Polymer Films Research Articles

Functional Protective Coatings Based on Polysaccharides and Single-Ion Conducting Polymers for Li Metal Batteries

This work aims to study a protective coating based on cellulose and P(LiMTFSI) single-ion conductor polymer and its effects on Li metal anode stability and reversibility. The strategy used involves the physical mixture of the aforementioned polymers to enhance the electrochemical performance through Li-ion flux homogenization at the Li metal surface, promoting the formation of a dense plating. Single-ion conducting polymers (SICPs) are incorporated due to their beneficial effects such as enhancing lithium ion transport, boosting lithium transference number (𝑡𝐿𝑖 +), and diminishing the effects of concentration polarization, avoiding the initiation and propagation of high surface area lithium (HSAL). Furthermore, a quasi-solid-state Li metal battery system is explored which brings additional advantages over the typically used organic electrolytes. In this sense, during this study we propose using the protective coating based on cellulose and P(LiMTFSI) to tailor an adequate interphase that creates a good adhesion, by taking advantage of the polymers film formation ability, and therefore improving the lifespan and safety of the battery. The coating effectiveness is tested by casting the solution on an activated lithium surface and performing lithium platting/stripping protocols in Li/Li and Li/Cu pouch cells under selected current densities (0.5, 1 and 2 mA/cm2). Complementary electrochemical tests are carried out to study transport, conductivity parameters, and its performance in full cell coupled with LFP cathode. Finally, we analyze the correlation with the physicochemical properties and electrochemical performed based on spectroscopic techniques and microscopy to study the most relevant parameters influencing a high Coulombic Efficiency. Acknowledgments This work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska – Curie Grant Agreement N° 945357, and co-financing from the Slovenian Research and Innovation Agency (ARIS) is fully acknowledged.

Pinning Forces on the Omniphobic Dry, Liquid-Infused, and Liquid-Attached Surfaces.

Omniphobic coatings effectively repelling water, oils, and other liquids are of great interest and have a broad number of applications including self-cleaning, anti-icing surfaces, biofouling protection, selective filtration, etc. To create such coatings, one should minimize the pinning force that resists droplet motion and causes contact angle hysteresis. The minimization of the free surface energy by means of the chemical modification of the solid surface is not enough to obtain a nonsticky slippery omniphobic surface. One should minimize the contact between the solid and the droplet. Besides coating the surface with flat polymer films, among the major approaches to create omniphobic coatings, one can reveal "lotus effect" textured coatings, slippery liquid-infused porous surfaces (SLIPS), and slippery omniphobic covalently attached liquid (SOCAL) coatings. It is possible to turn one surface type into other by texturizing, impregnating with liquids, or grafting flexible liquid-like polymer chains. There are a number of models describing the pinning force on surfaces, but the transitions between states with different wetting regimes remain poorly understood. At the same time, such studies can significantly broaden existing ideas about the physics of wetting, help to design coatings, and also contribute to the development of generalized models of the pinning force. Here we review the existing pinning force (contact angle hysteresis) models on various omniphobic substrates. Also, we discuss the current studies of the pinning force in the transitions between different wetting regimes.

Expanding the Materials Palette for Organic Electrochemical Transistor Channels Via Electropolymerization and Functionalized Pyrrole, Thiophene, and Aniline Monomers

