Search Results (88)

Dye-sensitized solar cells (DSSCs) have emerged as a promising technology for converting sunlight into electricity at a low cost; however, it is still necessary to find a photostable, low-cost, and efficient photosensitizer. In this sense, the natural product bixin (Dye 1) has previously been reported as a potential photosensitizer. Thus, the present work reports the full synthesis of diester and diacid hybrids (Dyes 2 and 3, respectively, with corresponding yields of 93% and 52%) using the natural product bixin as a starting material and 1,3,4-oxadiazole ring as a connected point. The hydrolysis step of Dye 2 aims to obtain Dye 3 with a structural capacity to anchor the titanium dioxide (TiO₂) nanofilms via the carboxylic acid group. Both compounds (Dyes 1 and 3) can be adsorbed via pseudo-first order on the surface of TiO₂ nanofilms, reaching saturation after 10 and 6 min of exposure in an organic solution (1 × 10⁻⁵ M), respectively, with adsorption kinetics of the semisynthetic compound almost twofold higher than the natural product. Contrary to expectations, Dye 3 had spectral behavior similar to Dye 1, but with better frontier molecular orbital (FMO) parameters, indicating that Dye 3 will probably behave very similarly or have slightly better photovoltaic performance than Dye 1 in future DSSC measurements. Full article

The functionalisation of lignin-derived phenolics (guaiacol, 4-propylguaiacol, eugenol, isoeugenol, phenol, m-cresol, catechol, syringol, syringaldehyde, and vanillin) for the synthesis of thermoplastic polyurethanes (PUs) and polyester (PE) resins is herein described. Diols were synthesised from phenolics in a one-step reaction using either glycerol carbonate or ethylene carbonate as a greener, solvent-free synthetic route. Nine of the diols were selected for the synthesis of Pus, and two of the diols were used for the synthesis of PE resins, with their physical and thermal properties characterised. Analysis of the PUs by differential scanning calorimetry (DSC) confirmed their amorphous nature, while thermogravimetric analysis (TGA) suggested improved thermal stability for all PUs with the addition of an alkyl or aldehyde substituent on the benzene ring regardless of the diisocyanate used. However, lower PU thermal stabilities were observed with the use of an aliphatic diisocyanate over an aromatic diisocyanate in the absence of an additional substituent. Analysis of the PEs by DSC also confirmed that the clear resins were all amorphous, and gel permeation chromatography (GPC) revealed significantly higher molecular weights and dispersities when an aliphatic diacid was utilised over an aromatic diacid. Full article

Heavy metal pollution is a growing public health concern owing to rising environmental pollution throughout the world. The situation is more vulnerable in Bangladesh; therefore, this study assessed contamination levels in different land use categories such as rural, local market, industrial, research, and coastal areas, as well as the related health risks for farmers in Bangladesh. A total of 45 soil samples were considered from three depths (0–5 cm, 5–10 cm, and 10–15 cm) across five different areas, with three replications per depth, following the monsoon season. Samples were prepared using a diacid mixture, and heavy metals (Cu, Ni, Mn, Cr, Zn, Pb) were investigated using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Health risks were evaluated using standard assessment models. The results showed that coastal agricultural soils had the highest heavy metal concentrations (except Pb), while rural areas had the lowest (except Cu and Ni), with no clear depth-based pattern. Two contamination sources were identified: component 1 (Cu, Ni, Mn, Cr, Zn) and component 2 (Pb, Zn), indicating mixed and anthropogenic sources, respectively. The Pollution Load Index (PLI) was highest in coastal areas and lowest in rural areas. The average daily intake of metals followed the order of inhalation > dermal > ingestion, with inhalation being the primary exposure route. The highest cumulative cancer risk (CCR) was observed in coastal agricultural soils (5.82 × 10⁻⁹), while rural soils had the lowest CCR (8.24 × 10⁻¹⁰), highlighting significant regional differences in health risks. Full article

Human–computer interaction (HCI) enables communication between humans and computers, which is widely applied in various fields such as consumer electronics, education, medical rehabilitation, and industrial control. Human motion monitoring is one of the most important methods of achieving HCI. In the present work, a novel human motion monitoring sensor for contact touch and gesture recognition is fabricated based on polyester elastomer (PTE) synthesized from diols and diacids, with both piezoelectric and triboelectric properties. The PTE sensor can respond to contacted and contactless me-chemical signals by piezoelectric and triboelectric responding, respectively, which enables simultaneous touch control and gesture recognition. In addition, the PTE sensor presents high stretchability with elongation at break over 1000% and high durability over 4000 impact cycles, offering significant potential for consumer electronics and wearable devices. Full article

