Polymer Films Research Articles

Controlling the Thermoelectric Performance of Doped Naphthobisthiadiazole-Based Donor-Acceptor Conjugated Polymers through Backbone Engineering.

This study investigates backbone engineering and evaluates the thermoelectric properties of FeCl3-doped naphthobisthiadiazole (NTz)-based donor-acceptor (D-A) conjugated polymer films. The NTz acceptor unit is coupled with three distinct donor units, namely dialkylated terthiophene (3T), dialkylated quaterthiophene (4T), and dialkylated bisthienyl thienothiophene (2T-TT) to yield copolymers designated as PNTz3T, PNTz4T, and PNTzTT. The difference in donor units leads to diverse molecule stacking and electronic properties, which can be systematically discovered via the three polymers. The linear structure of PNTz4T enables an orderly arrangement of side chains, thereby promoting dopant intercalation for enhanced carrier concentration. Additionally, this linear structure leads to an edge-on stacking mode, thereby improving the in-plane carrier mobility. As a result, the doped PNTz4T exhibits the highest electrical conductivity (σ) of 88.3 S cm-1 along with a Seebeck coefficient (S) of 62.2 µV K-1, thereby achieving the highest power factor (PF) of 34.2 µW m-1 K-2. These results highlight the relationship between the molecular design, microstructure, and doping effects in manipulating the thermoelectric performance of doped NTz-based D-A polymers.

The Impact of π-Bridge Moiety on the Optoelectronic Properties and Photochemical Stabilities of Benzodithiophene-Based Conjugated Polymers

The stability of conjugated polymers (CPs) under exposure to light and air determines their sustainability for commercial use and their possible usage in diverse areas. The main goal of this study is to examine how changes in the π-bridge of polymers affect their electrochemical and optoelectronic properties. Furthermore, it seeks to evaluate the impact of these alterations on the photochemical durability of the polymers. Three D-π-A types of CPs were synthesized via Stille coupling. All polymers consist of the same acceptor and donor units, which were benzooxadiazole (BOz) and benzo[1,2-b:4,5-b']dithiophene (BDT), respectively, but they had different π-bridge such as thiophene (T), selenophene (Se), and thiazole (Tz).This study used a variety of spectroscopic tools such as UV-Vis, FTIR, and XPS, to investigate how photooxidation occurs. DFT calculations were used to further support the experimental results. Within a mere 30-minute timeframe, the primary absorption peak of the polymer films experienced a blue shift and a significant reduction in intensity due to being exposed to both light and air simultaneously. Despite the presence of the same electron-withdrawing group, BOz, and electron-donating group, BDT, in all polymers, the photochemical stability varies with π-bridges. T- and Se-containing conjugated polymer films (P1-T, P2-Se) exhibited a significant decrease in the intensity of their peak absorption, whereas the peak intensity and characteristics of their thiazole counterpart (P3-Tz) only showed a slight alteration after being exposed to light and air for up to 7 hours. The superior photostability of the P3-Tz polymer film can be attributed to a significantly higher HOMO level and higher band gap in comparison to P1-T and P2-Se.Comprehending the photochemical stability of these polymers is crucial for progressing their commercial uses, such as organic photovoltaics, OLEDs, and sensors. This study highlights the significance of choosing suitable π-bridges to improve the longevity and effectiveness of CPs, thus satisfying market requirements and broadening their possible applications.

Damping and acoustic properties of nanosilica filled poly(styrene-acrylate) interpenetrating polymer networks (IPNs): Effect of nanocomposite preparation method

