Polymers

The four most popular water models in molecular dynamics were studied in large-scale simulations of Brownian motion of colloidal particles in optical tweezers and then compared with experimental measurements in the same time scale. We present the most direct comparison of colloidal polystyrene particle diffusion in molecular dynamics simulations and experimental data on the same time scales in the ballistic regime. The four most popular water models, all of which take into account electrostatic interactions, are tested and compared based on yielded results and resources required. Three different conditions were simulated: a freely moving particle and one in a potential force field with two different strengths based on 1 pN/nm and 10 pN/nm. In all cases, the diameter of the colloidal particle was 50 nm. The acquired data were compared with experimental measurements performed using optical tweezers with position capture rates as high as 125 MHz. The experiments were performed in pure water on polystyrene particles with a 1 μm diameter in special microchannel cells. Full article

Stimuli-responsive hydrogel actuators have attracted tremendous interest in switches and microrobots. Based on N-isopropylacrylamide (NIPAM) monomers with LCST phase separation and photochromic molecule spiropyran which can respond to ultraviolet light and H+, we develop a novel multistimuli-responsive co-polymer anisotropic bilayer hydrogel, which can undergo complex deformation behavior under environmental stimuli. Diverse bending angles were achieved based on inhomogeneous swelling. By controlling the environmental temperature, the bilayer hydrogels achieved bending angles of 83.4° and −162.4° below and above the critical temperature of PNIPAM. Stimulated by ultraviolet light and H+, the bilayer hydrogels showed bending angles of −19.4° and −17.3°, respectively. In addition, we designed a strategy to enhance the mechanical properties of the hydrogel via double network (DN). The mechanical properties and microscopic Fourier transform infrared (micro-FTIR) spectrum showed that the bilayer hydrogel can be well bonded at the interfaces of such bilayers. This work will inspire the design and fabrication of novel soft actuators with synergistic functions. Full article

The basic intention of the present work is to analyze the influence of the incorporated microporous membrane and the technology of the needling process on the functional properties of nonwovens designed as an insulating layer for protective gloves for protection against high temperatures. The investigated nonwovens are produced in carded nonwoven formation and mechanically bonded with needle bonding. The studied nonwovens contain a microporous membrane of polyester (PES) with a thickness of 20 µm (samples marked as ST and STL). In the theoretical part of the research work, the nonwovens and some technology stages are presented. The experimental part of the present work deals with the mechanical properties: breaking stress and strain, viscoelastic properties (yield strength, elastic modulus) and elastic recovery after cyclic loading and thermal conduction. In the experimental part, permeability properties (water vapor permeability, air permeability) are also analyzed. The results of the investigation show that the samples marked as ST and STL, which contain a microporous PES membrane, have a higher breaking stress than the samples marked as T and TL without the microporous PES membrane. Samples marked as ST and STL also exhibit higher values of elongation at break and limit of recoverable deformation (stress and strain at yield) and a lower modulus of elasticity than samples marked as T and TL. The samples marked as ST and STL are mechanically bonded to the lamellar plate using forked needles and therefore have a textured (ribbed) shape that affects the improved mechanical properties. The TL and STL samples, which contain a microporous PES membrane, have higher elastic recovery and lower air permeability than the T and TL samples, while water vapor permeability is lower only for the ST sample. Full article

