Alignment Of Polymer Chains Research Articles

Anisotropic Poly(vinylidene fluoride-co-trifluoroethylene)/MXene Aerogel-Based Piezoelectric Nanogenerator for Efficient Kinetic Energy Harvesting and Self-Powered Force Sensing Applications.

Lightweight flexible piezoelectric devices have garnered significant interest over the past few decades due to their applications as energy harvesters and wearable sensors. Among different piezoelectrically active polymers, poly(vinylidene fluoride) and its copolymers have attracted considerable attention for energy conversion due to their high flexibility, thermal stability, and biocompatibility. However, the orientation of polymer chains for self-poling under mild conditions is still a challenging task. Herein, anisotropic poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE)/MXene aerogel-based piezoelectric generators with highly oriented MXene fillers are fabricated. The unidirectional freezing of a hybrid solution facilitates the strain-induced alignment of MXene nanosheets and polymer chains along the solvent crystal growth direction due to the robust interactions between the MXene nanosheets (O-H/F groups) and PVDF-TrFE chains (F-C/C-H groups). Consequently, this process fosters the development of abundant electroactive β crystals with preferred alignment characteristics, leading to the formation of intrinsic self-oriented dipoles within the PVDF-TrFE aerogel. As a result, the piezoelectric properties of PVDF-TrFE are fully harnessed without any complex poling process, resulting in an open-circuit voltage of around 40 V with MXene loading of 3 wt % in anisotropic aerogel, which is 2-fold higher than that of the corresponding isotropic aerogel where the MXene nanosheets and polymer chains are randomly aligned. Furthermore, the developed piezoelectric nanogenerator was demonstrated as a tactile sensor which showed a high sensitivity of 9.6 V/N for lower forces (less than 2 N) and a sensitivity of 1.3 V/N in the higher force regime (2 N < force < 10 N). The strategy adopted here not only provides the enhancement of the piezoelectric crystalline form for self-poling but also paves an avenue toward developing self-powered energy harvesters using piezoelectric polymers.

Water-responsive Contraction for Shape-adaptive Bioelectronics

Water-responsive adaptive contraction represents a pivotal advancement in bioelectronics, offering unparalleled advantages over traditional swollen hydrogels and actuator-based systems. This review explores mechanisms including phase transition, hydrogen bond disruption, and hierarchical hybridization to enable rapid and substantial shape adaptability upon moisture exposure without external control and highlights various component modulation and porous and heterostructure engineering strategies to provide directional control and multifunctionality. Additionally, recent advances in supercontractile films, achieved through cold-drawing processes that disrupt hydrogen bonds in aligned polymer chains are overviewed for wearable and implantable biomedical applications where seamless tissue interfacing is essential. These advances address long-standing challenges in device integration with biological tissues, such as rigidity and inflammation, by creating electrodes that naturally conform to tissue shapes. This review delves into water-responsive adaptive contraction in bioelectronics, emphasizing its potential to revolutionize medical implants, wearable health monitors, and soft robotics by naturally conforming to tissue shapes upon moisture exposure. They promise significant improvements in chronic electronic integration and patient care, paving the way for next-generation medical devices, soft robotics, and smart textiles that adapt dynamically to biological environments.

Bulk thermally conductive polyethylene as a thermal interface material.

As the demand for high-power-density microelectronics rises, overheating becomes the bottleneck that limits device performance. In particular, the heterogeneous integration architecture can magnify the importance of heat dissipation and necessitate electrical insulation between critical junctions to prevent dielectric breakdown. Consequently, there is an urgent need for thermal interface materials (TIMs) with high thermal conductivity and electrical insulation to address this challenge. In this work, we synthesized thermally conductive polyethylene (PE) bars with vertically aligned polymer chains via a solid-state drawing technique to achieve a thermal conductivity of 13.5 W m-1 K-1 with a coverage area of 2.16 mm2. We utilized wide-angle X-ray scattering to elucidate the molecular structural changes that led to this thermal conductivity enhancement. Furthermore, we conducted a device-cooling experiment and showed a 39% hot spot temperature reduction compared to a commercial ceramic-filled silicone thermal pad under a heating power of 3.6 W. Thus, this bulk-scale thermally conductive PE bar with nanoscale structural refinement demonstrated superior cooling performance, offering potential as an advanced thermal interface material for thermal management in microelectronics.