The rational design of ordered chromogenic supramolecular polymeric systems is critical for the advancement of next-generation stimuli-responsive, optical, and semiconducting materials. Previously, we reported the design of a stimuli-responsive, lamellar self-assembled platform composed of an imidazole-appended perylene diimide of varying methylene spacer length (n = 3, 4, and 6) and a commercially available diacid-functionalized diacetylene monomer, 10, 12 docosadiynedioic acid, in a 1:1 molar ratio. Herein, we expound on the importance of the composition of the imidazole-appended perylene diimide of varying methylene spacer length (n = 3, 4, and 6) and 10, 12 docosadiynedioic acid in the ratio of 2:1 to the supramolecular self-assembly, final morphology, and properties. Topochemical polymerization of the drop-cast films by UV radiation yielded blue-phase polydiacetylene formation, and subsequent thermal treatment of the films produced a thermoresponsive blue-to-red phase transformation. Differential scanning calorimetry (DSC) studies revealed a dual dependence of the methylene spacer length and stimuli treatment (UV and/or heat) on the thermal transitions of the films. Furthermore, small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) showed well-defined hierarchical semiconducting nanostructures with interconnected “chessboard”-patterned lamellar stacking. Upon doping with an ionic liquid, the 2:1 platform showed higher ionic conductivity than the previous 1:1 one. The results presented here illustrate the importance of the composition and architecture to the ionic domain connectivity and ionic conductivity, which will have far-reaching implications for the rational design of semiconducting polymers for energy applications including fuel cells, batteries, ion-exchange membranes, and mixed ionic conductors. Full article

New aromatic co-polyamide-imides (coPAIs) containing both carboxyl and hydroxyl groups in the repeating units were synthesized for the first time. Transport, thermal and morphological properties of dense nonporous membranes from PAIs obtained using the diacid chloride of 2-(4-carboxyphenyl)-1,3-dioxoisoindoline-5-carboxylic acid and diamines 5,5′-methylene-bis (2-aminophenol)) and 3,5-Diaminobenzoic acid, taken in molar ratios of 7:3, 1:1, and 3:7, have been studied. High levels of membrane permeability accompanied by high selectivity for mixtures of liquids with significantly different polarities were determined by realization of intra- and intermolecular interactions in polymer, which was proved by thermal analyses and hydrodynamic characteristics of coPAIs. This effect is discussed in the context of the effectiveness of intermolecular interactions between polymer chains containing carboxyl and hydroxyl functional groups. Full article

Polyester-based advanced thin films have versatile industrial applications, especially in the fields of textiles, packaging, and electronics. Recent advances in polymer science and engineering have resulted in the development of advanced amorphous and semi-crystalline polyesters with exceptional performance compared to those of conventional polymeric films. Among these, 1,4-cyclohexanedimethanol (CHDM) and cyclic-monomer-based polyesters have gained considerable attention for their exceptional characteristics and potential applications in smart films. This review article provides a comprehensive overview of the recent advances in the synthesis, characterization, and applications of CHDM and cyclic-monomer-based advanced polymers for smart film applications. It discusses the structure–property relationships of these innovative polyesters and highlights their unique characteristics, including thermal, mechanical, and barrier characteristics. Furthermore, this article also emphasizes the solution, melt, and solid-state polymerizations of the polymers. Special emphasis is placed on the influence of the addition of a second diol or second diacid on the performance characteristics of synthesized polyesters/copolyesters to explore their versatile industrial applications. Additionally, the impact of the stereochemistry of the monomers is explored to optimize the characterization of polyesters suitable for industrial applications. Furthermore, this article explores the potential of these advanced polyesters to be considered as materials for smart film applications, especially in the field of flexible electronics. Finally, this article examines the challenges and future recommendations for the development of CHDM and cyclic-monomer-based polyesters for smart film applications. It discusses potential avenues for further research, including in-depth studies for the synthesis and characterization of polyesters, the development of sustainable and biodegradable alternatives to cyclic monomers, alternative green approaches for the synthesis of polymers, etc. This review article provides valuable insight for researchers in academia and industry who are working in the fields of polymer science and materials engineering. Full article

Chitosan was subjected to a crosslinking reaction with three polyhydroxylated diacids (glucaric (GlcA), mannaric (ManA), and mucic (MucA) acids) that only differ in the spatial orientation of their hydroxyl groups. This work aimed to obtain experimental evidence of the impact of the three-dimensional arrangement of the crosslinkers on the resulting properties of the products. In all the cases, the products were hydrogels, and their chemical structures were fully elucidated by FT-IR spectroscopy and conductometric titration. Thermogravimetric and morphological studies were also carried out. The specific surface area of all the products was similar and higher than that of native chitosan. Moreover, all hydrogels were characterized in terms of viscoelastic properties and long-term stability under external perturbation. Furthermore, their lead adsorption efficiency and swelling capacity were assessed. Despite the resemblant chemical structure in all the hydrogels, Ch/ManA exhibited the highest lead adsorption capacity, (Ch/ManA: 93.8 mg g⁻¹, Ch/GlcA: 82.9 mg g⁻¹, Ch/MucA: 79.2 mg g⁻¹), while Ch/GlcA exhibited a remarkably higher swelling capacity (i.e., ~30% more than Ch/MucA and ~40% more than Ch/ManA). The results obtained herein evidenced that the selection of the polyhydroxylated crosslinker with the appropriate three-dimensional structure could be crucial to finely adjust the final materials’ features. Full article

