AbstractBionanocomposites are the gifts to present and future generations and can be utilized to tackle the issues of environment and sustainability. Bionanocomposites are basically hybrid materials, composed of natural polymers and some inorganic nanoparticle. In the present study, silver nanoparticle (AgNP) embedded gum acacia-tragacanth-cl-poly(acrylic acid) bionanocomposite has been synthesized, characterized and studied for dye adsorption. Three-dimensional cross-linked (AgNP) embedded gum acacia-tragacanth-cl-poly(acrylic acid) bionanocomposite structure has been confirmed with scanning electron micrography (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction investigations, and thermal degradation studies. Various factors such as time, nano-composite weight, dye concentration, and temperature were thoroughly investigated for efficient removal of textiles dyes like Crystal violet, Methylene blue, and Rhodamine-B. When compared to hydrogel, silver bionanocomposite demonstrated reduced swelling but a better dye adsorption capability (up to 94%). Furthermore, this bionanocomposite was tested for antimicrobial activity and it was found that GA-GT-cl-poly(AAc)/Ag bionanocomposite had far better antimicrobial activity in comparison to GA-GT-cl-poly(AAc) hydrogels. The excellent adsorption properties, along with natural antimicrobial activity make this bionanocomposite an efficient tool for the remediation of polluted water.

AbstractThe needs of the human communities to build low weight, high strength and durable structures have increased the demand for composite materials, including sandwich structures. In this case, sandwich panels are used in situations requiring high mechanical strength, low weight, sound insulation and thermal insulation properties. In this study, carbon nanotubes-reinforced composite honeycomb sandwich panels were constructed using silicone molding. To determine the role of carbon nanotubes on the compressive and bending behavior of sandwich panels, different amount of nanotubes was added to the epoxy resin. Also, different thicknesses were tested to determine the role of core wall thickness on the compressive and bending behavior of sandwich panels. The results showed that the compressive strength of honeycomb panels has a direct relation with the increase in the percentage of carbon nanotubes and the thickness of the wall. The compressive strength of sandwich panels increased from 42 up to 54 MPa with increasing carbon nanotubes from 0.025 up to 0.075 wt %. The compressive strength of sandwich panels with 5 mm honeycomb wall thickness and reinforced with 0.025, 0.05, and 0.075 wt % of carbon nanotubes compared to sandwich panels with 2.5 mm honeycomb wall thickness was respectively 2.4, 2.1, and 2.2 times. The flexural strength of 5-mm honeycomb wall thickness and reinforced with 0.025, 0.05, and 0.075 wt % of carbon nanotubes compared to sandwich panels with 2.5 mm honeycomb wall thickness, were respectively 3, 2.7, and 2.7 times.

AbstractA substrate is one critical factor for the wide application of flexible displays and electronic packaging materials in the future. Polyimides with high optical transparency, good thermal stability, dielectric properties, and nice mechanical properties are significant in substrates. A simple and feasible method to modify transparent polyimide films is to blend them with inorganic fillers. In this work, we successfully modified the transparent films by using phenyltriethoxysilane to synthesize trisilanol phenyl polyhedral silsesquioxane and adding it to the films. The introduction of trisilanol phenyl polyhedral silsesquioxane into the copolymer films resulted in the increase of high-temperature dimensional stability, optical performance, and mechanical properties of the films. The sample containing 5% of trisilanol phenyl polyhedral silsesquioxane exhibited a glass transition temperature of 322°C, coefficient of thermal expansion of 41.4 ppm/K, and tensile strength of 127 MPa, and the transmittance at 450 nm has reached 83.5%.

An Erratum to this paper has been published: http://doi.org/10.1134/S1560090422340012

Abstract—Effect of the structural mechanical modification via the crazing mechanism and composition of films based on HDPE nanocomposites and highly dispersed silica particles on the thermo-oxidative degradation and pyrolysis is studied. The incorporation of highly dispersed silica particles into the polymer matrix causes a reduction in the onset temperature of the intense weight loss of the composites by about 30°С and an increase in the temperature interval by 100°С under conditions of thermo-oxidative degradation. It is shown that in pyrolytic decomposition the HDPE‒SiO2 composite also starts to lose weight at lower temperatures (smaller by 50°С). Using various kinetic approaches to process the TGA curves the activation energy for each stage of thermal oxidation and pyrolysis is determined for structurally different HDPE-based samples. In the case of thermo-oxidative degradation, dependence of the activation energy on conversion is shown to be complex, thereby reflecting the multistage nature of the process. In pyrolysis, the activation energy is almost constant at all stages of the process. For various models of the processes, the activation energy is calculated by the Coats–Redfern method and the most probable mechanisms of thermal degradation and pyrolysis of the samples are proposed.