Impact of Dilute DIO Additive on Local Microstructure of Fluorinated, pNDI-Based Polymer Solar Cells.

The performance of all-polymer solar cells is often enhanced by incorporating solvent additives during solution processing. In particular, blends based on the model all-polymer system PBDBT:N2200 have been shown to have increased short-circuit current and fill factor when processed with dilute diiodooctane (DIO). However, the morphological mechanism that drives the increase in performance is often not well understood due to limitations in common characterization techniques. In this study, it is shown that a combination of X-ray techniques with cryogenic high-resolution transmission electron microscopy (HRTEM) analysis can provide a quantitative and spatially resolved picture of polymer chain orientation and alignment in all-polymer blends. It is found that DIO induces vertical phase separation in PBDBT-2F:F-N2200 and increases donor crystallite thickness in the pi-stacking direction leading to an acceptor-rich film surface. However, it is also shown that DIO does not disrupt the formation of face-on donor-acceptor interfaces. These findings suggest that dilute DIO primarily affects crystalline domain formation in single component regions as opposed to mixed regions; thus, dilute DIO can impact vertical charge transport pathways without sacrificing donor-acceptor interfacial connectivity.

Effect of macromolecular structure modification of kapok fibers by silane treatment on mechanical properties of their reinforced composites

AbstractThe present study investigates the usability of lignocellulosic kapok fibers as a reinforcement for lightweight composites. Kapok fibers are modified by dewaxing followed by a silane coupling agent at different concentrations. The crystallographic structure and the alignment of silane linkage polymer chains on fiber structure are examined using X‐ray Diffraction (XRD). The linkage of chemical bonds (SiOC And SiOSi) between the polymer structure of the fiber and silane coupling agent is confirmed from FTIR spectroscopy. Additionally, the small angle X‐ray scattering (SAXS) study is done considering kapok fiber as a nonideal two‐phase system and the study investigates the modification occurring within the macromolecular structure of the kapok fiber. Following the grafting of silanes onto the fiber, silane‐modified kapok fiber‐reinforced epoxy composites are fabricated using the hand lay‐up technique. The chemical treatments on the fiber, enhanced flexural, tensile and impact strength of the composites by 132%, 102%, and 146% respectively.

Development of Multi-Walled Carbon Nanotube-Integrated Recycled Polyethylene Terephthalate Electrospun Antibacterial Face Mask

In this study, electrospun nanofiber membranes were successfully fabricated by modifying recycled polyethylene terephthalate (r-PET) with multi-walled carbon nanotubes (MWCNTs) for face mask applications. The recycling of PET bottles ensures effective waste management, while the electrospinning process facilitates the creation of delicate nano-range fibers. The inclusion of MWCNTs aimed to assess the antibacterial activity of the resulting nanomembranes. The fabricated samples underwent comprehensive characterization, including scanning electron microscopy (SEM), ultimate tensile testing, particulate filtration efficiency (PFE) testing, Fourier transform infrared spectroscopy (FTIR), and antibacterial sensitivity assays, revealing significant findings. MWCNTs incorporation led to minor bead formation in the membranes, with fiber diameters ranging from 446 to 862 nm. However, MWCNTs resulted in reduced stiffness and tensile properties due to the disruption of polymer chain alignment. The nanofiber membranes demonstrated effective filtration of 0.3 µm particulates, achieving filtration rates between 96 to 97%Functional group analysis confirmed the presence of both r-PET and MWCNTs in the composites. Although the r-PET/MWCNTs 12 kV membrane lacked an antibacterial zone of inhibition, it exhibited reductions of 28.64% for S. aureus and 31.9% for E. coli. These results collectively underscore the potential of r-PET/MWCNTs samples as an alternative nanofibrous membrane material for face masks. J. of Sci. and Tech. Res. 5(1): 63-74, 2023

High Thermal Conductive Liquid Crystal Elastomer Nanofibers.

