Polymer Science, Series A最新文献

Cellulose nanocrystals were extracted by the method of acid hydrolysis of microcrystalline cellulose, and a simple one-pot method of dissolving polyvinyl alcohol and cellulose nanocrystals in dimethyl sulfoxide/water is proposed to prepare ionic conductive organohydrogels. Transmission electron microscope, ultraviolet-visible spectrophotometer, X-ray diffraction, Fourier transform infrared spectroscopy, universal material testing machine, electrochemical workstation, and the LCR digital bridge tester were used to study the microscopic morphology, light trans-mission properties, mechanical performance, electrical properties and sensing properties of the organohydrogel. The results show that the ionic conductive organohydrogels exhibit high stretchability (377% strain), firmness (strain at break to 345.51 kPa), good transparency and high gauge factor 4.63 (0–400% strain). The tensile fracture test shows that the organohydrogel has good toughness and elasticity in terms of tensile strength and toughness. Moreover, the PVA/CNC organohydrogels were used as the conductive medium to form a self-powered strain sensor and wearable strain sensor, and the open-circuit voltage of the self-powered system could reach 0.859 V, indicating that the organohydrogel has good electrical conductivity and sensor’s stability.

Collecting water from the air could alleviate freshwater shortages in arid regions such as remote and inland areas. However, it is challenging to prepare adsorption materials that have high adsorption and desorption performance using straightforward synthesis routes for water harvesting applications. In this paper, a polydopamine (PDA)@Sodium polyacrylamide carboxymethyl cellulose (PAM-CMCNa)-calcium chloride (CaCl₂) composite aerogel (PDCA) with a vertical channel was prepared by salt template method and photopolymerization for atmospheric water collection (AWH). The designed vertical channel promotes the rapid transport of water molecules from the atmosphere to the interior of the hydrogel through capillary action. During this process, the hydrogel further expands to prevent the leakage of the internal salt solution, which effectively improves the water vapor adsorption and desorption by hydrogel. Experimental results showed that the hydrogel can absorb 2.78 g/g of water at 90% relative humidity (RH), where 56.3% of the captured water can be desorbed within 60 min of exposure under 1.0 sun light intensity. After 10 adsorption-desorption cycles, the PDCA still possesses excellent water sorption performance. The indoor water collection test showed that the water collection performance reached 2.143 kg/kg day at 90% RH and 25°C adsorption for 12 h and desorption for 6 h. The proposed method for the preparation of PDCA composites can achieve high water harvesting performance over a wide humidity range to enable solar-driven clean water production in remote areas.

A series of blend membranes based on sulfonated poly(arylene ether phosphine oxide) (sPEPOF) and trisulfonated poly(phthalazinone ether phosphine oxide) (tsPPEPO) were prepared and studied. These blend membranes showed good compatibility, which might be ascribed to the excellent adhesive ability of the phosphine oxide groups and the strong intermolecular interaction. The properties of the blend membranes such as water uptake, swelling, proton conductivity, oxidative stability and methanol permeability were characterized in detail. The results showed that 7.5% weight content of blending tsPPEPO was beneficial to improve the blend membrane’s dimensional stability, oxidative stability, methanol resistance, and simultaneously keep considerable proton conductivity. For example, the blend membrane tsPPEPO-7.5 has an in-plane swelling of 8.2% and a through-plane swelling of 4.9% at 80°C, which are lower than those (14.1 and 13.0%, respectively) of the original sPEPOF membrane. At the same time, it has a conductivity of 0.080 S/cm, and its methanol permeability is about one-thirtieth of that of Nafion 117. Furthermore, the oxidative stability is also remarkably improved compared with that of the original sPEPOF membrane. Therefore, tsPPEPO is an ideal blend component for the achieved blend membranes, which exhibited excellent overall properties and application prospect.

A theoretical model describing the self-assembly in dilute solutions of amphiphilic macromolecules containing the backbone built of the solvophilic units (the P groups) and the solvophobic side chains (the H groups) possessing orientational mobility relative to the backbone units has been elaborated. In the framework of strong segregation limit (The size of the insoluble regions of the formed micelles is on the order of the hydrophobic side chains), state diagrams of the solution have been calculated with and without accounting for the orientational entropy contribution of the side groups to the total free energy of the solution at different thermodynamic qualities of solvent for the macromolecules and the grafting density of the H groups; the regions of stability of spherical and cylindrical micelles as well as planar bilayers (vesicles) have been revealed. It has been found that the contribution of the orientational entropy significantly affects the view of the state diagrams. In the case of considering the orientational mobility, the conditions of the cylindrical micelle stability are very sensitive to the change in the grafting density of the side groups. This sensitivity can be the reason why the formation of long cylindrical (wormlike) micelles is not observed in experiments and computer simulations. As earlier demonstrated at a qualitative level, the orientational mobility of the side groups can lead to the emergence of the orientation-induced attraction between the polymer micelles (A. I. Buglakov, D. E. Larin, and V. V. Vasilevskaya, Polymer 232, 124160 (2021)). In this study, exact analytical calculations of the energy of orientation-induced attraction for the case of the interaction between two planar bilayer micelles has been performed. At distances being of the order of the size of the side H group, the orientation-induced attraction forces are much stronger than the van der Waals forces and, hence, the orientation-induced attraction can be decisive in the formation of large aggregates observed in experiments.

