Search Results (192)

Poly(vinyl chloride) (PVC) undergoes thermal degradation during processing and operation, which necessitates the use of effective thermal stabilizers. The purpose of this work is to comprehensively evaluate the potential of new hierarchically structured titanium phosphates (TiP) with controlled morphology as thermal stabilizers of plasticized PVC, focusing on the effect of morphology and Ti/P ratio on their stabilizing efficiency. The thermal stability of the compositions was studied by thermogravimetric analysis (TGA) in both inert (Ar) and oxidizing (air) atmospheres. The effect of TiP concentration and its synergy with industrial stabilizers was analyzed. An assessment of the key degradation parameters is given: the temperature of degradation onset, the rate of decomposition, exothermic effects, and the carbon residue yield. In an inert environment, TiPMSI/TiPMSII microspheres demonstrated an optimal balance by increasing the temperature of degradation onset and the residual yield while suppressing the rate of decomposition. In an oxidizing environment, TiPR rods and TiPMSII microspheres provided maximum stability, enhancing resistance to degradation onset and reducing the degradation rate by 10–15%. Key factors of effectiveness include ordered morphology (spheres, rods); the Ti-deficient Ti/P ratio (~0.86), which enhances HCl binding; and crystallinity. The stabilization mechanism of titanium phosphates is attributed to their high affinity for hydrogen chloride (HCl), which catalyzes PVC chain scission, a catalyst for the destruction of the PVC chain. The unique microstructure of titanium phosphate provides a high specific surface area and, as a result, greater activity in the HCl neutralization reaction. The formation of a sol–phosphate framework creates a barrier to heat and oxygen. An additional contribution comes from the inhibition of oxidative processes and the possible interaction with unstable chlorallyl groups in PVC macromolecules. Thus, hierarchically structured titanium phosphates have shown high potential as multifunctional PVC thermostabilizers for modern polymer materials. Potential applications include the development of environmentally friendly PVC formulations with partial or complete replacement of toxic stabilizers, the optimization of thermal stabilization for products used in aggressive environments, and the use of hierarchical TiP structures in flame-resistant and halogen-free PVC-based compositions. Full article

Supercapacitors, with their remarkable attributes such as including a high power density, an extended cycle life, and inherent safety, have emerged as a major research area for electrochemical energy storage. In this paper, phenylenediamine and glyoxal were used as raw material to prepare p-phenylenediamine glyoxal (PGo) with one single step. p-phenylenediamine glyoxal-ferrocene (PGo-Fc_x, x = 1, 0.3, 0.2, 0.1) composites were synthesized based on a poly-Schiff base. FTIR and XRD results indicated that ferrocene doping preserves the intrinsic PGo framework while inducing grain refinement, as evidenced by the narrowing of the XRD diffraction peaks. SEM observations further revealed distinct morphological evolution. CV (cyclic voltammetry), EIS (electrochemical impedance spectroscopy), and GCD (galvanostatic charge–discharge) were conducted on PGo-Fc_x in order to examine its electrochemical performance. The PGo-Fc_0.3 in PGo-Fc_x electrode material had a specific capacitance of 59.6 F/g at a current density of 0.5 A/g and 36 F/g at a current density of 10 A/g. Notably, even after undergoing 5000 charging–discharging cycles at 10 A/g, the material retained 76.2% of its specific capacitance compared to the initial cycle. Therefore, taking conductive polymers and metal oxide materials for modification can improve the stability and electrochemical performance of supercapacitors. Full article