Electrochemical transistors are electrolyte-gated devices that permit large signal amplification, ionic-to-electronic signal transduction, and controlled variable resistance. Given that their porous channel materials enable volumetric interaction with the adjacent electrolyte, OECT offer increased detection sensitivity compared to other electrolyte-gated devices such as field-effect transistors (FET).Although these OECT devices have demonstrated utility in a wide range of applications, from neuromorphic computing platforms to bioelectronic devices, they are still in an early stage of development. As a result, a limited range of channel materials have been investigated. Because the magnitude of signal amplification in OECT is directly proportional to the channel transconductance, the vast majority of OECT studies have employed highly-conductive spin-coated formulations of polyethylenedioxythiophene:poly(styrene sulfonate) (PEDOT:PSS) as the active material. While PEDOT-PSS exhibits many desirable qualities for an OECT channel material (e.g., biocompatibility, high transconductance, relatively low mechanical modulus, and responsivity to aqueous ions and bioanalytes), the material has general susceptibility to changes in the ionic strength of the solution it is measuring, which limits its utility for ion-specific detection and in systems for which changes in ionic strength necessarily accompany the other specific changes that the OECT seeks to detect or influence (i.e. neurotransmitter detection). In addition, the material is almost exclusively deposited via spin-coating, which requires a premade solution of pre-determined physical characteristics (concentration, molecular weight, dopant-to-monomer ratio), and therefore limits the ability to for higher-throughput investigation of wide varieties of material configurations.Although electropolymerization of conducting polymers like polypyrrole, polythiophene, and polyaniline is well-studied, only a few isolated reports1,2 have evaluated the benefits of electropolymerization for OECT channel fabrication and performance (i.e., compared to spin-coating or vapor-phase polymerization). However, in a more general sense, electropolymerization provides several additional advantages for OECT channel fabrication:(1) reduce the total time and cost associated with device preparation by reducing the total number of required microfabrication steps;(2) permit higher-throughput methods for fabricating channels with diverse characteristics and dopants;(3) use dopants that allow operation in either depletion or accumulation mode (versus spin-coated PEDOT-PSS, which operates only in depletion mode);(4) enable facile control over channel thickness and form-factor during synthesis;(5) increase control over material properties that influence both electronic and ionic conductivity, such as polymer chain length/stiffness, spacing, and electrostatic affinity;(6) provide a strategy for using electrochemical synthesis to tune the channel transconductance.Unfortunately, there have so far been only isolated repots of electropolymerized OECT channels, and no systematic studies. In this report, our research team will demonstrate the effect of electrosynthesis parameters on channel material characteristics and device performance (i.e., total channel capacity, transconductance, ionic/electronic conductivity, and overall electrochemical impedance). We examined the influence of electrodeposition method (galvanostatic, potentiostatic, linear sweep voltammetry), monomer type, the total degree of polymerization, and the dopant used during electrosynthesis (comparing small, labile dopants such as chloride or tosylate, versus larger semi-labile dopants such as dodecyl benzene sulfonate, versus large immobile polymer dopants such as PSS). We also quantify the impact of introducing different functionalities (e.g., amine, carboxy, sulfonic acid) to the pyrrole, aniline, and thiophene monomers used to fabricate the channels). These functionalities provide motifs for addition functionalization (e.g. using carbodiimide chemistry) with enzymes, biorecognition elements, or redox signaling molecules.Finally, we will present the steps we have taken to implement these devices within organ-on-a-chip systems, and demonstrate the utility of our devices for studying the formation and longitudinal evolution of neural networks within in vitro neuronal colonies. References S. Wustoni, T.C. Hidalgo, A. Hama, D. Ohayon, A. Savva, N. Wei, N. Wehbe, S. Inal. In Situ Electrochemical Synthesis of a Conducting Polymer Composite for Multimetabolite Sensing. Adv. Mater. Technol. 2020, 5, 1900943. L. Zhang, T.L. Andrew. Deposition Dependent Ion Transport in Doped Conjugated Polymer Films: Insights for Creating High-Performance Electrochemical Devices. Adv. Mater. Interfaces 2017, 4, 1700873.

3D Porous Silver Nonwoven Mat Prepared with Cellulosic Templates and Spray Equipment for Supercapacitor Current Collectors

