Polymer Science, Series B最新文献

Size effects during chemical transformations in aerosols can lead to a shift in chemical equilibrium and a significant change in reaction rates. The most sensitive to them are polymerization processes, in which both the reaction rate and the degree of polymerization can depend on the number of monomers in a droplet. For the reversible polycondensation reaction, a kinetic equation is formulated based on the assumption that in a small volume, as conversion increases, the equilibrium molecular weight distribution (Flory distribution normalized to a finite number of monomers) is continuously reproduced. Kinetic curves were plotted to demonstrate the influence of droplet size on monomer conversion, degree of polymerization, and evolution of molecular weight distribution. The kinetics of polycondensation was modeled using the example of lactic acid polycondensation and compared with experimental patterns. The model demonstrates that a decrease in droplet size leads to a significant (power-law dependence on the radius) acceleration of the polymerization process and a decrease in the number-average mass of the polymer.

The intention of this research turned into to manufacture a new hybrid cloth referred to as poly(benzaldehyde-co-thiophene)/zinc oxide (PBT/ZnO) composites. The copolymer changed into synthesized the use of the chemical oxidative approach. Composites have been organized through stirring PBT and zinc oxide in dichloromethane at room temperature, with one-of-a-kind concentrations of zinc oxide (3, 7, and 10%). The researchers performed numerous analyses to study the structural and optical properties of the materials. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV/Visible spectroscopy had been employed for this reason. The optical gap energy values of the samples indicated their semiconductor behavior. Furthermore, the antimicrobial activity of PBT, PBT/ZnO 10% composite, and zinc oxide changed into evaluated in opposition to Escherichia coli, Staphylococcus aureus, and Candida albicans. The inhibition region diameter changed into measured as an indicator of antimicrobial efficacy. For Staphylococcus aureus, the inhibition region diameter of PBT/ZnO 10% composite turned into extra than that of PBT and the person zinc oxide. In the case of Candida albicans, the inhibition region diameter expanded with higher concentrations of zinc oxide. However, E. Coli showed mild sensitivity to the copolymer and become fairly resistant to each the composite and the zinc oxide. Overall, this research aimed to synthesize and analyze the properties of PBT/ZnO composites, inclusive of their structural, optical, and antimicrobial traits, highlighting their ability applications in diverse fields.

Two novel curing agents N-((4-(12-(4-(o-hydroxyphenylimino) methyl)phenoxy)dodecanyl-oxy)benzylidene)-2-hydroxybenzenamine) and N-((4-(12-(4-(p-hydroxyphenylimino)methyl)phenoxy)-dodecanyloxy) benzylidene)-4-hydroxybenzenamine) were synthesized and characterized by FTIR and NMR spectral analysis. A series of novel polymers were obtained via curing reaction of epoxy resin. The characterization of the thermosets was performed by FTIR spectral analysis. The photo-physical properties of the synthesized thermosets were evaluated by UV–Vis and photoluminescence spectral analyses. All the thermosets absorbed in the UV region (271–281 nm), which is attributed to the CH=N in conjugation with phenol moieties, incorporated into polymer network. Thermoset based on the synthesized curing agents emitted light in the blue region, which is attributed to the azomethine linkage in polymeric thermoset. Thermal stability and light emissive properties of the new polymer systems suggested their future use as a blue light emissive, thermally resistant adhesives.

Graft copolymers of chitosan with acrylic acid of three-dimensional structure have been synthesized. An increase in the concentration of the polysaccharide helps to accelerate the structure formation of copolymer macromolecules during the synthesis. It has been shown that one of the reasons for this effect is a local increase in the concentration of acrylic acid in the chain growth zone due to the formation of hydrogen bonds between the monomer and the polysaccharide. The graft copolymers have been characterized by IR and UV spectroscopy, AFM, and X-ray diffraction and can be used as highly swelling superabsorbents.

Monodisperse polymer particles of the core–shell type were produced using sequential emulsion and seed emulsion polymerization methods. The structure of the surface layer of the particles was studied using scanning electron microscopy. It has been established that sequential emulsion polymerization makes it possible to obtain particles with the lowest dispersity values of their diameter. The introduction of methyl methacrylate both at the stage of core synthesis and during the formation of the shell leads to the formation of spherical particles with a smooth surface layer. Based on such particles, films with pronounced properties of photonic crystals were obtained, and their Bragg reflection spectra in polarized light were studied.

