Transparent Polymer Films Research Articles

A novel synthesis of light transmission from upcycled polyethylene terephthalate polymer and low-density polyethylene for greenhouse design in tropical climate

Abstract To support the circular economy in Thai’s agriculture, the main interviewed challenges point to knowledge and knowhow for greenhouse structure and system boosting up productivities. One popular material that possibly affected productivity is transparent polymer film, which can be recycled based on material property and blowing machine condition. This paper investigates the light transmittance performance of transparent polyethylene terephthalate polymer (PET) and low-density polyethylene (LDPE) sheets for use in low-energy greenhouses in tropical climates. The aim of the study is to optimize the thermal performance and light transmittance of these materials to support plant growth and human comfort. The study focuses on seven stages of plant growth, each of which requires different light characteristics including 1) seed, 2) germinating, 3) young seedling, 4) older vine, 5) flowering, 6) fruit bearing and 7) harvesting and drying. Each stage requires different light characteristics, e.g. light intensity, red light, blue light, white light and ultraviolet (UV) and pulsed light (PL). The methodology involves selecting PET and LDPE materials, preparing samples for thermal property and lighting laboratory tests and analysing the results based on suitable criteria. The findings show that LDPE sheets have 28.78% lower light transmittance than PET sheets, making them suitable for supporting the seedling stage and older vines of plant growth. PET sheets, on the other hand, deliver a high intensity of red light, making them suitable for stimulating photosynthesis in older vines and during the harvesting process. The study highlights the importance of considering both thermal performance and light transmittance when selecting materials for low-energy greenhouses in tropical climates.

Facile synthesis of soluble, self-crosslinkable and crystalline polyimides with ultrahigh thermal/chemical resistance

Low-cost and processable polyimides with ultrahigh thermal/chemical stability is urgently demanded in microelectronic and aeronautics/astronautics industries. In this work, crystalline polyimides containing reactive cyano groups were synthesized from readily available monomers by facile one-step solution polycondensation method. The obtained polyimides are soluble at room temperature in the common solvents, and can be easily made into transparent polymer films. After curing, the resultant products become completely insoluble in any solvents, exhibiting excellent chemical stability. The glass transition temperature (Tg) and 5% thermal decomposition temperature (T5) for the cured polyimides are as high as 462 °C and 570 °C, respectively. The ultrahigh Tg and T5 together with good solubility are superior to most polyimides already reported in the literature. Moreover, the polyimide films are quite tough with the tensile strengths of 94–118 MPa, Young's moduli of 2.3–2.7 GPa and elongations at break of 5.3%–8.6%. The combination of facile synthesis method, solution-proccesability, excellent thermal/chemical resistance and mechanical property endows the polymers with promising applications in polymer films and composite materials.

A polymer electrolyte for rechargeable chloride ion batteries

• A poly(diallyl dimethyl ammonium chloride) (PDDAC) is proposed as an new electrolyte for chloride ion batteries. • The chloride ion conductivity is significantly varied by PEG plasticizer. • Chloride ion conductivity of 2.63 × 10 −5 S cm −1 is obtained at 303 K. • The chloride ion conducting capability is evidenced in a chloride ion battery. Chloride-ion batteries (CIBs) based on shuttling of chloride ion have recently attracted attention because of the safety, abundant resources, and high theoretical energy density. Herein, a polymer of poly(diallyl dimethyl ammonium chloride) (PDDAC) plasticized by poly(ethylene glycol) (PEG) is proposed as an new electrolyte for chloride ion batteries. The ionic conductivity of polymer electrolyte is significantly varied by the amount of plasticizer. A flexible, transparent polymer film with 70 wt% of PEG (Mw = 300) shows the highest chloride ion conductivity (2.63 × 10 −5 S cm −1 ) at 303 K. The chloride ion conducting capability is also evidenced in a lithium free chloride ion battery with CuCl as a cathode and Mg as an anode.

Effective Blue Light-Absorbing AuAg Nanoparticles in InP Quantum Dots-Based Color Conversion.