Supercapacitors are energy conversion devices with higher power density compared to batteries and higher energy density compared to common capacitors.[1] These particular properties have attracted considerable attention with regard to numerous applications in such diverse fields as power electronics, military equipment, and hybrid electric vehicles (i.e. HEVs, in order to help the stop and go function and to provide peak power for improved acceleration).[2] In addition, supercapacitors can play an important role in complementing the energy storage functions of batteries and fuel cells by providing back-up power supplies to protect against power disruptions.[3,4]Supercapacitors have four major components, namely, current collectors, electrodes, electrolytes and separators.[3] However, although electrodes have been actively studied, there are far fewer studies of current collectors than the other there components. Typical current collectors are nickel (Ni), platinum (Pt), gold (Au), aluminum (Al), silver (Ag) and copper (Cu). Although Ag compared with the other materials offers many advantages including high current-carrying capability (i.e., lowest resistivity at 1.63 x 10-8 Ωm)[5] and good chemical and thermal stability,[6] Ag current collectors are rarely used in supercapacitors. In our previous study, which demonstrated the usefulness of a solution processed Ag current collector in supercapacitors, we used a 2-dimensional (2D) Ag plated polymer film as the current collectors.[7] In this study, we propose a method of enhancing the usefulness of a solution processed Ag current collector by making a 3-dimensional (3D) porous Ag nonwoven mat current collector from the cellulosic template in order to maximize the efficiency of the Ag current collector. This may have the result of maximizing the contact area between the electrode and the electrolyte, such as Ni foam.[8] This 3D porous Ag nonwoven mat would be also useful in such applications as the cathodes of alkaline fuel cells owing to its good chemical and thermal stability,[9] and might also be used in a variety of filtration applications where the antimicrobial and antibacterial properties of silver make silver membranes a very efficient filtration system.[10]In this study, we propose a simple method of making a 3D porous silver nonwoven mat as the current collector of supercapacitors, and investigate their super-capacitive properties using cyclic voltammetry in 1 M Na2SO4. For the purpose of comparison, the electrochemical properties of the 2D Ag plated current collector were also investigated. Cellulosic templates were used to make a 3D porous Ag nonwoven mat as the current collector of a supercapacitor with an Ag nanoparticle dispersed solution and simple spray equipment.

Affecting the Electropolymerization of Aniline with Permanent Magnets

As portable electronics become more ubiquitous, the demand for different electrochemical energy storage (EES) systems grows. Conductive-polymer-based supercapacitors are an emerging type of EES device promising for their rapid charging and discharging, and among these, polyaniline (PANI) is favored for the ability to deposit it electrochemically from aqueous solutions of monomer. Despite this advantage, supercapacitors fabricated with PANI exhibit poor energy density and cyclability compared to other supercapacitors. In this work, it is shown how a permanent magnet can be applied to affect this electropolymerization, increasing the capacitance of the resultant polymer film by over 70% and increasing its cyclability more than ten-fold. The use of a permanent magnet allows enhancement of the process without the use of any chemical additives or additional energy input, such as from heating, excessive overpotentials, or mechanical stirring. The magnet influences the electropolymerization primarily through the magnetohydrodynamic (MHD) effect, but this work shows that the effect of the magnetic field exceeds that of mechanical stirring. Furthermore, evidence is presented that the influence from the magnet goes beyond forced convection from the MHD effect.

Intelligent Biopolymer-Based Films: Promising New Solutions for Food Packaging Applications.

The development of biopolymer-based films represents a promising direction in the packaging industry that responds to stringent needs for sustainability, reducing the ecological impact. Traditional fossil-derived polymers present major concerns because of their long decomposition time and their significant contribution to the pollution of the environment. On the contrary, biopolymers such as chitosan, PVA, and PLA offer viable alternatives. This study aimed to obtain an innovative pH indicator for smart packaging using a synthetic non-toxic anthocyanin analogue dye incorporated in bio-based films to indicate meat freshness and quality. The pH-responsive color-changing properties of the dye make it suitable for developing intelligent films to monitor food freshness. The obtained polymeric films were characterized by FT-IR and UV-VIS spectroscopy, and their thermal properties were assessed using thermogravimetric methods. Moisture content, swelling capacity, and water solubility of the polymeric films were also evaluated. The sensitivity of the biopolymer-flavylium composite films to pH variations was studied in the pH range of 2 to 12 and noticeable color variations were observed, allowing the monitoring of the meat's quality damage through pH changes. The pH-responsive films were applied directly on the surface or in the proximity of pork and chicken meat samples, to evaluate their colorimetric response to fresh and spoilt meat. This study can be the starting point for creating more durable packaging solutions leading to a circular economy.

Biosynthesis of High Toughness Poly(3-Hydroxypropionate)-Based Block Copolymers With Poly(D-2-Hydroxybutyrate) and Poly(D-Lactate) Segments Using Evolved Monomer Sequence-Regulating Polyester Synthase.

