10 mol % of hydrophobic monomers methyl acrylate, methyl methacrylate, or butyl acrylate. The influence of chemical nature of hydrophobic comonomer and the copolymer composition on physico-chemical properties of polymers and their ability to strengthen friable (bulk) materials like quartz sand, clay, or limestone was systematically studied. It is shown that synthesized copolymers have relatively low glass transition temperatures, form aggregatively stable molecular solutions in water in a wide range of pH values, and have a pronounced surface activity, while their dried films demonstrate water-repellent properties. It is found that amphiphilic copolymers with a small content of hydrophobic comonomer units are much more effective as stabilizers of soils (bulk materials) in terms of mechanical strength and durability than the original hydrophilic homopolymer.

Using polarization and scanning electron microscopy and water vapor sorption the structure and properties of film composite nanomaterials based on hydroxyethyl cellulose and carbon nanotubes obtained in the magnetic field and outside the field have been studied. The films are anisotropic, which is associated with the formation of a liquid-crystalline phase during solvent evaporation from solution. Application of the magnetic field leads to the orientation of macromolecules and carbon nanotubess in the films, facilitating compaction of the structure of films and reduction in their ability to sorb water vapor. The Gibbs energies of the interaction of hydroxyethyl cellulose/carbon nanotube films obtained in the magnetic field and outside the field with water are calculated. For the films obtained in the magnetic field the negative values of the Gibbs energies decrease, indicating worsening of their interaction with water. With the introduction of carbon nanotubes into hydroxyethyl cellulose this effect becomes more pronounced.

Amorphous polyethylene terephthalate was oriented by rolling at room temperature on laboratory rollers. During rolling, a system of shear bands appeared, which was observed using crossed polarizers. The effect of rolling speed and degree on the shear band system was studied. At low rolling speeds (6.5 mm/min), plastic flow occurs through numerous fine shear bands. At higher speeds (above 1300 mm/min), a single serrated deformation zone is observed. This is explained by thermal softening of the polymer and a decrease in yield strength, which suppresses the formation of competing shear bands. At intermediate rolling speeds, two, three, four, or five serrated zones appear, spaced approximately equally. Increasing the degree of rolling leads to an increase in the number of serrated shear zones and homogenization of the flow process. The temperature in the shear bands was estimated, and it was shown that very slight heating of the bands is sufficient to prevent the formation of multiple fine shear bands. A significant difference was noted between the adiabatic deformation of the sample and the adiabatic shear bands.

The feasibility is considered of targeted production of interpolyelectrolyte complexes (IPECs) with an ordered supramolecular structure by polymerization in the composition of various polyelectrolyte–colloid complexes, direct mixing of polyelectrolytes in solution, and an interfacial reaction of polyelectrolytes. Using scanning electron microscopy and small-angle X-ray scattering, differences in the structure of interpolyelectrolyte complexes due to synthesis have been demonstrated. Methods for synthesizing IPEC dispersions with a controlled particle radius and the stability of such dispersions to dissociation into individual components are discussed, as well as some practical aspects of their use including laboratory testing of application potential.

The properties of nonionic and cationic molecular brushes, the copolymers of methoxy- or higher n-alkoxyoligo(ethylene glycol) methacrylates with dodecyl methacrylate and terpolymers additionally containing cationic units of N-methacryloylaminopropyl-N,N-dimethyl-N-propylammonium bromide, in water, organic solvents, and two-phase systems water–hydrocarbon and aqueous saline solution–hydrocarbon have been studied. Effect of the composition of molecular brushes, calculated values of their hydrophilic–hydrophobic balance, solvent polarity, and temperature on the solubility of the polymers, micellization (critical micelle concentration and sizes of macromolecular associates), phase transition conditions, and interfacial activity is estimated. A set of properties of the presented molecular brushes allows their inclusion in a number of potential polymeric micellar nanocontainers for controlled drug delivery into the body.

The drift of multiply protonated poly(ethylene oxide) chains in helium in electrostatic fields of various strengths is simulated using the molecular dynamics method. The simulation results are compared with the predictions of the kinetic theory of ion mobility, which relates the effect of increasing field strength to increasing ion temperature. As would be expected, the internal temperature of the ion T_ion increases with increasing random kinetic energy received by the ion from the field. However, it grows more slowly than expected in the two-temperature theory. Ion mobility is calculated as a function of the field strength E at constant gas temperature T (300 K) and as a function of T at low E. The results of these two series of calculations are compared at the same internal ion temperatures. The results coincide at T_ion close to T. At high ion temperatures, they diverge somewhat (by about 8% at T_ion = 600 K), which does not agree with the theory. Conformations and sizes of drifting ions, as well as their collision cross sections, calculated from the mobility, indicate that an increase in the number of attached protons leads to unfolding of the polymer chain. This effect is in satisfactory agreement with the Rayleigh criterion for the stability of a charged drop. An increase in field strength affects the collision cross section for several reasons. They include an increase in ion temperature leading to larger ion sizes, a decrease in the influence of long-range attractive interactions, and dipole alignment that is more pronounced with fewer protons attached.

In recent years, more and more researchers devote attention on the development and application ofbiodegradable, renewable, abundant, environmental-friendly and low-cost active packaging films, with appropriate antioxydante and antimicrobial properties. This paper focuses on developing composite poly (ε-caprolactone) (PCL) membranes reinforced with silver-zeolite nanoparticles (AgZ) prepared by solvent casting method. The resulting structural, thermal and surface properties of the nanocomposite materials were studied by using experimental characterization techniques such as Fourier-transform infrared (FTIR) analysis, UV-visible spectrophotometry, X-Ray diffraction (XRD), contact angle (CA), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The water vapor permeability (WVP) and the mechanical properties have been investigated. Experimental results showed that AgZ nanoparticles were well dispersed into PCL matrix leading to thermally stable nanocomposites with semi-crystalline structure and hydrophilic surfaces. More importantly, the nanocomposite films showed good antibacterial activity against Staphylococcus aureus and Salmonella enteric strains, demonstrating a potential application as an effective and safe packaging material to prolong the shelf life of food products.

Magnetorheological elastomers (MREs) are known to be smart composite materials able to storing and dissipating part of the energy when subjected to external excitation (magnetic field, temperature, frequency). In this paper, anisotropic magnetorheological elastomers containing 20, 30, and 40% of the micrometric iron particles MRE prepared. The magnetorheological characteristics such as, storage modulus, loss modulus and loss factor MRE measured by dynamic mechanical analysis (DMA) over a range of frequencies (0.01 to 100 Hz), strain amplitudes (0.01 to 20%) and temperatures (0 to 100°C). The magnetorheological elastomer during dynamic mechanical characterization is subjected to a constant magnetic field intensity value of 0.2 T. Increasing the excitation frequency also increases the magnetomechanical properties of the MRE. The temperature has a reversible effect with the frequency, we see that when we increase the temperature, the magnetomechanical properties of the MRE decrease. The experimental results precisely showed the variation of the dynamic moduli (storage modulus, loss modulus and shear loss factor) of the anisotropic MRE loaded with 20, 30, and 40% ferromagnetic particles as a function of the parameters of influence such as: frequency and temperature.