In typical color-by-blue mode-based quantum dot (QD) display devices, only part of the blue excitation light is absorbed by QD emitters, thus it is accompanied by the leakage of blue light through the devices. To address this issue, we offer, for the first time, the applicability of AuAg alloy nanoparticles (NPs) as effective blue light absorbers in InP QD-based color-by-blue platforms. For this, high-quality fluorescent green and red InP QDs with a double shell scheme of ZnSe/ZnS were synthesized and embedded in a transparent polymer film. Separately, a series of Au/Ag ratio-varied AuAg NPs with tunable plasmonic absorption peaks were synthesized. Among them, AuAg NPs possessing the most appropriate absorption peak with respect to spectral overlap with blue emission are chosen for the subsequent preparation of AuAg NP polymeric films with varied NP concentrations. A stack of AuAg NP polymeric film on top of InP QD film is then placed remotely on a blue light-emitting diode, successfully resulting in systematically progressive suppression of blue light leakage with increasing AuAg NP concentration. Furthermore, the beneficial function of the AuAg NP polymeric overlayer in mitigating undesirable QD excitation upon exposure to ambient lights was further examined.

Molecular necklace strategy for enhancing modulus and toughness of colorless transparent polyimides for cover window application

The burgeoning of flexible displays has spawned an urgent need for next-generation cover window materials, which need to combine high modulus, toughness, and ultra-high transmittance. Here, inspired by Velcro® closure, a colorless transparent supramolecular polyimide composite (CPI–C) has been prepared by self-assembly of a crown ether, 18CE6, with a diamine monomer, followed by in situ polymerization with a dianhydride monomer. In the supramolecular composite, the 18CE6 macrocycles were threaded by the CPI chain and fixed on the amide structural unit by hydrogen bonds. Numerous necklace-like molecular chains were mutually entangled to form a Velcro®-like aggregate. Due to strong interactions between the chains imparted by the interlocking rings, they were prevented from sliding under an external force. Our experimental results demonstrated that the unique supramolecular composite improved both the mechanical strength and toughness of the PI film without sacrificing its optical properties. The obtained CPIs showed good optical transmittance (86% at 450 nm), an extremely high Young's modulus (8.3 GPa), and a high elongation at break (23.8%). The described approach may provide guidance for fabricating high strength and high toughness colorless transparent polymer films for flexible cover windows. • Colorless transparent supramolecular composite film of 18CE6/polyimide was prepared. • Composite mechanism of the polyimide and 18CE6 was discussed based on H 1 NMR spectra. • Interlock chain structure improved the mechanical properties of the polyimide without sacrificing its transmittance. • Colorless transparent supramolecular composite film is potential as cover window of flexible displays.

Drum Tower‐Inspired Kirigami Structures for Rapid Fabrication of Multifunctional Shape‐Memory Smart Devices with Complex and Rigid 3D Geometry in a Two‐Stage Photopolymer

AbstractMechanically robust shape‐morphing materials that can transform from miniaturization into complex structures are highly desirable for real‐world device applications. However, fabricating mechanically robust yet geometrically complex 3D shape‐morphing structures with excellent functionality and high load‐bearing capacity remains a challenge. Inspired by drum tower buildings, a simple, rapid, and universal method is presented for fabricating multifunctional shape‐memory smart devices with complex and rigid 3D kirigami geometry in the two‐stage epoxy‐amine‐acrylate photopolymer systems. In the first‐stage reaction, transparent polymer films with a Tg of 29–49 °C are obtained by the epoxy‐amine chemistry. The shape‐memory programming process allows the first‐stage film with a drum tower‐inspired 2D kirigami pattern to be manipulated into an unsupported 3D structure. In the second‐stage reaction, UV‐induced free‐radical polymerization of methacrylate groups in the first‐stage network is employed to rapidly lock the programmed 3D kirigami structure with a Tg of 66–138 °C. The drum tower‐inspired 3D kirigami structure withstands 1000 times its own weight. The shape memory fluorescent 3D device and shape memory electronic 3D device are engineered by combining the two‐stage photopolymer system and a 3D kirigami structure. This work represents a versatile method to create multifunctional shape‐memory devices with rigid 3D geometry for potential applications.