The application of polyesters as food contact materials is an alternative to epoxy resin coatings, which can be a source of endocrine migrants. By using high-pressure liquid chromatography/electrospray ionization–mass spectrometry (HPLC/ESI-MS) with cone voltage-induced fragmentation in-source, a number of polyester-derived migrants were detected in the extracts of inner coatings of metallic cans. The polyester-derived migrants were detected in each inner coating of fish product-containing cans (5/5) and in one inner coating of meat product-containing can (1/5). They were not detected in the inner coatings of vegetable/fruit product-containing cans (10 samples). The respective detected parent and product ions enabled differentiation between cyclic and linear compounds, as well as unambiguous identification of diol and diacid units. Most of the detected compounds, cyclic and linear, were composed of neopentyl glycol as diol and two diacid comonomers, namely isophthalic acid and hexahydrophthalic acid. The other detected oligoesters were composed of neopentyl glycol or propylene glycol and adipic acid/isophthalic acid as comonomers. The compounds containing propylene glycol as diol were found to be exclusively linear cooligoesters. On the basis of abundances of [M+Na]⁺ ions, the relative contents of cyclic and linear oligoesters were evaluated. Full article

In this study, various diamine monomers were used to synthesize aramid polymer films via a low-temperature solution condensation reaction with diacid chloride. For diamines with relatively high basicity, the reaction system became opaque because amine salt formation inhibited polymer synthesis. Meanwhile, low-basicity diamines with strong electron-withdrawing groups, such as CF₃ and sulfone, were smoothly polymerized without amine salt formation to provide highly viscous solutions. The acid byproduct HCl generated during polymerization was removed by adding propylene oxide to the reaction vessel and converting the acid into highly volatile inert substances. The resulting solutions were used as varnishes without any additional purification, and polymer films with an excellent appearance were easily obtained through a conventional casting and convection drying process. The films neither tore nor broke when pulled or bent by hand; furthermore, even when heated up to 400 °C, they did not decompose or melt. Moreover, polymers prepared from 2,2-bis(trifluoromethyl)benzidine (TFMB) and bis(4-aminophenyl)sulfone (pAPS) did not exhibit glass transition until decomposition. The prepared polymer films showed a high elastic modulus of more than 4.1 GPa and a high tensile strength of more than 52 MPa. In particular, TFMB-, pAPS-, and 2,2-bis(4-aminophenyl)hexafluoropropane-based polymer films were colorless and transparent, with very high light transmittances of 95%, 96%, and 91%, respectively, at 420 nm and low yellow indexes of 2.4, 1.9, and 4.3, respectively. Full article

Epoxy resins find extensive utility across diverse applications owing to their exceptional adhesion capabilities and robust mechanical and thermal characteristics. However, the demanding reaction conditions, including extended reaction times and elevated reaction temperature requirements, pose significant challenges when using epoxy resins, particularly in advanced applications seeking superior material properties. To surmount these limitations, the conventional approach involves incorporating organic catalysts. Within the ambit of this investigation, we explored the catalytic potential of metallic powders, specifically bismuth (Bi) and silver (Ag), in epoxy resins laden with various curing agents, such as diacids, anhydrides, and amines. Metallic powders exhibited efficacious catalytic activity in epoxy–diacid and epoxy–anhydride systems. In contrast, their influence on epoxy–amine systems was rendered negligible, attributed to the absence of requisite carboxylate functional groups. Additionally, the catalytic performance of Bi and Ag are different, with Bi displaying superior efficiency owing to the presence of inherent metal oxide layers on its powder surfaces. Remarkably, the thermal and mechanical properties of uncatalyzed, fully cured epoxy resins closely paralleled those of their catalyzed counterparts. These findings accentuate the potential of Bi and Ag metal catalysts, particularly in epoxy–diacid and epoxy–anhydride systems, spanning a spectrum of epoxy-based applications. In summary, this investigation elucidates the catalytic capabilities of Bi and Ag metal powders, underscoring their ability to enhance the curing rate of epoxy resin systems involving diacids and anhydrides but not amines. This research points toward a promising trajectory for multifarious epoxy-related applications. Full article