This study synthesized poly(3-hydroxypropionate) [P(3HP)]-containing polyhydroxyalkanoate (PHA) block copolymers, P(3HP)-b-P[2-hydroxybutyrate (2HB)] and P(3HP)-b-P(D-lactate) (PDLA), using Escherichia coli. The cells expressing an evolved sequence-regulating PHA synthase, PhaCARNDFH, and propionyl-CoA transferase were cultured with the supplementation of the corresponding monomer precursors in the medium. The block structure of P(3HP)-b-PDLA was confirmed by proton nuclear magnetic resonance analysis and solvent fractionation. The molecular weights of the polymers were in the range of 0.8-2.8 × 105. The solvent-cast polymer films were subjected to isothermal treatment to promote phase separation and crystallization and were subsequently melt-quenched to produce an amorphous phase. The melt-quenched P(3HP)-b-P(2HB) film exhibited a high elongation at break (1153%), resulting in a toughness of 181 MJ/m3. The solvent-cast film of P(3HP)-b-65 mol% PDLA exhibited partial elastic deformation, in which the P(3HP) phase functioned as a soft segment. The melt-quenching of the polymer resulted in embrittlement presumably due to the high lactate fraction. Overall, the P(3HP)-based block copolymers exhibited several mechanical properties depending on the higher-order structure of the polymer and the properties of the P(2-hydroxyalkanoate) segments. This study findings show that P(3HP)-b-P(2HB) and P(3HP)-b-PDLA can function excellently if their microstructures are properly controlled.

In-plane thermal conductivity measurement of microscale polymer films using a reusable micro-thermocouple

Polymers serve as encapsulating materials for electronic devices, making it crucial to investigate their thermophysical properties. In this work, a novel 2ω method for assessing the in-plane thermal conductivity of polymer films is proposed. A reusable micro-thermocouple, serving as both a heating wire and a sensor, is used with silver paste as the interstitial material in contact with the test film. By comparing the 2ω voltages under both contact and non-contact conditions, the thermal impedance is determined. The thermal conductivity is directly calculated by determining the slope of the real part of the thermal impedance against the logarithm of frequency. Theoretical analysis shows that the influences of contact thermal resistance and radiation heat loss are negligible. To validate the accuracy of the method, measurements were repeated on polyimide and polyester films under various contact conditions. The results demonstrate consistency and align with those obtained using the laser spot periodic heating technique.

Binaphthalene-Assisted Axial Chirality in Porphyrins: Toward Solid-State Circularly Polarized Luminescence from Self-Assembled Nanostructures.

Circularly polarized luminescence (CPL) is emerging as an effective tool to study the excited-state optical activity in molecules and their self-assembled nanostructures. Chiral porphyrins are a class of optically active molecules wherein the ground-state chirality has been extensively studied in recent times using circular dichroism (CD) spectroscopy. However, obtaining CPL from porphyrin nanostructures, which would have vast implications in biological applications, has remained an uphill task. In this work, we design and synthesize a pair of chiral porphyrin enantiomers functionalized by axially chiral binaphthalene units at the four meso-positions. The molecule undergoes self-assembly following an isodesmic polymerization model, leading to the formation of a spherical nanostructure possessing opposite chirality. Favorable thermodynamic parameters achieved through the controlled experimental conditions helped drive the self-assembly in the forward direction. The limitations imposed by a large nonradiative decay constant arising due to the aggregation-induced quenching could be overcome by fabricating self-standing polymeric films of the nanostructures. The films exhibited relatively high radiative decay and, more interestingly, good CPL activity with clear mirror image spectra for the nanostructures with opposite chirality. The work on CPL-active solid-state materials opens avenue for the design and synthesis of a variety of porphyrin-based chromophoric systems and their nanoaggregates that can find potential application in the field of chiral biosensing and bioimaging, security tags, and display devices.

A Facile One-Step Conversion of Biobased Magnolol (Honokiol) toward High Refractive Materials.

A series of polymers with both high refractive index and high Abbe number have been successfully synthesized through the photoclick thiol-ene reaction between the monomers derived from biobased magnolol (or honokiol) and commercial mercaptans and thiophenols. The polymer films not only exhibit a high refractive index and a high Abbe number but also display a transmittance of up to 90% in a range of wavelengths from 550 to 2000 nm and nearly 0% in the UV region. Moreover, these polymers also display low haze values in the visible-light region as well as exhibit good thermostability. These data indicate that they have potential applications for the fabrication of optical lenses and anti-UV coatings. In particular, this series of polymers are readily used for industrialization due to its excellent optical properties but low expense, simplicity, and efficiency of synthesis.