Quantitative measurement of birefringence in transparent films across the visible spectrum

Common transparent polymer films, such as cellophane and household tape, are frequently used as examples of birefringent materials in textbooks and classroom demonstrations. Qualitatively, birefringence is often demonstrated by layering such films between crossed-polarizers. In this work, we describe an inexpensive experimental setup for the quantitative measurement of birefringence in common household films, suitable for senior high school or undergraduate labs. Whereas traditional approaches for polarization-based classroom experiments typically use monochromatic laser light, we encourage the combined use of an incoherent incandescent light source and a portable spectrometer. In addition, we demonstrate how any concomitant thin-film interference effects can be used to separately measure the optical thickness in the most heterogeneous and uniform films. Such measurement can then be used as an independent experimental confirmation of either the film's index of refraction or its thickness, given knowledge of the other. In an effort to provide examples for the data analysis procedures as well as to investigate a range of materials, we measure the birefringence across the visible spectrum of six common household polymer films, including thin kitchen wrap, cellophane, gift basket film, and common adhesive tapes.

(Digital Presentation) Monitoring and Controlling Tautomerization in Phthalocyanines, Porphyrines and Porphycenes By Optical Single-Molecule Imaging and Spectroscopy

Tautomerization is an intramolecular chemical reaction defined as structural interconversion of a molecule between two isomers separated by a low energy barrier. Tautomerization in free base phthalocyanines, porphyrins or porphycenes has fascinated and attracted chemists and physicists alike over the last decades for its fundamental importance in various chemical and biological systems and many applications in technology [1,2]. Particularly interesting is the reaction rate which can range over orders of magnitude depending on the temperature and the local environment. In solution, this reaction in porphycenes occurs usually in several picoseconds or even faster, as determined via anisotropy studies by ultrafast transient absorption spectroscopy [3] and in porphyrins at cryogenic temperatures it can last for hours or days as determined form the live time of narrow spectral holes photochemically burned in the inhomogeneously broadened absorption band with a narrow band laser [4]. However, a spectacular and unexpected observation has been made by optical single molecule imaging and spectroscopy [5]. Examining a large number of single molecules embedded at low concentration in various polymer matrices at room temperature has revealed unquestionably that the rate in these molecules can vary dramatically over time such that tautomerization can be frozen for seconds and longer under ambient conditions[6]. The interconversion of the inner protons of phthalocyanine changes the orientation of the transition dipole moment by 90o degrees with respect to the molecular structure. Hence, if these molecules are embedded with a fixed orientation in a transparent solid polymer film at high dilution and tautomerization is frozen, the orientation of their transition dipole moments can be determined by polarization spectroscopy.Here we report on our recent experimental and theoretical studies of monitoring tautomerization by fluorescence imaging of single molecules of phthalocyanines, porphyrins, or porphycenes excited in the tightly focused azimuthally and radially polarized laser beam with a sample scanning confocal optical microscope equipped with single photon counting electronics and a fluorescence spectrometer. This technique has been used to determine the transition dipole moment orientation of single molecules, the polarizability of plasmonic nanoparticles or the dimensionality of single quantum dots. Different diffraction limited fluorescence intensity patterns are observed for molecules that undergo tautomerization and for those that do not. The latter corresponds to a molecule with a fixed transition dipole moment direction, whereas the tautomerizing molecule can be treated as the superposition of two emitters with different transition dipole moment orientations.Previous studies have shown that tautomerization in porphyrins or phthalocyanines can occur via ground state tunneling and is frozen at low temperatures, particularly at cryogenic temperatures. The structural heterogeneity in a polymer matrix leads to a distribution of asymmetrically distorted ground state double well potential and hence can lead to long residence times in the deeper energy minimum. However, even at helium temperatures tautomerization can be induced by electronic excitation to the first excited state, making photochemical spectral hole-burning possible. Recently we could demonstrate in a single-molecule study that the tautomerization rate of phthalocyanine tetrasulfonate embedded in a thin PVA-film at room temperature could be controlled in a tunable λ/2 Fabry Perot resonator by weak coupling between the electronically excited state and the vacuum electromagnetic field of a resonant cavity mode.