Research on noise pollution reduction has focused on utilizing damping coatings and polymer nanocomposites to enhance sound absorption. Nanosilica/poly(styrene-acrylate) nanocomposites as a water-based coating were prepared through in-situ emulsion polymerization and direct mixing methods at varying concentrations of 1, 2, and 3 wt% of nanosilica. Fourier transform infrared (FTIR) spectroscopy revealed that the inclusion of surfactant-containing micelles and a more extended synthesis period in the in-situ synthesis technique enhanced the interaction between silica nanoparticles and polymer chains. Dynamic light scattering (DLS) analysis showed a unimodal distribution and an acceptable range of polydispersity index (PDI) for neat and nanocomposite latexes. The addition of silica nanoparticles enhanced the stability of latex particles, especially evident in the direct mixing method. The field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images confirmed the better dispersion of nanoparticles within the polymer matrix in the in-situ method. The addition of nanosilica resulted in a significant increase in pseudoplastic behavior and viscosity, notably in the in-situ synthesis. In both the in-situ synthesis and direct mixing techniques, the addition of 1 wt% of nanosilica resulted in an increase in the damping factor of nanocomposite films to about 2. However, when the nanosilica content was further increased to 3 wt%, the damping factor decreased. Acoustic tests demonstrated improved sound absorption with silica nanoparticles, yielding noise reduction coefficient (NRC) values of 0.49 and 0.46 for in-situ synthesis and direct mixing. The direct mixing method notably enhanced tensile properties at all nanoparticle content levels. Dried nanocomposite films exhibited superior UV-blocking capabilities compared to neat polymer films.

A self-regenerative heat pump based on a dual-functional relaxor ferroelectric polymer.

Electrocaloric (EC) cooling presents a promising approach to efficient and compact solid-state heat pumps. However, reported EC coolers have complex architectures and limited cooling temperature lift. In this work, we introduce a self-regenerative heat pump (SRHP) using a cascade of EC polymer film stacks, which have electrostrictive actuations in response to an electric field that are directed to realize efficient heat transfer, eliminating the need for additional transportive or regenerative mechanisms. The SRHP demonstrates a cooling of 8.8 kelvin below ambient temperature in 30 seconds and delivers a maximum specific cooling power of 1.52 watts per gram. The temperature lift of the SRHP is 14.2 kelvin. These results underscore the potential of the compact solid-state cooling mechanism to address the increasing need for localized thermal management.

Structural, optical, and shielding investigation of PVA/Te composite for technological applications

Using the casting process, polymeric films made of polyvinyl alcohol (PVA) including varying percentages of Te were created to form PVA/Te composite at doping concentrations of Te (0, 4.76, 13.04, 20 wt %), which denoted as PT1, PT2, PT3 and PT4 respectively. XRD results show semicrystalline nature in PT1 and PT2 however with further increasing of Te contents, a nano-crystallite Te appeared in PT3 and PT4. The absorption spectrum confirms that PT3 film is a good option to be used in UV-shielding. PT4 film shows an abrupt rise in absorption coefficient at 0.5 eV, 1.5 eV and UV regions, hence this qualifies this sample for various optical applications. The optical energy gap of the films varies between 4.94 eV and 3.32 eV for the indirect transitions and between 5.3 eV and 4.5 eV for the direct transitions, the PT4 film has the lowest values of both direct and indirect energy gaps. Several methods were used to measure the average refractive index nav value. Furthermore, the nonlinear refractive index (n2) was estimated. PT4 possesses the highest value of both nav and n2. Furthermore, the radiation shielding coefficients have been estimated according to the Phy-X/PSD online software. The sample with the highest Te concentration, PT4, has the best radiation shielding between the films under investigation. The investigated polymer with high Te weight percentage is an optical system that can be used for solar cells, optoelectronics, electronics, nonlinear optics, optical filters and for radiation shielding.

The Properties of Thin Films Based on Chitosan/Konjac Glucomannan Blends

In this work, blend films were prepared by blending 2% chitosan (CS) and 0.5% konjac glucomannan (KGM) solutions. Five ratios of the blend mixture were implemented (95:5, 80:20, 50:50, 20:80, and 5:95), and a pure CS film and a pure KGM film were also obtained. All the polymeric films were evaluated using FTIR spectroscopy, mechanical testing, SEM and AFM imaging, thermogravimetric analyses, swelling and degradation analyses, and contact angle measurements. The CS/KGM blends were assessed for their miscibility. Additionally, the blend films’ properties were evaluated after six months of storage. The proposed blends had good miscibility in a full range of composition proportions. The blend samples, compared to the pure CS film, indicated better structural integrity. The surface structure of the blend films was rather uniform and smooth. The sample CS/KGM 20:80 had the highest roughness value (Rq = 12.60 nm). The KGM addition increased the thermal stability of films. The blend sample CS/KGM 5:95 exhibited the greatest swelling ability, reaching a swelling degree of 946% in the first fifteen minutes of the analysis. Furthermore, the addition of KGM to CS improved the wettability of the film samples. As a result of their good mechanical properties, surface characteristics, and miscibility, the proposed CS/KGM blends are promising materials for topical biomedical and cosmetic applications.