Organic and perovskite semiconductor materials are considered an interesting combination thanks to their similar processing technologies and band gap tunability. Here, we present the design and analysis of perovskite/organic tandem solar cells (TSCs) by using a full optoelectronic simulator (SETFOS). A wide band gap lead-free ASnI₂Br perovskite top subcell is utilized in conjunction with a narrow band gap DPPEZnP-TBO:PC61BM heterojunction organic bottom subcell to form the tandem configuration. The top and bottom cells were designed according to previous experimental work keeping the same materials and physical parameters. The calibration of the two cells regarding simulation and experimental data shows very good agreement, implying the validation of the simulation process. Accordingly, the two cells are combined to develop a 2T tandem cell. Further, upon optimizing the thickness of the front and rear subcells, a current matching condition is satisfied for which the proposed perovskite/organic TSC achieves an efficiency of 13.32%, J_sc of 13.74 mA/cm², and V_oc of 1.486 V. On the other hand, when optimizing the tandem by utilizing full optoelectronic simulation, the tandem shows a higher efficiency of about 14%, although it achieves a decreased J_sc of 12.27 mA/cm². The study shows that the efficiency can be further improved when concurrently optimizing the various tandem layers by global optimization routines. Furthermore, the impact of defects is demonstrated to highlight other possible routes to improve efficiency. The current simulation study can provide a physical understanding and potential directions for further efficiency improvement for lead-free perovskite/organic TSC. Full article

A comprehensive experimental investigation of the noise evaluation of coated spur polymer gears made of POM was performed in this study. The three Physical Vapour Deposition (PVD) coatings investigated were aluminium (Al), chromium (Cr), and chromium nitrite (CrN). The gears were tested on an in-house-developed testing machine under a torque of 20 Nm and at a rotational speed of 1000 rpm. The noise measurements were performed with the tested gear pair on the testing device with a sound-proof acoustic foam used for the acoustic sound-proof insulation. The sound signal was analysed in time, frequency, and time–frequency domains and typical phenomena were identified in the signal. Experimental results showed that the noise level was higher for polymer gears with different coatings if compared to the polymer gears without coatings. With sound analysis in the time–frequency domain, precise degradation of the coatings could be noticed. In future studies, it would be appropriate to use a new method for signal analysis, e.g., high-order statistics and hybrid technique. Full article

Liposomes carry various compounds with applications in pharmaceutical, food, and cosmetic fields, and the administration route is especially parenteral, oral, or transdermal. Liposomes are used to preserve and release the internal components, thus maintaining the properties of the compounds, the stability and shelf life of the encapsulated products, and their functional benefits. The main problem in obtaining liposomes at the industrial level is their low stability due to fragile phospholipid membranes. To increase the stability of liposomes, phospholipid bilayers have been modified or different coating materials have been developed and studied, both for liposomes with applications in the pharmaceutical field and liposomes in the food field. In the cosmetic field, liposomes need no additional coating because the liposomal formulation is intended to have a fast penetration into the skin. The aim of this review is to provide current knowledge regarding physical and chemical factors that influence stability, coating materials for liposomes with applications in the pharmaceutical and food fields to increase the stability of liposomes containing various sensitive compounds, and absorption of the liposomes and commercial liposomal products obtained through various technologies available on the market. Full article

Osteoarthritis is a highly prevalent disease worldwide that leads to cartilage loss. Tissue engineering, involving scaffolds, cells, and stimuli, has shown to be a promising strategy for its repair. Thus, this study aims to manufacture and characterise different scaffolds with poly(ε-caprolactone) (PCL) with commercial cellulose (microcrystalline (McC) and methyl cellulose (MC) or cellulose from agro-industrial residues (corncob (CcC)) and at different percentages, 1%, 2%, and 3%. PCL scaffolds were used as a control. Morphologically, the produced scaffolds presented porosities within the desired for cell incorporation (57% to 65%). When submitted to mechanical tests, the incorporation of cellulose affects the compression resistance of the majority of scaffolds. Regarding tensile strength, McC2% showed the highest values. It was proven that all manufactured scaffolds suffered degradation after 7 days of testing because of enzymatic reactions. This degradation may be due to the dissolution of PCL in the organic solvent. Biological tests revealed that PCL, CcC1%, and McC3% are the best materials to combine with human dental pulp stem/stromal cells. Overall, results suggest that cellulose incorporation in PCL scaffolds promotes cellular adhesion/proliferation. Methyl cellulose scaffolds demonstrated some advantageous compressive properties (closer to native cartilaginous tissue) to proceed to further studies for application in cartilage repair. Full article