Photo‐Active Soft Actuator Enabling Dynamic Manipulable Lenses with Surface Reshaping

AbstractManipulable lenses with tunable focal length have garnered great attention due to their unique advantages including strong adjustability, low power consumption, fast response times, and ease of integration. However, in the context of advancing intellectualization, weight reduction, and miniaturization of imaging systems, mere focal length adjustment is no longer sufficient. Herein, an innovative method is introduced for creating a dynamic light manipulable (DLM) lens with surface reshaping. This breakthrough is accomplished through the collaborative integration of a medium lens with an actuator based on photo‐active liquid crystal polymer (LCP) film, where the deformation of the photo‐active LCP film can be arbitrarily controlled by meticulously designing the orientation distributions of liquid crystal (LC) mesogens within the film. The lens with three distinct surfaces, including quasi‐cone, paraboloid, and 3 × 3 paraboloid array, are demonstrated with infrared stability, robust fatigue resistance, long natural recovery time, outstanding thermal stability, and excellent solvent resistance, further confirming the feasibility of the lens application in tunable display, imaging, infrared optics, and other systems. This work holds the promise of paving the way for a new generation of imaging systems.

Boosted electro-optic performance in second-order nonlinear optical chromophores featuring thiophen-2-amine-derived donor groups

Two innovative second-order nonlinear optical chromophores, designated as B–C, have been synthesized, featuring thiophene-derived donors and a tricyanovinyldihydrofuran bridge as acceptors. These chromophores have undergone comprehensive characterization. Notably, the donor components of chromophores B–C were (methyl(phenyl)amino)thiophene and (4-methoxyphenylamino)thiophene, respectively, in contrast to the diethylamino phenyl unit present in chromophore A. Density functional theory calculations suggested that the first hyperpolarizability of chromophore C, with a (methoxyphenyl amino) thiophene donor, was approximately 60 % higher than that of chromophores A and B. This indicates that merely substituting the benzene ring with thiophene does not significantly enhance the electron-donating ability of the donor. Polymeric thin films doped with 25 wt% of chromophores A-C exhibited r33 values of 39 p.m./V, 46 p.m./V, and 76 p.m./V, respectively. The electro-optic coefficients of chromophores B and C were 18 % and 95 % higher than that of chromophore A, respectively. These findings confirm that thiophene-derived donors, particularly those with multiple heteroatoms, can effectively enhance the electro-optical coefficient of chromophores.

Voltammetric determination of a UV filter pollutant using a platinum electrode modified by a polymer membrane based on ß-cyclodextrin

Purpose This study aims to develop an electrochemical sensor for the detection of benzophenone (BP) as an alternative to conventional techniques that are known, expensive, complex and less sensitive. Design/methodology/approach The developed sensor is a platinum electrode modified with a plasticized polymer film based on ß-cyclodextrin, using PVC as the polymer, PEG as the plasticizer and ß-CD as the ionophore. This sensor is characterized by various techniques, such as optical microscopy, scanning electron microscopy and cyclic voltammetry. This latter is also used for analyzing kinetic processes at the electrode/electrolyte interface and to evaluate the selectivity and sensitivity of the sensor. Findings The results highlight the performance of our sensor. In fact, it exhibits a linear response extending from 10−19 to 10−13 M, with a correlation coefficient of 0.9836. What is more, it has an excellent detection limit of 10−19 M and a good sensitivity of 21.24 µA/M. Originality/value The results of this investigation demonstrated that the developed sensor is an analytical tool of choice for the monitoring of BP in the aqueous phase. The suggested sensor is fast, simple, reproducible and inexpensive.

An Experimental Study on the Performance of Materials for Repairing Cracks in Tunnel Linings under Erosive Environments