Protonated diallylammonium polymers are special among cationic polyelectrolytes, due to a series of properties including high antimicrobial activity, for example, towards Mycobacterium tuberculosis. The polymers samples should be characterized properly for their practical application. In this study, protonated secondary polydiallylamines based on diallylammonium trifluoroacetate have been synthesized via radical reversible addition−fragmentation chain-transfer polymerization in the presence of 2-[(ethoxycarbonothioyl)sulfanyl]acetic acid. The NMR spectroscopy data have shown that the macromolecules contain the dithiocarbonyl terminal groups enhancing the polymer solubility in nonaqueous media, for instance, in methanol. The obtained polymers have been investigated by means of hydrodynamics and dynamic light scattering methods; molecular mass and hydrodynamic parameters of the macromolecules have been determined. Comparison of the polymers with similar ones synthesized via conventional radical polymerization and bearing terminal vinyl groups has revealed the independence of their hydrodynamic properties in 1.0 mol/L NaCl on the synthesis method and the terminal groups structure at М > 8 × 10³, thus allowing the application of the scaling relationships for the diallylammonium polymers to determine the molecular mass, irrespectively on the preparation methods.

Poly(butylene terephthalate) is a rigid polymer with poor elasticity and impact resistance. In this research, thermoplastic polyurethane is mixed with poly(butylene terephthalate) through injection molding to improve the impact strength and elasticity of the blend. The findings revealed that the blend had higher impact toughness but lower tensile and flexural strengths when compared to neat poly(butylene terephthalate).

Reactor polymer compositions (RPCs) based on UHMWPE with M_w = 1000 kg mol^–1 and low molecular weight HDPE (LMWPE) were studied. Two series of UHMWPE compositions were used to determine the influence of the molecular weight and properties of the LMWPE fraction on the morpho-logy, mechanical and rheological properties of UHMWPE/LMWPE. Сompositions, including from 10 to 80 wt % UHMWPE with M_w = 160 kg mol^–1 (PE-160) were obtained in a two-stage process of ethylene polymerization with a metallocene catalyst. They differed in the order of introduction of PE-160 into UHMWPE (PE-160/UHMWPE and UHMWPE/PE-160). Compositions of UHMWPE and LMWPE with M_w = 48 kg mol^–1 (PE-48/UHMWPE) with PE-48 content from 6 to 30 wt % were synthesized in a single-stage polymerization of ethylene in the presence of a tandem catalyst. A comparison of the shape and size of particles of nascent polymer products was made using the SEM method. The morphology, tensile, dynamic mechanical and rheological properties of RPC have been studied depending on the method of their preparation, the content of the low molecular weight fraction, its molecular weight and physical and mechanical properties. An increase in the proportion of PE-160 and PE-48 in PE-160/UHMWPE and PE‑48/UHMWPE leads to an increase in RPC crystallinity, tensile modulus and dynamic mechanical modulus with significant deviations from the additivity rule.

Anisotropic magnetically active elastomers based on polydimethylsiloxane and magnetic particles of different chemical natures, shapes, and sizes have been synthesized. A comparative analysis of their mechanical properties (elastic modulus, strength, and elongation at break) has been performed depending on the mutual orientation of the internal structure, formed by magnetic filler particles during the synthesis of the composite in a magnetic field, and the direction of the external mechanical force applied to stretch the samples. The anisotropy of mechanical properties is most pronounced in composites based on anisometric particles, needle-like and plate-like. The highest values of anisotropy coefficient of elastic modulus are observed in the composite containing plate-like iron microparticles; for this composite, the ratio of the elastic moduli in the directions parallel and perpendicular to the internal structure reaches a value of five. The use of magnetic filler and its orientation by means of magnetic field is an effective method for creating polymer composites with anisotropy of mechanical properties.

A method for obtaining nonwoven carbon materials by the staged heat treatment of cellulose felt is developed. Fabrics produced from fibrous flax cellulose and viscose fibers by needle punching are used as nonwoven precursors. To obtain carbon fabric precursors the optimum ratios of components are chosen from the data on the formation of nonwoven fabrics and the thermal analysis of various blend formulations. It is shown that the content of flax fibers in the system should be at least 50%. Viscose fibers play the role of a reinforcing material and so far cannot be fully excluded from the system. With an increase in the content of flax cellulose the value of carbon yield grows. The mechanical properties of the carbon felt are provided by the physical network of friction and dispersion contacts between individual fibers. Upon heat treatment of the composite nonwoven material, the morphological features of precursor fibers remain unchanged. The interplanar distances of carbon layers in the carbon material are calculated using X-ray diffraction analysis and transmission electron microscopy. The fraction of carbon upon heat treatment to 1700°С is at least 90%, and after graphitization to 2400°С the purity of the product is above 99%. The maximum values of carbon yield at this temperature may be as high as 25‒27%. The coefficients of thermal conductivity of the carbon felt are measured, and the values obtained are 30% lower than the corresponding parameters of carbon fabrics.