Liquid crystal elastomers (LCEs), consisting of polymer networks and liquid crystal mesogens, show a reversible phase change under thermal stimuli. However, the kinetic performance is limited by the inherently low thermal conductivity of the polymers. Transforming amorphous bulk into a fiber enhances thermal conductivity through the alignment of polymer chains. Challenges are present due to their rigid networks, while cross-links are crucial for deformation. Here, we employ hydrodynamic alignment to orient the LCE domains assisted by controlled in situ cross-linking and to remarkably reduce the diameter to submicrons. We report that the intrinsic thermal conductivity of LCE fibers at room temperature reaches 1.44 ± 0.32 W/m-K with the sub-100 nm diameter close to the upper limit determined in the quasi-1D regime. Combining the outstanding thermal conductivity and thin diameters, we anticipate these fibers to exhibit a rapid response and high force output in thermomechanical systems. The fabrication method is expected to apply to other cross-linked polymers.

Improvement in dielectric properties of polyacrylate copolymers by engineering the interphase region with polymer-grafted reduced graphene oxide

In this study, an innovative interfacial design strategy aimed to investigate the effects of interfacial interactions between the matrix and reduced graphene oxide (rGO) on the dielectric properties of nanocomposites. The polymer matrices with varying comonomer ratios of butyl acrylate and methyl methacrylate were synthesized to deliberately engineer diverse interfacial interactions with polymer-grafted reduced graphene oxide. Through this approach, fine-tuned interfacial interactions between the polymer matrix and polymer-grafted rGO were achieved, which was verified by FE-SEM, DSC, and DMTA analysis. Subsequently, the dielectric properties of the nanocomposites were investigated to elucidate the relationship between interfacial strength and dielectric efficiency. It was found that polymer nanocomposites with enhanced interfacial interactions exhibit higher dielectric permittivity compared to the neat matrix. This enhancement was attributed to the increased charge storage in the interfacial area and improved alignment of polarizable polymer chains in the interphase between the polymer matrix and polymer-grafted rGO.

Simultaneously enhancing the flow properties and mechanical strength of polyphenylene sulfide via in‐mold ultrasonic‐assisted injection molding

AbstractInjection molding is widely used for making intricate plastic products due to its precision, cost efficiency, and fast production. Industries like consumer electronics, aerospace, and medical, demand high mechanical properties from these parts. However, high‐performance polymers face challenges in flowability. Ultrasonic‐assisted injection molding offers a solution, but its impact on flowability and mechanical properties is not fully understood. We propose a novel injection mold design with in‐mold ultrasonic vibration to address this. By applying high‐frequency shear forces to the melt, it alters polymer chain alignment, enhancing flow and microstructure. Employing polyphenylene sulfide (PPS) resin as the primary material, this study systematically explores the impact of varying ultrasonic vibration durations and stages on melt filling behavior and product performance. Compared with conventional molds, ultrasonic‐assisted molds reduce melt viscosity by 38% and improve mechanical properties by 10.21%, with a 17.1% increase in crystallinity. This technology shows promise for improving flowability and mechanical properties in injection molding, with potential for wide industrial application.

Highly Stretchable and Oriented Wafer-Scale Semiconductor Films for Organic Phototransistor Arrays.

Stretchable organic phototransistor arrays have potential applications in artificial visual systems due to their capacity to perceive ultraweak light across a broad spectrum. Ensuring uniform mechanical and electrical performance of individual devices within these arrays requires semiconductor films with large-area scale, well-defined orientation, and stretchability. However, the progress of stretchable phototransistors is primarily impeded by their limited electrical properties and photodetection capabilities. Herein, wafer-scale and well-oriented semiconductor films were successfully prepared using a solution shearing process. The electrical properties and photodetection capabilities were optimized by improving the polymer chain alignment. Furthermore, a stretchable 10 × 10 transistor array with high device uniformity was fabricated, demonstrating excellent mechanical robustness and photosensitive imaging ability. These arrays based on highly stretchable and well-oriented wafer-scale semiconductor films have great application potential in the field of electronic eye and artificial visual systems.

Molecular Ball Joints: Mechanochemical Perturbation of Bullvalene Hardy-Cope Rearrangements in Polymer Networks.