Development of natural protein-based hydrogels with self-healing performance and tunable physical properties has attracted increased attention owing to their wide potential not only in the pharmaceutical field, but also in wounds management. This work reports the development of a versatile hydrogel based on enzymatically-crosslinked gelatin and nanogels loaded with amoxicillin (Amox), an antibiotic used in wound infections. The transglutaminase (TGase)-crosslinked hydrogels and encapsulating nanogels were formed rapidly through enzymatic crosslinking and self-assembly interactions in mild conditions. The nanogels formed through the self-assemble of maleoyl-chitosan (MAC5) and polyaspartic acid (PAS) may have positive influence on the self-healing capacity and drug distribution within the hydrogel network through the interactions established between gelatin and gel-like nanocarriers. The physicochemical properties of the enzymatically-crosslinked hydrogels, such as internal structure, swelling and degradation behavior, were studied. In addition, the Amox release studies indicated a rapid release when the pH of the medium decreased, which represents a favorable characteristic for use in the healing of infected wounds. It was further observed through the in vitro and in vivo biocompatibility assays that the optimized scaffolds have great potential to be used as wound dressings. Full article

Gelatin usage in scaffold fabrication is limited due to its lack of enzymatic and thermal resistance, as well as its mechanical weakness. Hence, gelatin requires crosslinking and reinforcement with other materials. This study aimed to fabricate and characterise composite scaffolds composed of gelatin, elastin, and cellulose nanocrystals (CNC) and crosslinked with genipin. The scaffolds were fabricated using the freeze-drying method. The composite scaffolds were composed of different concentrations of CNC, whereas scaffolds made of pure gelatin and a gelatin–elastin mixture served as controls. The physicochemical and mechanical properties of the scaffolds, and their cellular biocompatibility with human dermal fibroblasts (HDF), were evaluated. The composite scaffolds demonstrated higher porosity and swelling capacity and improved enzymatic resistance compared to the controls. Although the group with 0.5% (w/v) CNC recorded the highest pore size homogeneity, the diameters of most of the pores in the composite scaffolds ranged from 100 to 200 μm, which is sufficient for cell migration. Tensile strength analysis revealed that increasing the CNC concentration reduced the scaffolds’ stiffness. Chemical analyses revealed that despite chemical and structural alterations, both elastin and CNC were integrated into the gelatin scaffold. HDF cultured on the scaffolds expressed collagen type I and α-SMA proteins, indicating the scaffolds’ biocompatibility with HDF. Overall, the addition of elastin and CNC improved the properties of gelatin-based scaffolds. The composite scaffolds are promising candidates for an acellular skin substitute. Full article

Polyurethane microcellular elastomers (PUME) are good at impact protection and energy absorption, and belong to rate sensitive- and strain history-dependent materials. In this study, PUME with different densities of 800 kg/m³, 600 kg/m³ and 400 kg/m³ were prepared, then the compressive responses of PUME in the strain rate range of 0.001 s⁻¹ to 3400 s⁻¹ were systemically investigated. By studying the energy absorption and efficiency diagram of PUME, the compressive properties of materials with different densities under compressive impact load were described, which showed that PUME with a density of 600 kg/m³ had better performance. A visco–hyperelasticity–air constitutive model was established to describe the large deformation response of PUME at high strain rates. The model included three components: hyperelastic part, viscoelastic part and gas pressure part. Quasi-static and dynamic compression tests were used to determine the constitutive relations of seven parameters. The samples with a density of 600 kg/m³ at different strain rates were fitted by MATLAB software, and the constitutive model parameters were obtained. The comparison between the constitutive equation and the experimental results showed that there was a good consistency. The constitutive model can provide data support for simulation analysis and application of PUME as energy absorbing protective facilities. Full article

