Polymer Bilayer Research Articles

Microstructures in All-Inkjet-Printed Textile Capacitors with Bilayer Interfaces of Polymer Dielectrics and Metal-Organic Decomposition Silver Electrodes.

Soft printed electronics exhibit unique structures and flexibilities suited for a plethora of wearable applications. However, forming scalable, reliable multilayered electronic devices with heterogeneous material interfaces on soft substrates, especially on porous and anisotropic structures, is highly challenging. In this study, we demonstrate an all-inkjet-printed textile capacitor using a multilayered structure of bilayer polymer dielectrics and particle-free metal-organic decomposition (MOD) silver electrodes. Understanding the inherent porous/anisotropic microstructure of textiles and their surface energy relationship was an important process step for successful planarization. The MOD silver ink formed a foundational conductive layer through the uniform encapsulation of individual fibers without blocking fiber interstices. Urethane-acrylate and poly(4-vinylphenol)-based bilayers were able to form a planarized dielectric layer on polyethylene terephthalate textiles. A unique chemical interaction at the interfaces of bilayer dielectrics performed a significant role in insulating porous textile substrates resulting in high chemical and mechanical durability. In this work, we demonstrate how textiles' unique microstructures and bilayer dielectric layer designs benefit reliability and scalability in the inkjet process as well as the use in wearable electronics with electromechanical performance.

Ordering in Dewetting of a Thin Polymer Bilayer with a Topographically Patterned Interface

Ordering in Dewetting of a Thin Polymer Bilayer with a Topographically Patterned Interface

Fabrication of Robust Capsules by Sequential Assembly of Polyelectrolytes onto Charged Liposomes.

This work presents a simple methodology for coating small unilamellar liposomes bearing different degrees of positive charge with polyelectrolyte multilayers using the sequential layer-by-layer deposition method. The liposomes were made of mixtures of 1,2-dioleyl-sn-glycero-3-phosphocoline and dimethyl dioctadecyl ammonium bromide (DODAB) and coated by alternated layers of the sodium salt of poly(4-styrenesulfonate) (PSS) and poly(allylamine) (PAH) as polyanions and polycations, respectively. The results show that the zeta potential of the liposomes was not very sensitive to the mole fraction of DODAB in the membrane, XD, in the range 0.3 ≤ XD ≤ 0.8. We were able to coat the liposomes with up to four polymer bilayers. The growth of the capsule size was followed by dynamic light scattering, and in some cases, by cryo-transmission electron microscopy, with good agreement between both techniques. The thickness of the layers, measured from the hydrodynamic radius of the coated liposome, depends on the polyelectrolyte used, so that the PSS layers adopt a much more packaged conformation than the PAH layers. An interesting finding is that the PSS amount needed to reach the isoelectric point of the capsules increases linearly with the charge density of the bare liposomes, whereas the amount of PAH does not depend on it. As expected, the preparation of the multilayers has to be done in such a way that when the system is close to the isoelectric point, the capsules do not aggregate. For this, we dropped the polyelectrolyte solution quickly, stirred it fast, and used dilute liposome suspensions. The method is very flexible and not limited to liposomes or polyelectrolyte multilayers; also, coatings containing charged nanoparticles can be easily made. Once the liposomes have been coated, lipids can be easily eliminated, giving rise to polyelectrolyte nanocapsules (polyelectrosomes) with potential applications as drug delivery platforms.

Strain history of 3D printed bilayer structure with flexible elastomer and shape memory polymer filaments during thermal tensile test

This study aimed to investigate the strain history of a 3D-printed shape-memory polymer (SMP) and elastomer bilayer specimen under thermal tensile load. First, printing conditions for producing single-layer and bilayer specimens using a fused deposition modeling 3D printer were determined. Tensile tests under thermal effects were then conducted on both specimens. A 1 kg weight was used as a constant tensile load, and temperature cycles ranging from 25 to 65 °C were implemented to determine the thermal effects. The strain history was measured using a strain gauge attached to the specimen during the tests. An initial bending deformation caused by the shrinkage of the elastomer layer was observed in the bilayer specimen immediately after printing. This initial bending was then removed from the bilayer specimen via uniform heating. Strain relaxation was observed in the strain history of the single-layer SMP specimen. Mismatch strain between the two layers of the bilayer specimens was also confirmed from the thermal tensile test results. Analyses and discussions on the strain history data are provided in this paper. In general, this study determined the empirical deformation characteristics of a 3D-printed SMP–elastomer bilayer structure under combined thermal and tensile loading conditions. The results can be used to comprehend the deformation of bilayer SMP–elastomer structures and will be useful for designing a bilayer structure made of 3D-printed SMP material.