The solution-state fluxional behavior of bullvalene has fascinated physical organic and supramolecular chemists alike. Little effort, however, has been put into investigating bullvalene applications in bulk, partially due to difficulties in characterizing such dynamic systems. To address this knowledge gap, we herein probe whether bullvalene Hardy-Cope rearrangements can be mechanically perturbed in bulk polymer networks. We use dynamic mechanical analysis to demonstrate that the activation barrier to the glass transition process is significantly elevated for bullvalene-containing materials relative to "static" control networks. Furthermore, bullvalene rearrangements can be mechanically perturbed at low temperatures in the glassy region; such behavior facilitates energy dissipation (i.e., increased hysteresis energy) and polymer chain alignment to stiffen the material (i.e., increased Young's modulus) under load. Computational simulations corroborate our work that showcases bullvalene as a reversible "low-force" covalent mechanophore in the modulation of viscoelastic behavior.

Studies on adsorptive dehydration of pasteurised milk by filled polymeric IPN hydrogel

ABSTRACT Adsorptive dehydration utilising polymeric hydrogels presents an effective technique for removing excess water from pasteurised milk. This study investigated three Interpenetrating Polymeric Network (IPN) hydrogels comprising Polyvinyl Alcohol (PVOH) and Hydroxyethyl Cellulose (HEC) at mass ratios of 90:10, 70:30 and 50:50, respectively, with Maleic Anhydride (MAn) as a cross-linker at concentrations of 2% 4%, and 8% based on total polymer weight. It was observed that the rate of dehydration increased with higher HEC content in the hydrogels. However, the stability decreased due to changes in the structural alignment of polymer chains and weak cross-linking. Among the tested hydrogels, the one with a composition of 70:30 for PVOH and HEC, respectively, cross-linked with 8% MAn (0.096gm), exhibited the best adsorption (569% Swelling) with minimal changes in pH (<10%) and conductivity (<10%) and was, therefore, selected for further study. This selected hydrogel composition was further enhanced by incorporating a hydrophilic nanofiller (Bentonite) at proportions of 2%, 4% and 6% based on total polymer weight during hydrogel synthesis. The hydrogel with 4% nanofiller (0.081 gm) showed the best results in terms of swelling and stability although the 6% filled hydrogel exhibited superior swelling but lower stability. Finally, the dehydration process was optimised using Type 1 fuzzy logic (T1FL), achieving an R2 value of 95.13%.

Dynamic Electrostatic Interfacial Engineering for Block Copolymer Microparticles with Reversible Structures.

Responsive nanoparticle surfactants (NPSs) can dynamically and reversibly modulate the interfacial interactions between incompatible components, which are essential in the interfacial catalysis, corrosion, and self-assembly of block copolymers (BCPs). However, NPSs with stimuli-responsive behavior often involve tedious chemical synthesis and surface modifications. Herein, we propose a strategy to in situ construct a kind of dynamic and reversible NPSs by the interfacial electrostatic interaction between the negatively charged nanoparticles (NPs) and the positively charged homopolymers. The NPSs assembled at the oil/water interface reduce the interfacial tension and direct the confined assembly of BCP. Meanwhile, the dynamic NPSs can be disassembled by increasing the pH value or introducing competitive electrostatic attractions, which can dynamically and reversibly change the interfacial properties as well as the alignment of polymer chains, enabling BCP microparticles with reversibly switchable lamellar and cylindrical structures. Furthermore, by the introduction of aggregation-induced emission luminogens as tails to the NPSs, the reversible transformation of BCP microparticles can be visualized by fluorescence emission, which is dependent on the nanostructures of microparticles. This work establishes a concept for dynamically manipulating interfacial interactions and reversibly switching BCP microparticles without time-consuming NPS synthesis, showing promising applications in the fabrication of smart materials with switchable structures and properties.

Long-range polymer ordering by directional coating to remarkably enhance the charge carrier mobility in PCDTPT-based organic field-effect transistors.