Limbal stem cells (LSCs) are of paramount importance in corneal epithelial tissue repair. The cornea becomes opaque in case of limbal stem cell deficiency (LSCD), which may cause serious damage to the ocular visual function. There are many techniques to restore damaged epithelium, one of which is the transplantation of healthy cultured LSCs, usually onto a human amniotic membrane or onto bio-based engineered scaffolds in recent years. In this study, melt electrospun polylactic acid (PLA) was modified by silk fibroin or gelatin and further cultured with LSCs originating from three different donors. In terms of physicochemical properties, both modifications slightly increased PLA scaffold porosity (with a significantly larger pore area for the PLA/gelatin) and improved the scaffolds’ swelling percentage, as well as their biodegradation rate. In terms of the scaffold application function, the aim was to detect/visualize whether LSCs adhered to the scaffolds and to further determine cell viability (total number), as well as to observe p63 and CK3 expressions in the LSCs. LSCs were attached to the surface of microfibers, showing flattened conformations or 3D spheres in the formation of colonies or agglomerations, respectively. All scaffolds showed the ability to bind the cells onto the surface of individual microfibers (PLA and PLA/gelatin), or in between the microfibers (PLA/silk fibroin), with the latter showing the most intense red fluorescence of the stained cells. All scaffolds proved to be biocompatible, while the PLA/silk fibroin scaffolds showed the highest 98% viability of 2.9 × 10⁶ LSCs, with more than 98% of p63 and less than 20% of CK3 expressions in the LSCs, thus confirming the support of their growth, proliferation and corneal epithelial differentiation. The results show the potential of these bio-engineered scaffolds to be used as an alternative clinical approach. Full article

With a significant number of features (namely being multipurpose, inexpensive and durable), thermoplastic polymers, most often named plastics, are part of our daily routine, with an increasing production over the last decade. Among them, polyethylene terephthalate (PET), high-density polyethylene (HDPE) and polypropylene (PP) are distinguished as the five most commonly used plastics in various fields, mainly in the packaging industry. Even if it is difficult to imagine the world without plastics, the boosted plastic assembly comes with huge plastic waste, creating a number of challenges, as the most important threat for our environment, but also opportunities for recycling. Currently, a special attention is dedicated on how to improve the current recycling methods or to find new ones, since the quality of recycled plastics and potential chemical or biological contaminations are two problematic aspects. Understanding the properties of each thermoplastic polymer and the interaction with possible contaminants may be the key for an efficient recycling process. The aim of this paper was to evaluate the surface behaviour of different composite supports based on recycled PET before and after interaction with collagen (used as a biological contaminant). The surface contamination bias of PET supports was studied through different techniques: scanning electron microscopy (SEM), water uptake through swelling studies, contact angle measurements and attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR). Full article

Glyphosate (N-phosphonomethyl glycine) is a non-selective, broad-spectrum organophosphate herbicide. Its omnipresent application with large quantity has made glyphosate as a problematic contaminant in water. Therefore, an effective technology is urgently required to remove glyphosate and its metabolites from water. In this study, calcium peroxide nanoparticles (nCPs) were functioned as an oxidant to produce sufficient hydroxyl free radicals (·OH) with the presence of Fe²⁺ as a catalyst using a Fenton-based system. The nCPs with small particle size (40.88 nm) and high surface area (28.09 m²/g) were successfully synthesized via a co-precipitation method. The synthesized nCPs were characterized using transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), Brunauer–Emmett–Teller analysis (BET), dynamic light scattering (DLS), and field emission scanning electron microscopy (FESEM) techniques. Under the given conditions (pH = 3.0, initial nCPs dosage = 0.2 g, Ca²⁺/Fe²⁺ molar ratio = 6, the initial glyphosate concentration = 50 mg/L, RT), 99.60% total phosphorus (TP) removal and 75.10% chemical oxygen demand (COD) removal were achieved within 75 min. The degradation process fitted with the Behnajady–Modirshahla–Ghanbery (BMG) kinetics model. The H₂O₂ release performance and proposed degradation pathways were also reported. The results demonstrated that calcium peroxide nanoparticles are an efficient oxidant for glyphosate removal from aqueous systems. Full article