High Performance and Colorful Polymer Thermoelectrics with Imprinted Porous Film.

The rapid development of the Internet of Things and wearable electronics has generated growing interest in creating high-performance and visually striking polymer thermoelectric (TE) devices. However, existing polymer TE materials have yet to fully meet these diverse demands. In this study, imprinted porous polymer films are introduced that exhibit both high TE performance and a spectrum of structural colors. The porous architecture not only preserves excellent charge transport properties but also significantly enhances phonon-like scattering, resulting in a more than 50% reduction in thermal conductivity for the PDPPSe-12 film. This leads to a 170% increase in the figure of merit (ZT), achieving a peak value of 0.52 at 363K. Furthermore, the highly ordered porous structure imparts the PDPPSe-12 films with both a wide range of structural colors and remarkable stretchability, making them ideal for wearable TE generators. This approach is widely applicable to various polymeric systems, offering a novel strategy for advancing state-of-the-art plastic TE materials through microstructural engineering.

Deformation Behavior of Microparticle-Based Polymer Films Visualized by AFM Equipped with a Stretching Device.

Understanding the structural changes and property alterations at the nanoscale and microscopic levels is critical to clarifying the deformation behavior and mechanical properties of polymer materials. Especially, in latex films composed of polymer nanoparticles, it is widely accepted that the remaining interfaces between microparticles in the film affect their brittleness. However, detailed information on nanoscale changes of latex films during deformation remains unclear due to technical difficulties in analyzing the microstructures under mechanical stress. In this study, we employed atomic force microscopy equipped with a uniaxial stretching device to visualize the surface structures of films composed of slightly cross-linked microparticles under elongation strain. The observations revealed that the latex film deforms in a nonaffine manner, which is attributed to the concurrent deformation of individual microparticles and the pull-out of interpenetration between them. Furthermore, by introducing a load-strain measurement mechanism to the stretching device, we compared the relationships between nanostructural changes, local property changes, and macroscopic deformation of microparticle-based films. The results suggest that loads are dominated by the deformation of microparticles and dissipate as the interpenetration of surface polymer chains between microparticles is pulled out.

Engineering and modification of physical properties of thermoplastic polymeric films using oxygen ions bombardment for industrial applications

Engineering and modification of physical properties of thermoplastic polymeric films using oxygen ions bombardment for industrial applications

Low-cost, high-volume, manufacturable 0.88 NA multi-wavelength diffractive lens array for optical document security

We design, manufacture, and characterize a high-numerical-aperture (NA=0.88, f/0.27), multi-wavelength (480 nm, 550 nm, and 650 nm) multilevel diffractive microlens array (MLA). This MLA achieves multi-wavelength focusing with a depth of focus (DoF) twice the diffraction-limited value. Each microlens in the array is closely packed with a diameter of 70 µm and a focal length of 19 µm in air. The MLA is patterned on one surface of a polymer film via UV casting, positioning the focal plane at the distal end of the polymer film. Each microlens focuses light at three design wavelengths into a focal spot with an estimated FWHM of ∼310nm. By placing this MLA directly on a standard high-resolution banknote print (minimum feature width of 10–15 µm), we demonstrate color-integral imaging for anti-counterfeiting. In contrast, refractive MLAs cannot achieve high-NA, multi-wavelength focusing or extended DoF. The extended DoF of our MLA ensures reliable performance despite variations in the polymer film’s thickness. Our MLA, produced via UV casting, enables extremely low-cost, high-volume production, making it ideal for flat optics in banknotes and document security.