With the wide potential of organic field-effect transistors in all the modern electronic circuitries, researchers are grappling with the challenge of poor charge transport and hence lower mobility in organic polymers. Low-charge carrier mobility is mainly due to disorder in the molecular packing of organic semiconductors along with other factors, such as impurities, defects and interactions between molecules. The current research work has been conducted to align the molecular chains of poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-‌‌‌b:5,4-‌b']‌dithiophen-2-yl)-alt-[1,2,5]thiadiazolo-[3,4-c]pyridine] (PCDTPT) using directional coating techniques such as dip coating and brush coating on nano-grooved substrates. Long-range order of polymer chains was clearly observed along the direction of brush coating and nanogrooves in optical and atomic force microscope (AFM) images while transmission spectra confirmed decreased pi-pi stacking for the polymer films deposited by this technique. By comparing the mobility performance of brush-coated devices with other techniques, we found a remarkable mobility enhancement of 90 times that of conventional spin-coated device and 24 times enhancement compared with the dip-coated device for the case when the alignment of polymer chains was parallel to the channel. All the fabrication and characterizations were performed in the ambient environment. This study demonstrates a potential approach to align the polymers on long and short ranges hence providing a route for high-performing devices in ambient conditions.

Effect of layered transition metal dichalcogenide hybrid nanomaterials on the piezoelectric performance of non‐solvent induced phase separated polyvinylidene fluoride

AbstractLayered transition metal dichalcogenides (TMDs) with high aspect ratios enhance the alignment of polymer chains and induce a preferred orientation of the polymeric crystallites when incorporated into polyvinylidene fluoride (PVDF). In addition to offering an effective charge‐transfer mechanism, TMDs give PVDF more rigidity and piezoelectric qualities. This work reports the non‐solvent induced phase separation (NIPS) introduced while developing the PVDF/MoS2 composites. During the NIPS, the PVDF chains become phase‐separated, which induces high polarization in the PVDF matrix. Phase‐separated PVDF/MoS2 composites show high porosity and charge distribution attributed to the enhanced piezoelectric output voltage. While the neat PVDF demonstrated very feeble output voltage generation, the hybrid composite containing 2 wt.% of MoS2/ZnO facilitated almost 20 times higher performance (peak‐to‐peak voltage of 2.4 V). This work yielded a phase‐separated composite that finds uses in energy harvesting, sensors, and actuators, among other fields.Highlights NIPS creates high‐porosity composites with improved charge distribution. Layered TMDs improve charge‐transfer mechanism and PVDF's electrical properties. 2 wt.% MoS2/ZnO exhibits nearly 20 times higher voltage generation than neat PVDF.

Uniaxial and biaxial experimental investigation of glassy polymers

The alignment of polymer chains within polycarbonate (PC) significantly influences the mechanical properties of the deformed specimen. This influence can be affected by both the global stretch rate and the type of loading. The objectives of the current work are to investigate uniaxial film, bar specimens, and biaxial thick-walled specimens using 3D-optical measurements.Our approach involves developing different methods to determine the local inhomogeneous strain fields for both thin and thick-walled uniaxial specimens. In the pure tension case and under the assumption of uniaxial plane stress, we utilize the strains to calculate the local volume ratio and, consequently, approximate the local true stress at different axial positions of the specimen. Additionally, we investigate the effect of variations in global stretch rates on local stresses. Furthermore, we explore induced anisotropy for different global stretching ratios.Another objective is to investigate biaxial specimens under sequential and simultaneous biaxial stretching conditions, examining the impact of both stretching types on the mechanical and structural properties of the material.

Electrically regulated thermal conductivity of aramid polymer systems

Aramid polymers, renowned for their electronic insulation and thermal conductive properties, are widely adopted as thermal management materials in power electronics. However, the thermal conductivity of aramid polymers under electric field has not been thoroughly understood. In this study, we investigated the thermal conductivity of amorphous and aligned aramid polymer systems under electrical field utilizing equilibrium molecular dynamics simulations. Simulation results showed that the alignment of polymer chain can significantly enhance the thermal conductivity of aramid polymer systems, achieving up to 10.13 W/m-K. Moreover, polarization of aligned aramid polymer was observed when the applied electric field exceeded 14 V/nm. Interestingly, the thermal conductivity of aligned aramid polymer was selectively modulated by the applied electric field. To unravel the underlying phonon mechanism, the molecular orientation of polymer chains and phonon spectral information were analyzed. Our study provides guidance into understanding thermal transport mechanism and thermal conductivity modulation in polymers.