Electrodeposition of conductive PAMT/PPY bilayer composite coatings on 316L stainless steel plate for PEMFC application

Stainless steel fulfills most of the requirements as bipolar plates in Proton Exchange Membrane Fuel Cell. However, it undergoes severe corrosion in fuel cell operating condition. This can be resolved by coating the stainless steel with corrosion resistive conducting polymers. In this study, homogeneous and adherent conductive Poly(2-amino-5-mercapto-1,3,4- thiadiazole)/Polypyrrole (PAMT/PPY) mono and bilayer polymer composite coatings are electrosynthesized on 316L SS in 0.5 M H2SO4 by cyclic voltammetry and chronopotentiometry. The hydrophobicity and surface morphology of the coatings are analyzed by contact angle and scanning electron microscopy respectively. The polymer coatings are evaluated in 0.5 M H2SO4 medium by potentiodynamic polarization and impedance techniques at 25 °C. The polarization results reveal that PAMT on PPY composite coating shifts the Ecorr of the 316L SS towards noble direction. The EIS study reveals that the Rf value of PAMT on PPY coating is significantly higher by three orders (x103 Ωcm2) of magnitude than uncoated 316L SS. The corrosion performance of the coatings in simulated PEMFC environment is investigated by potentiodynamic and potentiostatic studies. Results show that the PAMT on PPY and PPY on PAMT bilayer coatings are stable and increased the corrosion potential by about 410–470 mV and 275–310 mV (SCE) in simulated cathodic and anodic conditions respectively. This investigation reports that the PAMT on PPY bilayer coating is serving as a good physical barrier and protecting the 316L SS against corrosion in PEMFC environment.

A Polymeric Bilayer Multi-Legged Soft Millirobot with Dual Actuation and Humidity Sensing.

There are numerous works that report wirelessly controlling the locomotion of soft robots through a single actuation method of light or magnetism. However, coupling multiple driving modes to improve the mobility of robots is still in its infancy. Here, we present a soft multi-legged millirobot that can move, climb a slope, swim and detect a signal by near-infrared irradiation (NIR) light or magnetic field dual actuation. Due to the design of the feet structure, our soft millirobot incorporates the advantages of a single actuation mode of light or magnetism. Furthermore, it can execute a compulsory exercise to sense a signal and analyze the ambience fluctuation in a narrow place. This work provides a novel alternative for soft robots to achieve multimode actuation and signal sensing.

Stable polymer bilayers for protein channel recordings at high guanidinium chloride concentrations

The use of chaotropic reagents is common in biophysical characterization of biomolecules. When the study involves transmembrane protein channels, the stability of the protein channel and supporting bilayer membrane must be considered. In this letter, we show that planar bilayers composed of poly(1,2-butadiene)-b-poly(ethylene oxide) diblock copolymer are stable and leak-free at high guanidinium chloride concentrations, in contrast to diphytanoyl phosphatidylcholine bilayers, which exhibit deleterious leakage under similar conditions. Furthermore, insertion and functional analysis of channels such as α-hemolysin and MspA are straightforward in these polymer membranes. Finally, we demonstrate that α-hemolysin channels maintain their structural integrity at 2 M guanidinium chloride concentrations using blunt DNA hairpins as molecular reporters.

Effect of Detergents on Morphology, Size Distribution, and Concentration of Copolymer-Based Polymersomes.

Polymersomes made of amphiphilic diblock copolymers are generally regarded as having higher physical and chemical stability than liposomes composed of phospholipids. This enhanced stability arises from the higher molecular weight of polymer constituents. Despite their increased stability, polymer bilayers are solubilized by detergents in a similar manner to lipid bilayers. In this work, we evaluated the stability of poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-PCL)-based polymersomes exposed to three different detergents: N-octyl-β-d-glucopyranoside (OG), lauryldimethylamine N-oxide (LDAO), and Triton X-100 (TX-100). Changes in morphology, particle size distribution, and concentrations of the polymersomes were evaluated during the titration of the detergents into the polymersome solutions. Furthermore, we discussed the effect of detergent features on the solubilization of the polymeric bilayer and compared it to the results reported in the literature for liposomes and polymersomes. This information can be used for tuning the properties of PEG-PCL polymersomes for use in applications such as drug delivery or protein reconstitution studies.