AbstractIn developing the concept of stimuli-responsive biodegradable hydrogels synthesis using dynamic covalent chemistry, gelation in a solution of low molecular weight N-(2-carboxyethyl)chitosan in the presence of vanillin is studied. It is shown that unlike chitosan its carboxyalkylated derivative can be used for the synthesis of hydrogels with good mechanical properties and low cytotoxicity. An analysis of the effect of vanillin : N-(2-carboxyethyl)chitosan molar ratio on the degree of functionalization of the polymer by a crosslinking agent and the rheological properties of the polymer in 3 М urea solution shows that, along with hydrophobic interactions, intermolecular hydrogen bonds play an important role in stabilizing the structure of the obtained hydrogels.

AbstractNovel rubber antioxidants, cysteine lanthanum and cysteine cerium, were applied in natural rubber composites. The anti-aging behavior of the composites with rare-earth complexes was systematically investigated via mechanical properties retention after aging, Fourier transform infrared spectroscopy-attenuated total reflection, thermo-oxidative stability and thermo-oxidative degradation kinetics. The results showed that rare-earth complexes could improve the mechanical properties of composites, decrease the formation of thermo-oxidative products and increase activation energy of the thermo-oxidative degradation. Compared with commercial antioxidant N-isopropyl-N '-phenyl-p-phenylenediamine, the vulcanizates with cysteine lanthanum performed better resistance to thermal oxidation aging. The outstanding anti-aging behavior of rare-earth complexes was attributed to not only the anti-oxidative effect between amino and sulfhydryl groups, but the trapping effect of rare-earth ions on free radicals.

AbstractPolyacrylate emulsions can be used as adhesives. However, low water resistance and insufficient adhesion have restricted their application. In this study, polyacrylate/silica composite adhesives were prepared by emulsifier-free polymerization. Fourier transform infrared spectroscopy results confirm that modified silica is successfully introduced into the emulsion. Thermogravimetry and differential scanning calorimeter indicate that with the increase of modified silica sol content, the thermal stability of the composite film is improved. When modified silica sol content increases from 0 to 8 wt %, the water contact angle increases from 74° to 98°, and the water sorption rate decreases from 16.5 to 7.8%. Moreover, with the addition of modified silica sol, the peel strength and tack of the modified latex changed slightly. Still, the shear strength on paper materials ranges from 148 min to over 1000 min when the content of modified silica sol reaches 8 wt %. The results show that adding modified silica sol can enhance the adsorption interaction between adhesive and paper material, effectively improving latex adhesive properties.

AbstractLiquid polycarbosilane substituted by allyl groups was prepared by the Grignard coupling reaction and reductive reaction synthesis with SiCl1.25(OCH3)1.75CH2Cl, Cl2CHSiMeCl2 and CH2=CHCH2Cl as the starting materials. The resultant polycarbosilanes were characterized by gel permeation chromatography, Fourier transform infrared and NMR spectroscopy. Moreover, the thermal properties and processing performance of polycarbosilanes were investigated. The ceramic yield of polycarbosilanes was about 77% at 1000°C, indicating that the polycarbosilanes have great potential to be promising precursors to SiC. With the increase of Cl2CHSiMeCl2 in the system, the viscosity of polycarbosilanes and C : Si ratio of ceramics increased, but the ceramic yield of polycarbosilanes decreased. Combining with its economical preparation, polycarbosilanes showed high potential as an economical SiC ceramic precursor for the fabrication of SiC matrix, coating and adhesives.

AbstractBranched polystyrenes are synthesized by the radical copolymerization of styrene and divinylbenzene with reversible inhibition (in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl) under deteriorating thermodynamic quality of the solvent. The resulting polymers are studied by size-exclusion chromatography combined with static light scattering, ozonolysis, NMR spectroscopy, and differential scanning calorimetry. The branched polymers synthesized by living radical polymerization are characterized by lower intrinsic viscosity values than their linear analogs. Kuhn–Mark–Houwink parameters for these polymers in a tetrahydrofuran solution (а = 0.29) confirm the nonlinear architecture of macromolecules and a high content of pendant double bonds comparable in the order of magnitude with their theoretical content in the absence of the cyclization reaction indicate their branched structure. The glass transition temperature of the branched polystyrenes is 20–35°С lower than the glass transition temperature of the linear polystyrene.