Transparent and fluorescent breath figure arrays prepared from end-functionalized copolymers

Fluorescent and transparent polymer films with exquisite micro-structures are ideal candidates for anti-counterfeiting tags. However, it is still a great challenge to embed such properties in one breath figure array due to the restriction of the film-forming ability of polymers. In this work, we designed and synthesized fluorescent copolymers from styrene and 1-pyrenylmethyl methacrylate (PYMMA) and studied their self-assembly behaviors via the breath figure method. The significance of end groups and topologies have been investigated in detail. Novel hexagonal breath figure arrays with high transparency are formed at extremely low concentration (down to 0.06 mg/mL). The breath figure arrays display blue honeycomb pattern when irradiated by ultraviolet light. Breath figure arrays with such special optical properties demonstrated an ideal solution for anti-counterfeiting tags. Besides, this work demonstrates the significance of polymer architecture on the morphology of breath figure arrays and may enlighten the polymer design for a broad range of applications. • Fluorescent copolymers were designed and synthesized for self-assembly by the breath figure method. • A highly regular breath figure array can be formed at polymer concentration of as low as 0.06 mg/mL. • Transparent and fluorescent breath figure arrays are potential for anti-counterfeiting. • Effects of end groups and topologies of polymers on the morphology of breath figure arrays were studied.

Organic-Inorganic Hybrid Flower-Shaped Microspheres Applied in Photoelectrochemical Sensing.

Organic-inorganic hybrid materials are rarely applied in photoelectrochemical (PEC) sensing because of the serious charge-carrier recombination in organic conjugated polymers. In this work, a series of poly(3,4-ethylenedioxythiophene) (PEDOT)/ZnIn2S4 hybrid flower-shaped microspheres were synthesized using ionic liquids (ILs) as the supporting electrolyte for EDOT electropolymerization and as the regulating reagent for controlling ZnIn2S4 growth, respectively. It was found that the hybrid material [HOEMIM]NTf2-PEDOT/[HOEMIM]BF4-ZnIn2S4 ([HOEMIM]+: 1-hydroxyethyl-3-methylimidazolium cation; NTf2-: bis(trifluoromethanesulfonyl)amide) was the optimal one, with a smooth, transparent, and continuous polymer film covering the uniform and ordered cross-linked nanosheet arrays. The hybrid material could produce a high anodic photocurrent, which was about 78 times as high as that produced by the [HOEMIM]BF4-ZnIn2S4. The enhancement effect should be the highest among all the organic-inorganic hybrid materials reported so far. This was related to its unique micromorphology structure, p-n heterojunction, and the coexisting ILs, which restrained the charge-carrier recombination in PEDOT and enhanced PEDOT sensitization to ZnIn2S4. Then, a carcinoembryonic antigen PEC immunosensor was constructed based on the photoanodic sensing platform, and it exhibited good performance. Furthermore, the [HOEMIM]BF4-ZnIn2S4 was treated with NaClO solution to create the [HOEMIM]NTf2-PEDOT/[HOEMIM]BF4-S-ZnwInxSyOz general platform for both photoanodic and photocathodic sensing. As a proof of concept, L-cysteine and dissolved oxygen were used as models for photoanodic and photocathodic sensing, respectively. The results demonstrated that the general PEC platform was quite competent. This work opens up a window for the design of organic-inorganic hybrid PEC materials and will promote the application of such hybrid materials in PEC biosensing.

Enhancement of Ultraviolet Light Resistance of Colorless and Transparent Semi-Alicyclic Polyimide Nanocomposite Films via the Incorporation of Hindered Amine Light Stabilizers for Potential Applications in Flexible Optoelectronics.