Bilayer polymer dielectric systems for high response NO2 gas sensors

In this study, the effects of bilayer polymer dielectric systems on the characteristic of nitrogen dioxide (NO2) gas sensors and organic field effect transistor (OFET) were investigated. Different bilayer polymer dielectrics were obtained by depositing polymethyl methacrylate (PMMA) films on monolayer polystyrene (PS), polyvinyl pyrrolidone (PVP), or PMMA films by spin coating. The responsivity of PS/PMMA-based sensors to 30 ppm NO2 gas is up to 7633%, which is 35.7% higher than that of PMMA/PMMA-based sensors. Meanwhile, the sensitivity to NO2 gas has increased from the lowest 191%/ppm to 265%/ppm. The copper phthalocyanine (CuPc) film on PS/PMMA dielectric layer is induced to form more gaps between the rod domains, which are favorable to the gas interaction. The response mechanism was proposed that the equivalent three-dimensional sensing films caused by multi-layer polymer dielectrics play a significant role in the remarkable increase of gas response.

Magnetocaloric actuation of soft polymer robots

We report a polymer bilayer actuator that is capable of transducing magnetic effects into heat energy in an electromagnetic field and in this way shows various controllable motions.

Interfacial polarization-induced high-k polymer dielectric film for high-performance triboelectric devices

Output performance of triboelectric devices critically depends on their surface charge density that is greatly influenced by the dielectric constant of material. However, contrary to polymer composites, the dielectric constant cannot be substantially increased in pure polymers. This study shows that interfacial polarization in bilayer polymer films significantly enhances their dielectric constants, increasing the surface charge density and triboelectric performance. This is the first report of the introduction of interfacial polarization of dielectric materials for the enhancement of triboelectric output performance. The elastic bilayer films consisting of polydimethylsiloxane (PDMS) coated with poly (2,2,2-trifluoroethyl methacrylate) (PTF) and poly (L-lysine) (PLL) as negative and positive triboelectric materials, respectively, are utilized in triboelectric devices, which show a dramatic increase in the dielectric constants (24.4 for PTF-PDMS and 15.2 for PLL-PDMS bilayers at 10 kHz) through interfacial polarization, resulting in significant enhancement of triboelectric performance when compared with hard single-layer films. For proofs of concept, we fabricated a temperature-sensitive triboelectric sensor and vibration-based triboelectric nanogenerator. The sensor showed the highest temperature sensitivities among triboelectric sensors whereas the nanogenerator provided vibration-induced sustainable power for LED operation without rectification, which was attributed to the charge accumulation in the bi-layered dielectric films.

High-performance near-infrared polymeric phototransistors realized by combining cross-linked polymeric semiconductors and bulk heterojunction bilayer structures

Flexible polymeric phototransistors highly responsive to near-infrared (NIR) light are crucial for the room temperature biological imaging due to some unique properties of organic semiconductors, such as light weight, low cost, and good biocompatibility. However, the low mobility and/or the high dark off-current (DOC) of low-bandgap polymeric phototransistors limit their NIR light detectability. This work proposes the development of a solution-processable bilayer heterostructure (BHS) for polymeric phototransistors, which uses cross-linked polymeric semiconductors (CLPS) as the bottom conducting channel and a bulk heterojunction (BHJ) as the photoactive layer. The BHS architecture ensures fast carrier transport and efficient exciton separation. Besides, the electron-trapping effect generated between the CLPS and BHJ results in a significantly lower DOC compared with other controlled devices. Thus, the BHS phototransistor based on low-bandgap polymer can detect NIR light with wavelengths of 808 nm, 1064 nm, and even 1550 nm, going from NIR-I (750–1000 nm) to NIR-II (1000–1700 nm). Meanwhile, its responsivity (R) is two or three orders of magnitude higher than the controlled device. Furthermore, an ultra-flexible NIR phototransistor array (~5 μm thick) using this strategy could detect image barcodes with different gray levels, demonstrating its potential application in flexible NIR imaging.