In situ Cyclization of Aromatic Thioethers in Emissive Materials to Generate Phosphorescent Dibenzothiophenes

AbstractIn this contribution, we explored the photocyclization of thioethers to highly substituted dibenzothiophenes (DBT) using solely UV‐light without any need for additives. This cost‐effective, robust and environmentally friendly approach yielded phosphorescent compounds, which were characterized by X‐ray crystallography and state‐of‐the‐art photophysical methods. The resulting DBTs feature ultralong photoluminescence lifetimes and quantum yields close to unity in frozen glassy matrices. The reaction mechanism was elucidated in detail through a combination of quantum chemical calculations and experimental results, providing evidence that triplet states are involved in the cyclization process. Additionally, the photoreaction can also be induced within materials. For this purpose, the precursors were integrated into polymer films or polymer resins suitable for 3D printing. Irradiation of these polymeric objects allows motifs with ultralong phosphorescence to be irreversibly inscribed through the proceeding photocyclization. The in situ photogeneration of DBTs from aromatic thioethers overcomes the observed incompatibilities regarding solubility in polymer resins for 3D printing.

Scalable all polymer dielectrics with self-assembled nanoscale multiboundary exhibiting superior high temperature capacitive performance

Polymers are key dielectric materials for energy storage capacitors in advanced electronics and electric power systems due to their high breakdown strengths, low loss, great reliability, lightweight, and low cost. However, their electric and dielectric performance deteriorates at elevated temperatures, making them unable to meet the rising demand for harsh-environment electronics such as electric vehicles, renewable energy, and electrified transportation. Here, we present an all-polymer nanostructured dielectric material that achieves a discharged energy density of 7.1 J/cm³ with a charge-discharge efficiency of 90% at 150°C, outperforming the existing dielectric polymers and representing more than a twofold improvement in discharged energy density compared with polyetherimide. The self-assembled nano-scale multiboundaries effectively impede the charge injection and excitation, leading to more than one order of magnitude lower leakage current density than the pristine polymer matrix PEI at high electric fields and elevated temperature. In addition, the film processing is simple, straightforward, and low cost, thus this all-polymer nanostructured dielectric material strategy is suitable for the mass production of dielectric polymer films for high-temperature capacitive energy storage.

Intrinsically Antibacterial Carbon Nanoparticles Optimally Entangle into Polymeric Films to Produce Composite Packaging

Intrinsically Antibacterial Carbon Nanoparticles Optimally Entangle into Polymeric Films to Produce Composite Packaging

Characterization of Plasma Jet Treated Composite Chitosan with Hydroxyapatite Nanoparticles Films

ABSTRACT The paper investigates the properties of polymer composite films comprised of chitosan and 1% hydroxyapatite nanoparticles following treatment with a plasma jet, using argon as the working gas. Hydroxyapatite is typically added to chitosan to enhance its mechanical properties. The study found that plasma jet treatment increases both the mechanical strength and elastic modulus of the films. Additionally, the treatment reduces the water contact angle (WCA) from 70° to 26°, indicating improved hydrophilicity от. FTIR spectroscopy results confirm that no new chemical bonds are formed during the treatment. Scanning electron microscopy (SEM) images reveal the removal of amorphous regions in the polymer film post-treatment. This modification enhances the adhesion of human fetal mesenchymal stem cells (FetMSCs) to the film, suggesting that these treated films could be suitable for biomedical applications.

A Polymer Film with Very High Seebeck Coefficient and Overall Thermoelectric Properties by Secondary Doping, Dedoping Engineering and Ionic Energy Filtering

AbstractThermoelectric (TE) materials are significant for sustainable development because they can be used to harvest waste heat into electricity. Organic TE materials have unique merits including high mechanical flexibility, low cost, and low intrinsic thermal conductivity. But their TE properties particularly the Seebeck coefficient are notably lower than the inorganic counterparts. Here, a poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) film is reported with a very high Seebeck coefficient and figure of merit (zT) at room temperature through secondary doping, dedoping engineering, and ionic energy filtering. The PEDOT:PSS films are successively treated with acid, base, and vitamin C that is a reductant, and then coated with 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIM:DCA) that is an ionic liquid. This can exhibit a record‐high Seebeck coefficient and power factor of 111 µV K−1 and 1285 µW m−1 K−2, respectively, and the corresponding zT value is 1.05. This is the highest zT value for polymers and polymer composites, and it is comparable to that of the best inorganic TE materials.