As part of a systematic study on the structures of the mixed halide isothiocyanates, Sn^IIHal(NCS), their single crystals were grown and structurally characterized. For Hal = F (1), the SnClF structure type was confirmed, while with Hal = Cl (2), Br (3), and I (4), there are three isostructural compounds of a new structure type, and for Hal = Cl (5), there is a second modification of a third structure type. These structure types have been described with respect to the composition and coordination geometry of the first, second, and van der Waals crust coordination spheres and their dependence on the halogen size and thiocyanate binding modes. With respect to the first coordination spheres, all three structure types constitute one-dimensional coordination polymers. In 1, “ladder”-type double chains result from μ₃-bridging fluorine atoms, and in 2–4, single-chains built up from μ₂-halogen atoms are pairwise “zipper”-like interconnected via κ²NS-bridging NCS ligands, which manage the halogen-linked chain assembly in the double chains of 5. Based on the octet rule, short atom distances are interpreted in terms of 2c-2e and various (symmetrical, quasi-symmetrical, and asymmetrical) kinds of 3c-4e bonds. Weak contacts, the topology of which suggests the extension of the latter bonding concept, are identified as electron-deficient, bifurcated tetrel bonds. Full article

We conduct extensive Monte Carlo simulations to investigate the factors that control the isotropic-to-nematic transition of hard colloidal polymers in bulk and under various conditions of confinement. Utilizing a highly idealized model, polymers are represented as linear chains of tangent hard spheres of uniform length, whose stiffness is controlled by a bending potential leading to rod-like configurations. Confinement is realized through the presence of flat, parallel, and impenetrable walls in one, two, or three dimensions while periodic boundary conditions are applied on the unconstrained dimensions. All simulations are performed through the Simu-D software, composed of conventional and advanced, chain-connectivity-altering Monte Carlo algorithms. We explore in detail how distinct factors, including chain length, stiffness, confinement, and packing density affect the isotropic-to-nematic transition exhibited by the polymer chains and identify with high precision the concentration range where this phase change takes place as a function of the applied conditions. Full article

Alginate hydrogels offer distinct advantages as ionically crosslinked, biocompatible networks that can be shaped into spherical beads with high compositional flexibility. These spherical architectures provide isotropic geometry, modularity and the capacity for encapsulation, making them ideal platforms for scalable, stimuli-responsive actuation. Their ability to respond to thermal, magnetic, electrical, optical and chemical stimuli has enabled applications in targeted delivery, artificial muscles, microrobotics and environmental interfaces. This review examines recent advances in alginate sphere-based actuators, focusing on fabrication methods such as droplet microfluidics, coaxial flow and functional surface patterning, and strategies for introducing multi-stimuli responsiveness using smart polymers, nanoparticles and biologically active components. Actuation behaviours are understood and correlated with physical mechanisms including swelling kinetics, photothermal effects and the field-induced torque, supported by analytical and multiphysics models. Their demonstrated functionalities include shape transformation, locomotion and mechano-optical feedback. The review concludes with an outlook on the existing limitations, such as the material stability, cyclic durability and integration complexity, and proposes future directions toward the development of autonomous, multifunctional soft systems. Full article

Industrial textile wastewater containing both heavy metals and dyes has been massively produced. In this study, semi-interpenetrating polymer network structures of sodium alginate (SA)/polyvinyl alcohol (PVA)/κ-carrageenan (CG) aerogel beads were synthesized for their simultaneous reduction. The SA/PVA/CG aerogel beads were synthesized through a cost-effective and environmentally friendly method using naturally abundant biopolymers without toxic cross-linkers. The SA/PVA/CG aerogel beads were spheres with a size of 3.8 $\pm$ 0.1 mm, exhibiting total pore areas of 15.2 m²/g and porous structures (pore size distribution: 0.04–242.7 μm; porosity: 93.97%) with abundant hydrogen bonding, high water absorption capacity, and chemical resistance. The adsorption capacity and mechanisms of the SA/PVA/CG aerogel beads were investigated through kinetic and isotherm experiments for heavy metals (Cu(II), Pb(II)), cationic dye (methylene blue, MB), and anionic dye (acid blue 25, AB)) in both single and binary systems. The maximum adsorption capacities of the SA/PVA/CG aerogel beads based on the Langmuir model of Cu(II), Pb(II), and MB were 85.17, 265.98, and 1324.30 mg/g, respectively. Pb(II) showed higher adsorption affinity than Cu(II) based on ionic properties, such as electronegativity and hydration radius. The adsorption of Cu(II), Pb(II), and MB on the SA/PVA/CG aerogel beads was spontaneous, with heavy metals and MB exhibiting endothermic and exothermic natures, respectively. Full article