In recent years, China is increasingly dependent on imported wood. Afrormosia and Newtonia are some of the imported species with good utilization potential. However, both of them also have problems with poor dimensional stability. In order to make better use of these two types of wood, the influence of heat treatment under air and palm oil conditions on the color, dimensional stability, and hygroscopicity of Afrormosia and Newtonia was investigated. The Afrormosia and Newtonia wood samples were heated in air or palm oil medium for two hours at 160 °C, 180 °C and 200 °C, respectively. Then, the color, weight changes, swelling, moisture absorption and chemical structure were evaluated for each case. As results, the heat treatments with air or palm oil increased the dark color of Newtonia and Afrormosia wood and this increase was proportional to the treatment temperature. The tangential and radial swelling coefficient for air heat treatment of Afrormosia wood at 200 °C were, respectively, reduced by 24.59% and 19.58%, while this reduction for Newtonia was 21.32% and 14.80%. The heat treatment in palm oil further improved the stability and hygroscopicity of the wood, showing that the Afrormosia samples treated by palm oil at 200 °C underwent a decrease of its tangential and radial swelling coefficient, respectively, by 49.34% and 45.88%, whereas the tangential and radial swelling coefficient of Newtonia treated under the same conditions were reduced by 42.85% and 33.63%, respectively. The heat treatments of Afrormosia and Newtonia samples under air at 200 °C diminished the water absorption by 21.67% and 22.12%. The water absorption of Afrormosia and Newtonia heat-treated under palm oil at 200 °C was reduced, respectively, by 39.40% and 37.49%. Moreover, the FTIR analysis showed the decrease of hydroxyl groups in proportion to the wood treatment temperature. Full article

This study aims to elucidate the structure–property–process relationship of 3D printed polyamide and short carbon fibre-reinforced polyamide composites. The macroscopic properties (tensile modulus) of the 3D printed samples are quantitatively correlated to the printing process-induced intrinsic microstructure with multiple interfaces. The samples were printed with different layer thicknesses (0.1, 0.125 and 0.2 mm) to obtain the varied number of interface densities (number of interfaces per unit sample thickness). The result shows that the printed short carbon fibre-reinforced polyamide composites had inferior partially bonded interfaces compared to the printed polyamide, and consequently exhibited interface-dependent elastic performance. The tensile modulus of 3 mm thick composites decreased up to 18% as a function of interface density, whilst the other influencing aspects including porosity, crystallinity and fibre volume fraction (9%) were the same. Injection moulding was also employed to fabricate samples without induced interfaces, and their tensile properties were used as a benchmark. Predictions based on the shear-lag model were in close agreement (<5%) with the experimental data for the injection-moulded composites, whereas the tensile modulus of the printed composites was up to 38% lower than the predicted modulus due to the partial bonded interfaces. Full article

Interface properties between charge transport and perovskite light-absorbing layers have a significant impact on the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is a polyelectrolyte composite that is widely used as a hole transport layer (HTL) to facilitate hole transport from a perovskite layer to an anode. However, PEDOT:PSS must be modified using a functional additive because PSCs with a pristine PEDOT:PSS HTL do not exhibit a high PCE. Herein, we demonstrate an increase in the PCE of PSCs with a polyethylene glycol hexadecyl ether (Brij C10)-mixed PEDOT:PSS HTL. Photoelectron spectroscopy results show that the Brij C10 content becomes significantly high in the HTL surface composition with an increase in the Brij C10 concentration (0–5 wt%). The enhanced PSC performance, e.g., a PCE increase from 8.05 to 11.40%, is attributed to the reduction in non-radiative recombination at the interface between PEDOT:PSS and perovskite by the insulating Brij C10. These results indicate that the suppression of interface recombination is essential for attaining a high PCE for PSCs. Full article