Optically transparent polymer films with excellent thermal and ultraviolet (UV) resistance have been highly desired in advanced optoelectronic fields, such as flexible substrates for photovoltaic devices. Colorless and transparent polyimide (CPI) films simultaneously possess the good thermal stability and optical transparency. However, conventional CPI films usually suffered from the UV exposure and have to face the deterioration of optical properties during the long-term service in UV environments. In the current work, the commercially available hindered amine light stabilizers (HALS) were tried to be incorporated into the semi-alicyclic CPI matrix with the aim of enhancing the UV exposure stability. For this target, a CPI-0 film was first prepared from hydrogenated pyromellitic dianhydride (HPMDA) and 2,2′-dimethylbenzidine (DMBZ) via a one-step polycondensation procedure. Then, the commercially available HALS were incorporated into the CPI-0 (HPMDA-DMBZ) film matrix to afford four series of CPI/HALS composite films. Experimental results indicated that the Tinuvin® 791 HALS showed the best miscibility with the CPI-0 film matrix and the derived CPI-D series of composite films exhibited the best optical transmittances. The CPI-D nanocomposite films showed apparently enhanced UV exposure stability via incorporation of the 791 additives. For the pristine CPI-0 film, after the UV exposure for 6 h, the optical properties, including the transmittance at the wavelength of 350 nm (T350), lightness (L*), yellow indices (b*), and haze obviously deteriorated with the T350 values from 55.7% to 17.5%, the L* values from 95.12 to 91.38, the b* values from 3.38 to 21.95, and the haze values from 1.46% to 9.33%. However, for the CPI-D-10 film (791: CPI-0 = 1.0 wt%, weight percent), the optical parameters were highly maintained with the T350 values from 61.4% to 53.8%, the L* values from 95.46 to 95.36, the b* values from 1.84 to 1.51, and the haze values from 0.69% to 3.34% under the same UV aging conditions.

Organic solvent assisted laser processing of transparent polymer films based on the swelling and penetration behavior

The laser processing of polymer films has significant importance due to the wide applications in various fields. The problems in laser processing of transparent polymer films caused by the poor absorption and current doping methods have prevailed. In this paper, a simple, efficient, and low-cost doping and laser processing method based on polymers’ swelling and penetration behavior was applied to improve the laser processing of transparent polymer films: organic solvent assisted laser processing (SALP). In the SALP method, various common organic solvent molecules (Ethanol, Acetone, N, N-dimethylformamide, Chloroform) were introduced into transparent polydimethylsiloxane (PDMS) films through the swelling and penetration (SP) pretreatment and acted as the dopant to improve the efficiency, capability, and quality of laser processing. Experimental results showed that the SALP method performed higher efficiency and capability (kerf depth: 296.79 ± 11.98 μm, kerf width: 16.59 ± 1.46 μm, kerf aspect ratio: 18.02 ± 1.98) under the same processing conditions compared to the typical laser processing (TLP) method (kerf depth: 137.36 ± 6.47 μm, kerf width: 27.30 ± 1.11 μm, kerf aspect ratio: 5.04 ± 0.31). The roughness of the kerf inner surface and the debris and microcracks on the kerf surface were also significantly reduced. More importantly, this method hardly influenced the original properties of the native polymer films due to the removability of organic solvents. On the one hand, the introduction of organic solvent molecules improved the optical absorption of PDMS films and the heat transfer during laser processing. On the other hand, the excitation, ionization, and dissociation of organic solvent molecules under laser irradiation improved the decomposition process of PDMS, which improved photochemical reaction and promoted the complete and uniform decomposition in laser processing. The SALP method has enlightening significance for improving the laser processing of polymers and investigating the laser ablation mechanism.

Two states of a light-sensitive membrane protein captured at room temperature using thin-film sample mounts.

Room-temperature diffraction methods are highly desirable for dynamic studies of biological macromolecules, since they allow high-resolution structural data to be collected as proteins undergo conformational changes. For crystals grown in lipidic cubic phase (LCP), an extruder is commonly used to pass a stream of microcrystals through the X-ray beam; however, the sample quantities required for this method may be difficult to produce for many membrane proteins. A more sample-efficient environment was created using two layers of low X-ray transmittance polymer films to mount crystals of the archaerhodopsin-3 (AR3) photoreceptor and room-temperature diffraction data were acquired. By using transparent and opaque polymer films, two structures, one corresponding to the desensitized, dark-adapted (DA) state and the other to the ground or light-adapted (LA) state, were solved to better than 1.9 Å resolution. All of the key structural features of AR3 were resolved, including the retinal chromophore, which is present as the 13-cis isomer in the DA state and as the all-trans isomer in the LA state. The film-sandwich sample environment enables diffraction data to be recorded at room temperature in both illuminated and dark conditions, which more closely approximate those in vivo. This simple approach is applicable to a wide range of membrane proteins crystallized in LCP and light-sensitive samples in general at synchrotron and laboratory X-ray sources.