A dietary supplement for the prevention of diabetes mellitus was obtained based on sericin separated from the cocoons of the silkworm Bombyx mori. By hydrolyzing Bombyx mori silkworm threads in an aqueous medium at a temperature of 110°C and a pressure of 0.143 MPa for 24 h, a sericin solution was separated. By evaporating the filtrate in a rotary evaporator, pure sericin powder with a molecular weight of 72 × 10³ and a yield of 29.8% was obtained. Subsequent repeated hydrolysis of pure sericin powder with the indicated molecular weight in an aqueous medium at a temperature of 130°C and a pressure of 2.8 MPa for 120 min resulted in the isolation of sericin powder with a molecular weight of (5‒6) × 10³, containing free amino acids, with a yield of 18.6%. The amino acid composition, molecular weight, and functional groups of sericin were determined using high-performance liquid chromatography, viscometry, and Fourier transform infrared spectroscopy. Sericin samples with different molecular weights were tested on rats with nutritional hyperglycemia. When sericin, containing free amino acids with a molecular weight of (5‒6) × 10³, was administered at a dose of 65 mg/kg twice a day, a decrease by 159.5% in blood sugar levels in the rats was registered after 30 days compared to the control group.

The polymerization of ethylene and propylene and the copolymerization of ethylene with 1-octene with novel type of post-metallocene catalysts containing ionic complexes [2L·M@dibenzo-18-crown-6]⁺ [TiCl₅·L]^– (L = CH₃CN, M = Li, K) are studied. The binary activator Al(C₂H₅)₂Cl/Mg(C₄H₉)₂ at [Al] : [Mg] ~ 3 is used as a cocatalyst. A linear crystalline polyethylene, an almost fully amorphous, atactic polypropylene, and statistical ethylene-1-octene copolymers containing from 2 to 9 mol % 1-octene are synthesized. The copolymers exhibit a broad molecular-weight distribution and a nonuniform composition distribution like copolymers synthesized over classical Ziegler–Natta catalysts and many post-metallocene systems.

An aliphatic dianhydride containing amide functionality (–NCOCH₃), ethylenediamine-N,N '-disuccinic acid anhydride (EDSA) was synthesized via base catalyzed N-alkylation of aspartic acid with 1,2‑dibromoethane followed by dehydration of the N-alkylated product with Ac₂O and pyridine. Four aliphatic polyimides (API) were prepared via two-step condensation polymerization of EDSA with four diamines (three straight chain aliphatic diamines and one alicyclic diamine). The polyimide film of EDSA with 4,4′-methylene bis(2-methyl cyclohexylamine) was almost colourless (cut of wavelength λ₀ = 312 nm and transmittance > 90% in the range of 450–800 nm). T₁₀ (temperature of 10% weight loss) of API were in the range of 417–457°C and T_g of 149–178°C. The API films exhibited low dielectric constants of 2.31–2.92 at 1 MHz.

Mixed hydroxy-aryloxy cyclotriphosphazenes have been synthesized via the interaction of hexachlorocyclotriphosphazene with a mixture of 4-allyl-2-methoxyphenol and diphenylolpropane (molar ratio 3.5 : 7.0). Their subsequent epoxidation with epichlorohydrin has afforded phosphazene-containing oligoepoxides with the phosphazene fraction of 50%. Optimal conditions for the synthesis of the composition-uniform phosphazene-containing oligoepoxides bearing one, two, and three epoxide groups in the phosphazene cycle have been elaborated. Such phosphazene-containing oligoepoxides can be cured with the curing agents common for the epoxy resins, to afford self-extinguishing compositions.

In this study, flower-shaped nano-silica was prepared through a calcination method, and then modified. Then using the method of free radical polymerization, and polysiloxane composite compounded with siloxane. The prepared composite microspheres combined the stability of polysiloxane with the unique surface morphology of flower-shaped nano-silica. The relative density of the composite material was controlled by the significant difference in density between siloxane microspheres and nano-silica. The structure and morphology of the composite microspheres were characterized and analyzed using FTIR, SEM, and other tests. The results showed successful compounding of siloxane and nano-silica, resulting in superhydrophobic polysiloxane/nano-SiO₂ composite microspheres with a water contact angle of 152°. The composite microspheres exhibited a nebula-like overall structure.