In this study, a green chemistry method was used to synthesize polymer composites based on polyethylene oxide (PEO). The method of the remediation of metal complexes used in this study is an environmentally friendly procedure with a low cost. Zinc metal ion (Zn²⁺)-polyphenol (PPHNL) complexes were synthesized for two minutes via the combination of a black tea leaf (BTL) extract solution with dissolved Zn-acetate. Then, UV–Vis and FTIR were carried out for the Zn-PPHNL complexes in a liquid and solid. The FTIR spectra show that BTLs contain sufficient functional groups (O-H, C-H, C=O, C=C, C-O, C-N, and N-H), PPHNL, and conjugated double bonds to produce metal complexes by capturing the cations of Zn-acetate salt. Moreover, FTIR of the BTL and Zn–PPHNL complexes approves the formation of the Zn-PPHNL complex over the wide variation in the intensity of bands. The UV absorption spectra of BTL and Zn-PPHNL indicate complex formation among tea PPHNL and Zn cations, which enhances the absorption spectra of the Zn-PPHNL to 0.1 compared to the figure of 0.01 associated with the extracted tea solution. According to an XRD analysis, an amorphous Zn-PPHNL complex was created when Zn²⁺ ions and PPHNL interacted. Additionally, XRD shows that the structure of the PEO composite becomes a more amorphous structure as the concentration of Zn-PPHNL increases. Furthermore, morphological study via an optical microscope (OM) shows that by increasing the concentration of Zn-PPHNL in a PEO polymer composite the size of the spherulites ascribed to the crystalline phase dramatically decreases. The optical properties of PEO: Zn-PPHNL films, via UV–Vis spectroscopy, were rigorously studied. The E_g is calculated by examining the dielectric loss, which is reduced from 5.5 eV to 0.6 eV by increasing the concentration of Zn-PPHNL in the PEO samples. In addition, Tauc’s form was used to specify the category of electronic transitions in the PEO: Zn-PPHNL films. The impact of crystalline structure and morphology on electronic transition types was discussed. Macroscopic measurable parameters, such as the refractive index and extinction coefficient, were used to determine optical dielectric loss. Fundamental optical dielectric functions were used to determine some key parameters. From the viewpoint of quantum transport, electron transitions were discussed. The merit of this work is that microscopic processes related to electron transition from the VB to the CB can be interpreted interms of measurable macroscopic quantities. Full article

An amphiphilic diblock copolymer (PChM-PNIPAM), composed of poly(cholesteryl 6-methacryloyloxy hexanoate) (PChM) and poly(N-isopropyl acrylamide) (PNIPAM) blocks, was prepared via reversible addition–fragmentation chain transfer radical polymerization. The PChM and PNIPAM blocks exhibited liquid crystalline behavior and a lower critical solution temperature (LCST), respectively. PChM-PNIPAM formed water-soluble polymer micelles in water below the LCST because of hydrophobic interactions of the PChM blocks. The PChM and PNIPAM blocks formed the core and hydrophilic shell of the micelles, respectively. With increasing temperature, the molecular motion of the pendant cholesteryl groups increased, and a liquid crystalline phase transition occurred from an amorphous state in the core. With further increases in temperature, the PNIPAM block in the shell exhibited the LCST and dehydrated. Hydrophobic interactions of the PNIPAM shells resulted in inter-micellar aggregation above the LCST. Full article

With the assessment of intermediate crack debonding (ICD) being a subject of main importance in the design of reinforced concrete (RC) beams strengthened in flexure with externally bonded fibre-reinforced polymer (FRP), several approaches to predict the debonding loads have been developed in recent decades considering different models and strategies. This study presents an analysis of formulations with different levels of approximation collected in the fib Bulletin 90 regarding this failure mode, comparing the theoretical predictions with experimental results. The carried-out experiments consisted of three RC beams strengthened with carbon FRP (CFRP) tested under a four-point bending configuration with different concrete strengths and internal steel reinforcement ratios. With failure after steel yielding, higher concrete strength, as well as a higher reinforcement ratio, lead to a higher bending capacity. In addition, the performance of the models is assessed through the experimental-to-predicted failure load ratios from an experimental database of 65 RC beams strengthened with CFRP gathered from the literature. The results of the comparative study show that the intermediate crack debonding failure mode is well predicted by all models with a mean experimental-to-predicted failure load ratio between 0.96 and 1.10 in beams tested under three- or four-point bending configurations. Full article