Addressing the current lining cracking problem in coastal tunnels, this paper independently introduces a novel type of repair material for tunnel lining cracks—the composite repair material consisting of waterborne epoxy resin and ultrafine cement (referred to as EC composite repair material). Through indoor testing, we have analyzed the change rule of the mass change rate, compressive strength, flexural strength, and chloride ion concentration of the repair material samples in erosive environments, with the dosage of each component in the EC composite repair material being varied. We have also investigated the working performance, mechanical properties, and microstructure of the repair material. The results of this study show that when the proportion of each component of ultrafine cement, waterborne epoxy resin, waterborne epoxy curing agent, waterborne polyurethane, defoamer, and water is 100:50:50:2.5:0.5:30, the performance of the EC composite repair material in a chloride ion-rich environment is optimal in all aspects. When the mixing ratio of each component of the EC composite repair material is as stated above, the repair material exhibits the best performance in a chloride ion erosion environment. With this ratio of components in the EC composite repair material, the fluidity, setting time, compressive strength, flexural strength, and bond strength of the repair material in a chloride ion erosion environment can meet the requirements of relevant specifications, and it is highly effective in repairing tunnel lining cracks. The polymeric film formed by the reaction between the waterborne epoxy resin emulsion and the curing agent fills the pores between the hydration products, resulting in a densely packed internal structure of EC composite repair material with enhanced erosion resistance, making it very suitable for repairing cracks in tunnel linings in erosive environments.

Multiple Chirality Switching of a Dye‐Grafted Helical Polymer Film Driven by Acid & Base

AbstractA stimuli‐responsive multiple chirality switching material, which can regulate opposed chiral absorption characteristics, has great application value in the fields of optical modulation, information storage and encryption, etc. However, due to the rareness of effective functional systems and the complexity of material structures, developing this type of material remains an insurmountable challenge. Herein, a smart polymer film with multiple chirality inversion properties was fabricated efficiently based on a newly‐designed acid & base‐sensitive dye‐grafted helical polymer. Benefited from the cooperative effects of various weak interactions (hydrogen bonds, electrostatic interaction, etc.) under the aggregated state, this polymer film exhibited a promising acid & base‐driven multiple chirality inversion property containing record switchable chiral states (up to five while the solution showed three‐state switching) and good reversibility. The creative exploration of such a multiple chirality switching material can not only promote the application progress of current chiroptical regulation technology, but also provide a significant guidance for the design and synthesis of future smart chiroptical switching materials and devices.

Harnessing Polar Interactions Tunes the Stability of Ultrathin Polymer Solution Films.

The stability of ultrathin (<100 nm) polymer films is essential in applications like protective coatings. On the contrary, their instability may actually be desirable for the emergence of self-assembled nanoscale patterns utilized in the fabrication of functional devices. Polymer solution films exhibit two distinct kinds of instabilities, viz., dewetting (long-wave) and decomposition (short-wave). Dewetting refers to the rupture of the continuous film to form isolated domains, while decomposition leads to phase separation within the polymer solution. The focus of this work is on leveraging polar interactions between the solute and solvent molecules to tune the stability of the film. A gradient dynamics-based thin film model is developed to investigate pattern formation in a thin polar polymer solution film. The Flory-Huggins theory is suitably modified by introducing a polar interaction parameter that depends upon the concentration of the polymer and the dipole moments of monomer (μ1) and solvent molecules (μ0). A linear stability analysis is performed to determine the characteristic length scale and growth rate of the instabilities. It is shown that the range of concentration space for the occurrence of the decomposition mode is directly affected by the Flory interaction parameter (χ0), μ0, and μ1, thereby serving as control parameters to tune the width of the concentration range. It is further shown that ignoring polar interactions may lead to incorrect predictions of the instability mode, including a complete loss of the decomposition mode. In addition, the long-wave dewetting length scale is found to decrease due to bulk dipolar interactions at higher polymer concentrations. Finally, numerical simulations are carried out to track the nonlinear evolution of the interface and concentration field for both the decomposition and dewetting modes of instability.

Towards strain gauge 2.0: Substituting the electric resistance routinely deposited on polyimide film by the optimal pattern for full‐field strain measurement

AbstractThe checkerboard constitutes the best pattern for full‐field strain measurement because it maximizes image gradient. In the experimental mechanics community, employing this pattern is currently strongly limited because depositing it on the surface of specimens raises practical difficulties. A recent study shows, however, that it is technically possible by using a laser engraver. The present paper aims to push this solution forward by printing a checkerboard pattern on a thin polymeric film and then gluing the resulting laser‐engraved film on the specimen surface. The underlying idea is to separate the manufacturing process of this optical strain gauge on the one hand and its use on the other hand to help spread this strain measuring tool in the experimental mechanics community. The polymeric film employed here is the same as that used in the manufacturing process of classic electrical gauges, so one can rely on the know‐how of classic strain gauge bonding to glue this optical strain gauge on the specimen surface. The main difference between the proposed tool and classic electrical gauges is that the strain field beneath the polymeric support is measured instead of localized strain values. The paper is a proof of concept for this strain field measuring tool. The manufacturing and bonding processes are described in the paper. The localized spectrum analysis, a spectral technique developed for processing images of periodic patterns, is used to retrieve the strain fields from checkerboard images. Through two complementary examples, we show the ability of this new type of strain gauge to detect and quantify local details in the strain field beneath. A simplified 1D model is also proposed to assess the minimum width of the strain peak that can reliably be measured with this technique.