Three new coordination polymers, {[M(nbpdc)(DMF)(H₂O)₂]·H₂O}_∞ (M = Co and Ni) and [Zn(nbpdc)(DMF)(H₂O)]_∞, were synthesized from 2-nitrobiphenyl-4,4′-dicarboxylate (nbpdc²⁻). The isomorphous Co(II) and Ni(II) compounds exhibited a two-dimensional coordination network in which the chains with single-water bridges and the chains with single-nbpdc²⁻ bridges intersected each other by sharing the metal ions. The coordination networks were connected with uncoordinated water molecules through hydrogen bonds. The rarely identified single-water-bridged coordination chain was reinforced by water-based intrachain hydrogen bonds. The single-water bridges mediated modest antiferromagnetic superexchange in both Co(II) and Ni(II) compounds and afforded a spin-canting structure for the Co(II) compound at low temperatures. Water molecules played a distinct structural role in the Zn(II) compound, which was a one-dimensional coordination polymer with single-nbpdc²⁻ bridges. Instead of bridging metal ions, each water molecule was coordinated to one metal ion and hydrogen-bonded to the coordination spheres of other two metal ions, resulting to an infinite ladderlike hydrogen-bonding motif. The ladders interlinked the nbpdc-bridged chains into a three-dimensional supramolecular architecture featuring the 5-conneted {4⁴.6⁴} net. Full article

Polymer materials are increasingly used in all spheres of human activity. Today, it is difficult to imagine our life without the use of polymer products. Polymers have played a crucial role in the development of many industries and, of course, can be considered as one of the main drivers of technological progress. The research on the creation of new polymer materials that are obtained by modifying known polymers with various fillers, including nanomaterials, is widespread nowadays. In the foreseeable future, the time will come for modified polymer composites, when up to 75% of all things and materials that surround us will contain nano-additives. Due to their unique properties, these polymer compounds are in demand not only in industry and in everyday life, but also in medicine. One well-known nanomaterial is carbon nanotubes. The existing applications of nanotubes are almost limitless. Using them as modifying additives, it is possible to improve the properties of almost all known materials: polymers, alloys, plastics, rubbers, concretes, etc. In this review paper, the well-known polymer polypropylene and carbon nanotubes are selected as the main subjects of this study. This choice is due to their high demand in medicine, electronics, construction, etc. Full article

In this work, the influence of surface functionalization due to synthesis conditions of graphene oxide quantum dots GOQDs was evaluated for dopamine (DA) detection. GOQDs were synthesized using HNO₃ (6 M or 8 M) through a liquid-phase oxidation method. The characterization (HRTEM, FTIR, Raman, and XRD) and evaluation by amperometry (AMP) and differential pulse voltammetry (DPV) showed that GOQDs-8 synthesized with higher oxygen content were more sensitive and selective in DA detection than GOQDs-6. The synergistic effects of electrostatic attraction from glassy carbon electrode negatively charged surface, functionalization for inner-sphere mechanism, and edge effect from lower particle size resulted in amplified electrochemical signal achieving detection at nanomolar level using AMP and DPV. When evaluated using AMP, GCE/GOQDs-8 showed a sensitivity of 0.0422 μA μM^–1, a limit of detection (LOD) of 17.6 nM, a linear range from 0.1 to 100 μM, and minimal interference for uric acid, levodopa, and acetaminophen. In contrast, using DPV, the GCE/GOQDs-8 exhibited a sensitivity of 0.0616 μA μM^–1, a LOD of 506 nM, and a linear range from 0.1–30 μM with remarkable selectivity from all interferent species. The assay of GOQDs-8/GCE sensor in normal human serum proved to be feasible for the practical determination of DA. The recovery obtained was in the range of 94.1 to 112.8% with a relative standard deviation (RSD), n = 3 of less than 3.62%. The oxygen-rich material showed a promising performance that can be further improved with additional nanocarbon or conducting polymers supports. Full article