AbstractAligned carbon nanotubes (CNTs) were grown on silicon substrate coated with nickel film by chemical vapor deposition (CVD). Nickel film was pretreated to serve as catalyst for the growth of CNTs. The pretreatment process was investigated. The growth of CNTs followed the top growth mode. CNTs were functionalized to serve as initiators for the atom transfer radical polymerization (ATRP). Based on this, CNTs grafted with fluoropolymers were obtained. Then they were coated on paper. After drying, the surface was etched by steam and superhydrophobic surface was obtained. The water contact angle could reach 154.7°. The formation of superhydrophobic surface was due to the low surface energy and unique micro-nano composite structures of the membrane. The superhydrophobic surface exhibited excellent drag reduction performance. The high energy barrier prevented the transition from low energy state to metastable state. A stable Cassie state was maintained during fluid flow experiments.

Abstract—Polyampholyte–metal complexes based on polyacrylic acid; the aliphatic diamines ethylenediamine, 1,3-diaminopropane, and 1,4-diaminobutane; and Cu2+ was obtained by reacting aqueous solutions of polyampholytes and CuSO4. Using the method of simultaneous thermal analysis, it was found that the thermal degradation of the complexes occurs in three steps. The activation energy of thermal degradation of the polyampholyte–metal complexes is 22–99 kJ/mol. It was established by X-ray diffraction analysis that the products of thermal degradation of polyampholyte–metal complexes are heterogeneous systems composed of CuO and Cu2O phases, while catalysts based on them are heterogeneous systems consisting of Al2O3 and CuO phases. The size distribution of catalyst pores showed that the volume of pores with a diameter of less than 773 nm was 0.80–0.83 cm3/g, the specific surface area was 349–351 m2/g, and the predominant equivalent pore diameter was 6.2–6.3 nm. The mechanical crushing strength of catalyst pellets was found to be 7.1–7.3 MPa. In the process of CO oxidation to CO2, the catalyst began to exhibit its activity at 180–187°C; the complete conversion of CO in the oxidation reaction was achieved at 280–286°C. The performance of the obtained catalysts was 2.7–2.8 times higher than that of a reference sample.

AbstractTo prepare a uniformly network structured stimulus-responsive copolymer, organic polyethylene imine (PEI), polyethylene glycol glycidyl ether (PEGO) and inorganic calcium phosphate oligomers (CPO) as precursors, were used to prepare the PEI-PEGO-CPO hydrogels. The structure and properties of the products were characterized using infrared, 1H NMR and swelling behavior tests. The influence of CPO on temperature and pH sensitivity of the hydrogels was systematically investigated. The hydrogels were switched at temperatures between 20 and 60°C, pH values between 8 and 13. The results showed that the addition of CPO can effectively improve the temperature and pH responsive properties of the hydrogels. In addition, the hydrogels showed excellent reversibility for swelling–deswelling characteristics.

AbstractIn this study, ginger particles were incorporated in the sodium montmorillonite (Na+-MMT) structure and the effect of adding new nanoparticles (G-MMT) on the properties of polyurethane (PU) was investigated. The G-MMT was characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction analysis (XRD), and field emission scanning electron microscopy (FE-SEM). The nanocomposites and neat PU are characterized by FTIR, XRD, FE-SEM, electrochemical impedance spectroscopy (EIS), contact angle, and tensile tests. The EIS results showed that nanocomposite containing 3 wt % of G‑MMT show 2 × 1010 Ω cm2 resistance after 120 days of immersion in electrolyte solution. Due to the hydrophobic nature of G-MMT and its poor solubility in water, hydrophobic properties were observed in nanocomposites, which in the sample containing 3 wt % of G-MMT increased the contact angle to 72°. Also, the results of tensile test showed that by increasing the G-MMT content in the matrix, the mechanical properties are improved.

AbstractPolyethylene terephthalate is a linear thermoplastic polyester. Different grades of this polymer are used in various industries with a wide range of molecular weights and the manufacturing of beverage bottles. Due to its abundant waste products, it has become a problem for the environment. In this research, polyethylene terephthalate was reacted with ethylenediamine, butylenediamine, and hexamethylenediamine at a ratio of polymer 1 to 6 of each reactant. Polymer was then reacted with hydrazine hydrate in different molar ratios at various time intervals. The effect of catalyst concentration on the reaction yields was studied. It was observed, that with the increase of aliphatic groups in the structure of the final product its melting point was lower which might have been due to the presence of more flexible methylene groups in the final structure.