Interfacial adhesion and self-healing kinetics of multi-stimuli responsive colorless polymer bilayers

Simple self-healing behavior of polymers that respond to multiple physicochemical stimuli are highly desirable for industrial applications. In this study, under various external environmental stimulating factors, we focus on the self-healing kinetics of polymer bilayer films (PBFs) comprising a colorless polyimide (CPI) bottom-substrate layer and linseed oil loaded microcapsule (LOMC)-embedded polydimethylsiloxane (PDMS) upper-healing layer. The experimental results showed clear correlation between stimulating factors and the healing time. Although the crack-healing behavior of PBF with 5 wt% microcapsule under air atmosphere is fairly slow, it has an improved healing effect at the artificial crack interface heating to 70 °C; moreover, gradual healing is observed by moisture absorption in environments with relative humidity of 70%. Remarkably, we found that ultraviolet (UV)-light irradiation through the 5 wt% LOMC-filled PDMS layer triggers a noticeable kinematic advantage for the drying reaction that initiates interfacial self-healing. Short-time (20 min) UV-irradiated PBF 5 wt% exhibits a low water vapor permeability of 35.4 g m−2 day−1 and excellent healability with ~91% recovery by single capsule-type photochemical-induced self-healing. The proposed approach advances the extrinsic healing of colorless polymers in a kinetically effective way without compromising their chemical composition.

Universal dynamics of coarsening during polymer-polymer thin-film spinodal dewetting kinetics.

The dewetting dynamics of a supported bilayer polymer thin film on a solid substrate is investigated using grazing incidence x-ray photon correlation spectroscopy. We find that the top layer dewets via the spinodal mechanism. The kinetics of the dewetting is studied by monitoring the time evolution of the surface diffuse x-ray scattering intensity. We study the time evolution of fluctuations about the average surface structure by measuring the two-time x-ray intensity fluctuation correlation functions. Using these two-time correlation functions we quantify the crossover from early-time diffusive dynamics to hydrodynamics. The early diffusive regime satisfies dynamic universality. The two-time correlation functions also quantify the onset of hydrodynamic effects. The hydrodynamic regime is observed during the spinodal dewetting process as these interactions are not screened.

Investigating the Mechanisms of AquaporinZ Reconstitution through Polymeric Vesicle Composition for a Biomimetic Membrane.

Aquaporin-Z (AqpZ) are water channel proteins with excellent water permeability and solute rejection properties. AqpZ can be reconstituted into vesicles utilizing cell-like bilayer membranes assembled from amphiphilic block copolymers, for the preparation of high-performance biomimetic membranes. However, only a few copolymers have been found suitable to act as the membrane matrix for protein reconstitution. Hence, this work analyzes the mechanism of protein reconstitution based on a composition-reconstitution relationship. The vesicle formation and AqpZ reconstitution processes in various amphiphilic block copolymers were investigated in terms of size, morphology, stability, polymeric bilayer membrane rigidity, and thermal behavior. Overall, this study contributes to the understanding of the composition-reconstitution relationship of biomimetic membranes based on AqpZ-reconstituted polymeric vesicles.

ZnO/conducting polymer bilayer via sequential spin-coating for enhanced UV sensing

Zinc oxide (ZnO) has been widely investigated as an important ultraviolet (UV) sensing material in view of its wide band gap (~3.4 eV). However, the fabrication of continuous thin films of ZnO generally requires complex, time-consuming, and expensive processes, such as sputtering and atomic layer deposition. Herein, we demonstrate a bilayer film consisting of a conducting polymer and ZnO nanoparticles sequentially deposited using a simple, rapid, and inexpensive two-step spin-coating process. In this approach, it is not necessary to have a continuous ZnO nanoparticle film as the active layer, because the conducting polymer deposited under the ZnO nanoparticles acts as a conductive and continuous supporting layer for the particles. Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) is used as the auxiliary layer to promote the efficient transport of photo-carriers generated from ZnO nanoparticles under UV light. As a result, under UV light (365 nm), photocurrents obtained from a ZnO/PEDOT: PSS bilayer film are significantly higher (∼20 times) than that from a ZnO layer for a given voltage bias. The photoelectric performance can be further tuned by controlling the speed of spin-coating in the deposition of ZnO nanoparticles. The stability and photo response (rise and decay time) of the ZnO/PEDOT: PSS bilayer film under the repeated on-off condition are also reported.

Stimuli-Responsive Shape Changing Commodity Polymer Composites and Bilayers.