The kinetic stability provided by the sterically demanding {SiN^Dipp}²⁻ dianion (SiN^Dipp = {CH₂SiMe₂NDipp}₂; Dipp = 2,6-i-Pr₂C₆H₃) is intrinsic to the isolation of not only the group 1 alumanyl reagents ([{SiN^Dipp}AlM]₂; M = K, Rb, Cs) but also facilitates the completely selective oxidative addition of a C-H bond of 1,2-C₂B₁₀H₁₂ to the aluminium centre. In each case, the resultant compounds comprise a four-coordinate o-carboranyl (hydrido)aluminate anion, [(SiN^Dipp)Al(H)(1,2-C₂B₁₀H₁₁)]⁻, in which the carboranyl cage is bonded to aluminium by an Al-C σ bond. Although the anions further assemble as extended network structures based on Al-H∙∙∙M, B-H∙∙∙M, and C-H∙∙∙M interactions, each structure is unique due to the significant variation in M⁺ ionic radius as group 1 is descended. The potassium derivative crystallises as a one-dimensional polymer, its rubidium analogue is a dimer due to the polyhapto-sequestration of a molecule of benzene solvent within the alkali metal coordination sphere, and the caesium species is a two-dimensional assembly of hexameric aggregates. Full article

Microbial fuel cells (MFCs) are a candidate for green energy sources due to microbes’ ability to generate charge in their metabolic processes. The main problem in MFCs is slow charge transfer between microorganisms and electrodes. Several methods to improve charge transfer have been used until now: modification of microorganisms by conductive polymers, use of lipophilic mediators, and conductive nanomaterials. We created an MFC with a graphite anode, covering it with 9,10-phenatrenequinone and polypyrrole-modified Saccharomyces cerevisiae with and without 10 nm sphere gold nanoparticles. The MFC was evaluated using cyclic voltammetry and power density measurements. The peak current from cyclic voltammetry measurements increased from 3.76 mA/cm² to 5.01 mA/cm² with bare and polypyrrole-modified yeast, respectively. The MFC with polypyrrole- and nanoparticle-modified yeast reached a maximum power density of 150 mW/m² in PBS with 20 mM Fe(III) and 20 mM glucose, using a load of 10 kΩ. The same MFC with the same load in wastewater reached 179.2 mW/m². These results suggest that this MFC configuration can be used to improve charge transfer. Full article

The formulation process for some drugs can be challenging, due to their unfavorable physical and mechanical properties and poor water solubility. Powder technology has made a significant impact in regard to the modification of the particles in active pharmaceutical ingredients (APIs) to produce high-quality granules. Spherical particles are preferred over other shapes, due to their high tap and bulk density, reduced dustiness, better flowability, strong anti-caking properties, and better mechanical performance during tableting. The present study investigates the possibility of obtaining spherical crystals of ceritinib, a drug used for the treatment of anaplastic lymphoma kinase (ALK)-positive advanced non-small cell lung cancer, which belongs to BCS class IV drugs and has a platy crystal shape. Ceritinib spheres were prepared by spherical agglomeration, in a ternary system, and quasi-emulsion solvent diffusion, with the addition of polyvinylpyrrolidone, as well as a combination of these two methods. With the combined method of spherical crystallization, crystals with the most favorable morphology and the narrowest distribution of particle sizes were obtained, which was the reason for further optimization. The influence of different impeller geometries and mixing rates on the morphology of the obtained crystals was examined and the optimal conditions for the process were selected. Using empirical correlations and a visual criterion, the process was scaled up from a 0.1 L to a 1 L batch crystallizer. The obtained crystals were characterized by light and scanning electron microscopy. The addition of a bridging liquid and/or a polymer additive did not change the internal structure of the ceritinib crystals, which was confirmed by X-ray powder diffraction. Full article