AbstractThe catalytic activity of seven titanium complexes with a [OSNO]-type bis(phenolate) ligand in ethylene polymerization has been studied at mild conditions of ethylene pressure (1.2 atm) and room temperature. It has been shown that in the presence of methylaluminoxane or triisobutyl aluminum modified methylaluminoxane cocatalyst, the activities of the titanium catalytic systems reach 86 kg PE/((mol catalyst) h) and lead to the preparation of ultrahigh-molecular-weight polyethylene. [OSNO]-type bis(phenolate) ligand structures have a great influence on the structure and molecular weight of polyethylene. The resulted polyethylenes are low long-chain branched polyethylene (n ≥ 6) or linear polyethylene and the melting temperatures of these polyethylenes are about 128–133°C.

AbstractOligomeric aryloxycyclotriphosphazenes with mixed functional groups are synthesized by the interaction of hexachlorocyclotriphosphazene and two phenols, methyl-4-hydroxybenzoate (paraben) and 4‑allyl-2-methoxyphenol (eugenol), at different order of their introduction into the reaction mixture. The hydrolysis of ester groups of aryloxycyclotriphosphazenes yields corresponding carboxyphenoxycyclophosphazenes, and the oxidation of their allyl groups by m-chloroperbenzoic acid affords epoxy derivatives. Optimal conditions for the indicated transformations are determined, and structure of the resulting oligomers is studied by 1Н and 31Р NMR spectroscopy and MALDI-TOF mass spectrometry.

AbstractRadical polymerization of acrylonitrile in the presence of N-methylmorpholine N-oxide has been performed for the first time. It has been shown that the presence of N-methylmorpholine N-oxide leads to the decrease in the molecular mass of the polymer and induces its partial cyclization. These features have been preserved when N-methylmorpholine N-oxide has been introduced in the polymerization simultaneously with the monomer and the initiator as well as when it has been added at high conversion of the monomer. The introduction of N-methylmorpholine N-oxide into polyacrylonitrile has led to the cyclization of the nitrile units in two stages, the low-temperature one being initiated by N-methylmorpholine N-oxide and the high-temperature one, typical of pure polyacrylonitrile. The ratio between the intensity of these processes has been governed by the content of N-methylmorpholine N-oxide.

AbstractThe magnesium oxide whisker was commonly used as reinforcement for polymer. In this study, magnesium oxide whisker was firstly modified by γ-aminopropyl triethoxysilane and n-octadecylamine activated by N,N'-carbonyldiimidazole. Then the modified magnesium oxide whisker was introduced into oil-impregnated monomer casting nylon. The final composite was obtained by in situ polymerization. The mechanical and tribological properties of composite with different contents of modified magnesium oxide whisker were investigated. The results showed that the mechanical and tribological performances of the composites were observably improved by growth of tensile strength, flexural strength, elongation at break, and impact strength. The tribological test results indicated that reduction in the frictional coefficient and the abrasion loss was achieved. The surface lipophilicity of composites obviously increased also. This work provided a simple method for designing composites with excellent mechanical and frictional properties which may greatly broaden the application potential of composites.

AbstractIn this study, the macroinitiator poly(hexafluorobutyl methacrylate) (PHFBMA) was first prepared by atom transfer radical polymerization (ATRP) method, and then PHFBMA-b-PHEMA block copolymer was prepared by ATRP method using hydroxyethyl methacrylate (HEMA) as the monomer. After that, the amphiphilic diblock copolymer was used to construct a porous membrane using breath figures. Surface hydrophobicity is one of the important properties of materials. It is inspired by the principle of nepenthes predation, that the slippery liquid-infused porous surface (SLIPS) mimics the inner wall structure of the pitcher plant. In order to enhance the surface hydrophobicity of the fluoropolymer coating, the silicone oil infused on the ultra-slip surface is innovatively modified by nano-SiO2 filling. When the content of polysiloxane is unchanged (10 mL for silicone oil and 0.5 g for polysiloxane), the modified silicone oil filled with 1.5 g of nano-SiO2 owns the best modification effect at the film concentration of 37.5 mg/mL. The results show that the hydrophobic properties of the SLIPS are greatly improved compared with the porous film. The water contact angle of SLIPS is 160o, the sliding angle of SLIPS is 7°. In addition, due to the presence of surface silicone oil, the SLIPS has good resistance to bacterial adhesion.