Strain-dependent charge trapping and its impact on the operational stability of polymer field-effect transistors

Despite recent dramatic improvements in the electronic characteristics of stretchable organic field-effect transistors (FETs), their low operational stability remains a bottleneck for their use in practical applications. Here, the operational stability, especially the bias-stress stability, of semiconducting polymer-based FETs under various tensile strains is investigated. Analyses on the structure of stretched semiconducting polymer films and spectroscopic quantification of trapped charges within them reveal the major cause of the strain-dependent bias-stress instability of the FETs. Devices with larger strains exhibit lower stability than those with smaller strains because of the increased water content, which is accompanied by the formation of cracks and nanoscale cavities in the semiconducting polymer film as results of the applied strain. The strain-dependence of bias-stress stability of stretchable OFETs can be eliminated by passivating the devices to avoid penetration of water molecules. This work provides new insights for the development of bias-stable stretchable OFETs.

Wetting-Induced Elastocapillary Deformation of Supported Thin Rubbery Polymer Films

Wetting-Induced Elastocapillary Deformation of Supported Thin Rubbery Polymer Films

Multidimensional analysis of textiles coated with electroactive polymers for actuators

This paper presents a multidimensional analysis of textiles coated with conductive polymers for actuators. The purpose of using multidimensional scaling analysis is to compare similarities and dissimilarities between conductive textiles obtained through conductive polymeric film deposition to observe the optimal value for electrical resistance and to select an adequate method to achieve conductive fabric using different polymers (polyethylene glycol, polyvinyl alcohol or polyvinylidene fluoride) and metal microparticles (copper or nickel). The multidimensional analysis is based on mapping a series of material properties from a proximity matrix (similarities or dissimilarities) between these properties. Multidimensional scaling allows rebuilding the exact map of the values (within approximately a symmetry or rotation). To fit dissimilarity or similarity matrices for multiple variables into one common space estimating the weight parameters for each variable, the INDSCAL model (individual differences multidimensional scaling) was used.

Mode-locked soliton pulse generation using copper phthalocyanine absorber in long erbium-doped fibre laser cavity

We present the development of a mode-locked erbium-doped fibre laser (EDFL) utilizing Copper Phthalocyanine (CuPc) as a saturable absorber (SA). CuPc exhibits unique optical properties, including its high nonlinear optical response and rapid recovery time. To seamlessly integrate CuPc into the laser cavity, we employed a simple embedding technique within a polymer film. The SA demonstrates a modulation depth of 3.1% and a saturation intensity of 17 MW/cm2. Operating within a pump power range of 90.6 to 122.9 mW, the laser achieves mode-locked operation, producing a soliton pulse train with a fundamental frequency of 1.82 MHz and a pulse width of 6.4 ps at a wavelength of 1561.5 nm. It attains a maximum output power of 13.97 mW and a pulse energy of 7.67 nJ. These results underscore CuPc's potential as a promising material for generating mode-locked pulses, suggesting new avenues in ultrafast laser development for diverse applications.

Ultrafast laser-induced simultaneous carbonization and texturization of titanium alloy surface and its tribological properties

Due to the poor tribological properties, the applications of titanium alloy are restricted. Both laser texturing and surface coating are effective methods to enhance the tribological properties of titanium alloy surfaces. Hence, this study proposed a new ultrafast laser-induced simultaneous carbonization and texturization of titanium alloy surfaces to improve its tribological properties by modifying titanium alloy’s surface composition and micro-nanostructures in one step. A polymer film (polyimide, PI) was selected as the carbon source preplaced on the titanium alloy (Ti-6Al-4 V, TC4) surface. On the one hand, under ultrafast laser (picosecond 355 nm laser) irradiation, the laser-induced photothermal effect led to the carbonization of the polymer film and the formation of the pyrolytic carbon coating on the titanium alloy surface. Pyrolytic carbon also reacted with titanium alloy to form titanium carbides. On the other hand, ultrafast lasers also led to the melting and ablation of the titanium alloy surface, creating micro-nanostructures with interlocking micro-holes and micro-bumps. The coefficient of friction (COF) and wear rate of the titanium alloy surfaces were significantly reduced due to the synergistic effects of carbon coating and micro-nanostructures. It showed great significance in improving the tribological properties and the surface treatment of metallic materials.