Films of a vitrimer based on the reaction between diglycidylether of bisphenol A and glutaric acid in the presence of 1-methylimidazole were processed using a solvent-based technique. The curing schedule was divided into two steps: first, a soluble linear polymer was formed through the reaction of the diacid and the diepoxide, and then the crosslinking was induced at a higher temperature via transesterification reactions. This epoxy–acid vitrimer was modified with multi-walled carbon nanotubes (MWCNTs) functionalized with β-hydroxyesters, produced by a robust and straightforward strategy based on a two-phase reaction between oxidized MWCNTs and phenylglycidylether. Nanocomposite vitrimer films were obtained by drop casting a dispersion of the functionalized MWCNTs in the linear polymer/cyclohexanone solution, followed by a thermal treatment. A high degree of dispersion of the carbon nanostructures was attained thanks to the β-hydroxyester functionalization when compared with oxidized MWCNTs. Nanocomposite films showed a significant photothermal effect (reaching 200 °C or above in 30 s) upon NIR light irradiation (850 nm) from a single LED (500 mW/cm²). The released heat was used to activate the shape memory effect and weld and heal the vitrimer matrix, proving the success of this easy strategy for the generation of remotely activated carbon-based vitrimer nanocomposites. Full article

The highly distorted water-soluble 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (Br₈TPPS₄⁴⁻) is readily protonated under acidic pH, forming the diacid H₂Br₈TPPS₄²⁻ and subsequently the zwitterionic H₄Br₈TPPS₄, which eventually evolves into J-aggregates. These latter species exhibit a relevant bathochromic shift with respect to the monomer with a quite sharp band due to motional narrowing. The depolarization ratio measured in resonant light scattering spectra allows estimating a tilt angle of ~20° of the porphyrins in the J-aggregate. The kinetic parameters are obtained by applying a model based on the initial slow nucleation step, leading to a nucleus containing m monomers, followed by fast autocatalytic growth. The k_c values for this latter step increase on decreasing the acid concentration and on increasing the porphyrin concentration, with a strong power-law dependence. No spontaneous symmetry breaking or transfer of chirality from chiral inducers is observed. Both Atomic Force Microscopy (AFM) and Dynamic Light Scattering (DLS) point to the presence, in both the solid and solution phases, of globular-shaped aggregates with sizes close to 130 nm. Density functional theory (DFT) calculations performed on simplified models show that (i) upon protonation, the saddled conformation of the porphyrin ring is slightly altered, and a further rotation of the aryl rings occurs, and (ii) the diacid species is more stable than the parent unprotonated porphyrin. Time-dependent DFT analysis allows comparing the UV/Vis spectra for the two species, showing a consistent red shift upon protonation, even if larger than the experimental one. The simulated Raman spectrum agrees with the experimental spectrum acquired on solid samples. Full article

While there is abundant literature on using a wide range of biomaterials to make polymers for various adhesive applications, most researchers have generally overlooked developing new adhesives from commercially available bio-based dimerized fatty acids. Some of the literature on the chemistry taking place during the clay-catalyzed dimerization of unsaturated fatty acids is generally misleading in that the mechanisms are not consistent with the structures of these dimers and a by-product isostearic acid. A selective acid-catalyzed interlayer model is much more logical than the widely accepted model of clay-catalyzed Diels–Alder reactions. The resulting dimers have a variety of linkages limiting large crystal formation either as oligomeric amides or polyamides. These highly aliphatic fatty acid dimers are used to make a wide range of hot melt polyamide adhesives. The specific structures and amounts of the diacids and diamines and their relative ratios have a big effect on the bio-based polyamide mechanical properties, but analysis of the structure–property relationships has seldom been attempted, since the data are mainly in the patent literature. The diacids derived from plant oils are valuable for making polyamides because of their very high bio-based content and highly tunable properties. Full article

This paper focuses on the implementation of a constrained Dynamic Matrix Control (DMC) approach within the level processes of the FESTO™ MPS-PA Compact Workstation plant in the context of the Industrial Internet of Things (IIoT) paradigm. The goal is to develop an industrial control application with decentralized logic that optimizes the operation of the plant while adhering to specific constraints. The implementation is carried out using the IEC-61499 standard and the OPC-UA protocol, enabling seamless communication between devices and systems. The authors utilize the 4diac-IDE and 4diac-FORTE as the development and runtime environments, respectively, to enable the execution of the control application on low-cost devices. The Beagle Bone Black (BBB) card is used for data acquisition and actuator control. Three types of constraints are considered: control increment ($\Delta u\left(k\right)$), output ($ym\left(k\right)$), and control ($u\left(k\right)$) constraints, to prevent unnecessary stress on the actuator and avoid damage to the plant. The QP algorithm is employed to optimize the objective function and address these constraints effectively. By integrating advanced control strategies into industrial processes in the IIoT paradigm and implementing them on low-cost devices, this paper demonstrates the feasibility and effectiveness of improving system performance, resource utilization, and overall productivity while considering system limitations and constraints. Full article