Nitrated benzothiadiazole-based D-A electrochromic polymers with tunable spectral properties

Nitrated benzothiadiazole (BT) is the promising acceptor units in constructing D-A-D electrochromic polymers, but its researches in the electrochromic field was very limited so far. In this work, four kinds of nitrated polymer precursors (Th-NO2-BT, EDOT-NO2-BT, Th-2NO2-BT, and EDOT-2NO2-BT) were synthesized by Stille coupling reaction with EDOT and thiophene units as the end groups (electron donor units) and mono-nitrated benzothiadiazole and di-nitrated benzothiadiazole as the core groups (electron acceptor units). The chemical structure and optical properties of the precursor were investigated by means of 1H NMR, UV–vis absorption and fluorescence spectra; the corresponding mono-nitrated polymer films were obtained in CH2Cl2-Bu4NPF6 system by electrochemical deposition method. The optical band gap of di-nitrated polymer precursor is obviously larger than the corresponding mono-nitrated polymer precursor (both ultraviolet and fluorescence spectra are obviously blue-shifted), accompanied with the obvious increased initial oxidation potential. Due to the fluorescence quenching effect of -NO2 group, their absolute quantum yields are all very low (0.0006–0.015). The spectroelectrochemistry and electrochromic kinetics of mono-nitrated polymer films (P(Th-NO2-BT) and P(EDOT-NO2-BT)) were studied. It was found that P(EDOT-NO2-BT) can show better electrochromic performance than P(Th-NO2-BT), with dark green in the neutral state and more obvious electrochromic performance in the near-infrared region (optical contrast: 38.4 %, coloration efficiency: 129.1 cm2/C, and fast response time: 1.4 s). This systematically study about the effects of nitro substitution effect on the properties of D-A electrochromic polymers, which will further expand the selection of the new acceptor units and the application prospect of nitrated electrochromic materials.

Multiple Chirality Switching of a Dye-Grafted Helical Polymer Film Driven by Acid & Base.

A stimuli-responsive multiple chirality switching material, which can regulate opposed chiral absorption characteristics, has great application value in the fields of optical modulation, information storage and encryption, etc. However, due to the rareness of effective functional systems and the complexity of material structures, developing this type of material remains an insurmountable challenge. Herein, a smart polymer film with multiple chirality inversion properties was fabricated efficiently based on a newly-designed acid & base-sensitive dye-grafted helical polymer. Benefited from the cooperative effects of various weak interactions (hydrogen bonds, electrostatic interaction, etc.) under the aggregated state, this polymer film exhibited a promising acid & base-driven multiple chirality inversion property containing record switchable chiral states (up to five while the solution showed three-state switching) and good reversibility. The creative exploration of such a multiple chirality switching material can not only promote the application progress of current chiroptical regulation technology, but also provide a significant guidance for the design and synthesis of future smart chiroptical switching materials and devices.

Bending motion induced by near-infrared laser irradiation of polymer films made by UV-curable liquid crystalline monomer containing gold-coated fine particles

Polymer films made by UV-curable liquid crystalline (LC) monomer have both characters of the external stimulus responsiveness of LC and flexibility of polymer chains. Therefore, polymer film made by UV-curable LC monomer are expected as soft actuators. By incorporating photothermal conversion materials in polymer film, the macro shape of film can be controlled by light irradiation. In this study, a polymer film made by UV-curable LC monomer containing gold-coated fine particles was prepared and its bending motion induced by near-infrared laser irradiation was studied. When the film is irradiated with near-infrared laser, it bends. We also investigated the dependence of the concentration and distribution of gold-coated fine particles in the film, and irradiation time and intensity for the bending displacement.