A new aluminum complex (NSO)AlMe₂ featuring a hydrogen bond donor on the ligand backbone has been synthesized via the reaction of AlMe₃ with 1-((2-(isopropylamino)phenyl)thio)propan-2-ol (NSO-H) and spectroscopically characterized. In the complex, the aluminum atom is in a distorted tetrahedral coordination sphere determined by the anionic oxygen and neutral nitrogen atoms of the ligand and by the two carbon atoms of the alkyl groups. After proper activation, the complex (NSO)AlMe₂ was able to promote the ring-opening polymerization of L-, rac-lactide, ε-caprolactone and rac-β-butyrolactone. The polymerization of rac-lactide was faster than that of L-lactide: in a toluene solution at 80 °C, the high monomer conversion of 100 equivalents was achieved in 1.5 h, reaching a turnover frequency of 63 mol_LA·mol_Al^–1·h^–1. The experimental molecular weights of the obtained polymers were close to those calculated, assuming the growth of one polymer chain for one added alcohol equivalent and the polydispersity indexes were monomodal and narrow. The kinetic investigation of the polymerization led to the determination of the apparent propagation constants and the Gibbs free energies of activation for the reaction; the terminal groups of the polymers were also identified. The complex (NSO)AlMe₂ was active in harsh conditions such as at a very low concentration or in the melt using technical-grade rac-lactide. A relatively high level of activity was observed in the ring-opening polymerization of ε-caprolactone and rac-β-butyrolactone. DFT calculations were performed and revealed the central role of the NH function of the coordinated ligand. Acting as a hydrogen bond donor, it docks the monomer in the proximity of the metal center and activates it toward the nucleophilic attack of the growing polymer chain. Full article

The use of Fused Filament Fabrication (FFF) of high-performance polymers is becoming increasingly prevalent, leading to the exploration of new applications. The use of such materials in critical cases for aerospace applications necessitates the verification of industry standards, particularly with regard to the requirements for part porosity. The authors investigate the effect of nozzle diameter and cooling temperature printing parameters on the porosity of the part by using existing modelling methods based on the sintering of cylinders and spheres and comparing the results to microscope snapshots of sections of parts. The models are able to be used as limits for predicting the longitudinal neck growth of the part. The authors show through experiments that the value of the cooling temperature of the deposited filament has a minimal effect on the outcome, while nozzle diameter has a strong impact on the resulting porosity. The modelling results show that there is a significant impact of both the nozzle diameter and cooling temperature on the porosity of the part. This implies that further refinement of the models is needed for the resulting parts to be applied in critical structures. Full article

The utilization of sheet structure composites as a viable conductive filler has been implemented in polymer-based electromagnetic shielding materials. However, the development of an innovative sheet structure to enhance electromagnetic shielding performance remains a significant challenge. Herein, we propose a novel design incorporating silver-modified nanosheet self-assembled hollow spheres to optimize their performance. The unique microporous structure of the hollow composite, combined with the self-assembled surface nanosheets, facilitates multiple reflections of electromagnetic waves, thereby enhancing the dissipation of electromagnetic energy. The contribution of absorbing and reflecting electromagnetic waves in hollow nanostructures could be attributed to both the inner and outer surfaces. When multiple reflection attenuation is implemented, the self-assembled stack structure of nanosheets outside the composite material significantly enhances the occurrence of multiple reflections, thereby effectively improving its shielding performance. The structure also facilitates multiple reflections of incoming electromagnetic waves at the internal and external interfaces of the material, thereby enhancing the shielding efficiency. Simultaneously, the incorporation of silver particles can enhance conductivity and further augment the shielding properties. Finally, the optimized Ag/NiSi-Ni nanocomposites can demonstrate superior initial permeability (2.1 × 10⁻⁶ H m⁻¹), saturation magnetization (13.2 emu g⁻¹), and conductivity (1.2 × 10⁻³ Ω•m). This work could offer insights for structural design of conductive fillers with improved electromagnetic shielding performance. Full article