A highly aligned X-shaped hydrogel fiber via cooperative roles of amorphous and crystalline network mediated by Hofmeister effect

Achieving high alignment of polymer chains is highly desirable for hydrogels as structural materials, but challengeable. Here, based on Hofmeister effect, a cooperative regulation strategy simultaneously using salting-in and salting-out salts (CSS) is proposed to fabricate well aligned X-shaped hydrogel fibers. First, the freeze-resistant and salting-in salt depresses the growth of ice, inducing an amorphous network for freeze–thawed hydrogel. Combined with further densified polymer chains, extension ability of raw hydrogel reaches maximum extent and thus makes large prestretching strain available during stretching orientation. Second, a salting-out salt effectively fixes the aligned structures via triggering the approach of polymer chains, accompanied with enhanced crystallinity and H-bonds. Notably, the salting-out effect induces symmetrical diffusion of water, spontaneously generating a X-shaped cross-section with skin–core structure. These cooperative roles of amorphous and crystalline network mediated by Hofmeister effect also provide possibility for twisted hydrogel fibers with greatly improved load-bearing capacity.

Driving fiber diameters to the limit: nanoparticle-induced diameter reductions in electrospun photoactive composite nanofibers for organic photovoltaics

Electrospun photoactive nanofibers hold significant potential for enhanced photon absorption and charge transport in organic photovoltaics. However, electrospinning conjugated polymers with fiber diameters comparable to exciton diffusion lengths for efficient dissociation, is difficult. Previously, spinning sub-100 nm poly(3-hexylthiophene) (P3HT) fibers has required the auxiliary polymer, poly(ethylene oxide) (PEO), and large antisolvent additions. Therefore, its success differs considerably across donor polymers, due to variable antisolvent addition limits before precipitation. Herein, plasmonic nanoparticle infusion into P3HT nanofibers is used to modulate viscosity and deliver a novel and unrivaled strategy to achieve reduced fiber diameters. Following PEO removal, the fibers measure 55 nm in diameter, 30% lower than any previous report – providing the shortest exciton diffusion pathways to the heterojunction upon electron acceptor infiltration. The nanoparticle-containing nanofibers present a 58% enhancement over their pristine thin-film counterparts. ~17% is ascribed to plasmonic effects, demonstrated in thin-films, and the remainder to along-fiber polymer chain alignment, introduced by electrospinning. The anisotropy of light absorbed when polarized parallel versus perpendicular to the fibers increases from 0.88 to 0.62, suggesting the diameter reduction improves the alignment, resulting in greater electrospinning-induced enhancements. Controlled by the electrospinning behavior of PEO, our platform may be adapted to contemporary donor-acceptor systems.Graphical A dramatic reduction in the diameters of electrospun photoactive nanofibers is achieved by introducing nanoparticles, offering shorter exciton pathways towards the heterojunction in nanofibrous OPVs. Thinner fiber diameters enhance the alignment of the polymer chains along the fiber, manifesting in greater photon absorption. Alongside plasmonic effects, the dual-mode enhancement within the fibers offers 58% additional light harvesting versus their thin-film counterparts.

Enhancing the Piezoelectric Properties of 3D Printed PVDF Using Concurrent Torsional Shear Strain.

Extrusion-based polymer 3D printing induces shear strains within the material, influencing its rheological and mechanical properties. In materials like polyvinylidene difluoride (PVDF), these strains stretch polymer chains, leading to increased crystallinity and improved piezoelectric properties. This study demonstrates a 400% enhancement in the piezoelectric property of extrusion-printed PVDF by introducing additional shear strains during the printing process. The continuous torsional shear strains, imposed via a rotating extrusion nozzle, results in additional crystalline β-phases, directly impacting the piezoelectric behavior of the printed parts. The effect of the nozzle's rotational speed on the amount of β-phase formation is characterized using FTIR. This research introduces a new direction in the development of polymer and composite 3D printing, where in-process shear strains are used to control the alignment of polymer chains and/or in-fill phases and the overall properties of printed parts.