Commodity polymers are produced in large volumes, providing robust mechanical properties at relatively low costs. The products made from these commodity polymers typically offer only static functionalities. Over the past decade, however, in the scientific literature, stimuli-responsive additives and/or polymer coatings have been introduced to commodity polymers, yielding composites and bilayers that change shape in response to light, temperature, and/or humidity. These stimuli responsive commodity polymers allow the marketing and sales of these otherwise bulk products as “high-end” smart materials for applications spanning from soft actuators to adaptive textiles. This Spotlight on Applications presents an overview of recent intriguing works on how shape changing commodity polymer composite and bilayer actuators based on polyamide 6, poly(ethylene terephthalate), polyethylene, and polypropylene have been fabricated that respond to environmental stimuli and discusses their potential applications.

Principles Governing Control of Aggregation and Dispersion of Graphene and Graphene Oxide in Polymer Melts.

Controlling the structure of graphene and graphene oxide (GO) phases is vitally important for any of its widespread intended applications: highly ordered arrangements of nanoparticles are needed for thin-film or membrane applications of GO, dispersed nanoparticles for composite materials, and 3D porous arrangements for hydrogels. By combining coarse-grained molecular dynamics and newly developed accurate models of GO, the driving forces that lead to the various morphologies are resolved. Two hydrophilic polymers, poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA), are used to illustrate the thermodynamically stable morphologies of GO and relevant dispersion mechanisms. GO self-assembly can be controlled by changing the degree of oxidation, varying from fully aggregated over graphitic domains to intercalated assemblies with polymer bilayers between sheets. The long-term stability of a dispersion is extremely important for many commercial applications of GO composites. For any degree of oxidation, GO does not disperse in PVA as a thermodynamic equilibrium product, whereas in PEG dispersions are only thermodynamically stable for highly oxidized GO. These findings-validated against the extensive literature on GO systems in organic solvents-furnish quantitative explanations for the empirically unpredictable aggregation characteristics of GO and provide computational methods to design directed synthesis routes for diverse self-assemblies and applications.

A bilayer polymer electrolyte encompassing pyrrolidinium-based RTIL for binder-free silicon few-layer graphene nanocomposite anodes for Li-ion battery

A binder-free electrode made of polycrystalline carbon-coated silicon nanoparticles encapsulated in few-layer graphene flakes is coupled with a PEO-based crosslinked bilayer polymer electrolyte (BLPE). A soft polymer electrolyte layer enriched with a pyrrolidium-based ionic liquid (Pyr14TFSI) is deposited on top of the electrode and UV cured by an in situ process to achieve optimal interfacial contact. A hard layer consisting of a crosslinked PEO-based polymer electrolyte film with a lower amount of Pyr14TFSI is integrated with the electrode/electrolyte assembly to improve the self-standing and shape-retention abilities. Proof-of-concept lab-scale Si-C||Li-metal polymer cells demonstrate a reversible specific discharge capacity up to 1044 mAh gSi–1 at 80 °C, largely outperforming the one with Pyr14TFSI/LiTFSI liquid electrolyte under the same experimental condition. Our results highlight the beneficial effect of the crosslinked PEO-based polymer matrix on the cycling performance, despite the absence of any SEI-forming agent.

Electrohydrodynamic instability: effect of rheological characteristics on the morphological evolution of liquid crystal–polymer interface

Electrohydrodynamic instability, in a polymer–air or polymer–polymer bilayer settings, gives rise to the formation of the ordered micropillars or microwells at the initial planar interface. It is well known that the complex interplay among the controlling parameters, such as the intensity of the electrostatic field, film thickness, interfacial tension and dielectric constants of the layers determine the morphology of the interface. In this report, for the first time, experimentally it is shown that rheological property of the lower polymer layer [here, polydimethylsiloxane (PDMS)] has a significant influence on the morphological evolution. We probe the kinetic time scale of the evolution by inducing fast destabilization of the interface due to the high dielectric contrast between two layers (liquid crystal–PDMS) and reduced interfacial tension. At this time scale, it was demonstrated that micropillars are formed for thin viscoelastic ‘soft’ PDMS film, whereas microwells were observed for viscoelastic ‘hard’ film in similar settings. A transition from micropillar to microwell was observed for viscoelastic ‘soft’ film when the thickness of the film increased from $${\sim } 4$$ to $$11\,\upmu \hbox {m}$$ . Based on this observation, by controlling the rheological properties, different patterns were developed from similar templated PDMS substrates.