Ultra-low-cost, flexible and durable electrochromic tape device based on aluminum foil

Electrochromic devices (ECDs) have the ability to selectively change their color state. They come in many forms, such as smart windows, e-ink displays and recently even as flexible tapes. Since most of ECDs incorporate traditional “sandwich” architecture, which requires at least one electrode to be made of a transparent conductive polymer or thin film ceramics, they are considered too expensive and fragile compared to devices made from metal or alloy foils. For the first time, we present a true low-cost, flexible and durable ECD tape that uses a common “kitchen-grade” aluminum foil for electrodes, while employing a Li-WO3 intercalation based electrochromic system. The presented ECD tape is capable of showing two color states. The tested tapes were up to 20 cm long but could be easily made longer due to their “inverted sandwich” architecture. Due to the absence of transparent counter electrode, the assembled ECD tape has excellent durability properties and could be used in color changing clothes, adaptive camouflage or other applications.

Temperature Field-Assisted Ultraviolet Nanosecond Pulse Laser Processing of Polyethylene Terephthalate (PET) Film.

Understanding the mechanism of and how to improve the laser processing of polymer films have been important issues since the advent of the procedure. Due to the important role of a photothermal mechanism in the laser ablation of polymer films, especially in transparent polymer films, it is both important and effective to adjust the evolution of heat and temperature in time and space during laser processing by simply adjusting the ambient environment so as to improve and understand the mechanism of this procedure. In this work, studies on the pyrolysis of PET film and on temperature field-assisted ultraviolet nanosecond (UV-ns) pulse laser processing of polyethylene terephthalate (PET) film were performed to investigate the photothermal ablation mechanism and the effects of temperature on laser processing. The results showed that the UV-ns laser processing of PET film was dominated by the photothermal process, in which PET polymer chains decomposed, melted, recomposed and reacted with the ambient gases. The ambient temperature changed the heat transfer and temperature distribution in the laser processing. Low ambient temperature reduced the thermal effect and an increase in ambient temperature improved its efficiency (kerf width: 39.63 μm at −25 °C; 48.30 μm at 0 °C; 45.81 μm at 25 °C; 100.70 μm at 100 °C) but exacerbated the thermal effect.

Investigation of the phase delay of radiation by a transparent ferroelectric polymer film

In this paper, we study samples of an optically transparent ferroelectric polymer film with deposited nanoscale electrically conductive coatings designed to modulate the transmitted electromagnetic radiation of the visible and near-infrared wavelengths. Such films can be used, for example, in interference devices for phase delay compensation or for the implementation of the Phase Shifting Interferometry, in adaptive optics, etc. To measure the phase delay of the radiation passing through the samples under study, an installation based on the Mach-Zehnder interferometer was used. In the illumination branch of the installation, a broadband radiation source and an acousto-optic tunable filter are installed; in one of the arms of the interferometer, the test sample is installed. The interference pattern was recorded on a matrix radiation receiver; the phase information was decoded by digital holography methods. The report presents the results of measurements and shows that a modulation of the passed optical radiation occurs under the influence of the electric field as a result of changes in the geometrical dimensions of the film.

Quasi-Isotropically Thermal Conductive, Highly Transparent, Insulating and Super-Flexible Polymer Films Achieved by Cross Linked 2D Hexagonal Boron Nitride Nanosheets.

Polymer-based thermal management materials (TIMs) show great potentials as TIMs due to their excellent properties, such as high insulation, easy processing, and good flexibility. However, the limited thermal conductivity seriously hinders their practical applications in high heat generation devices. Herein, highly transparent, insulating, and super-flexible cellulose reinforced polyvinyl alcohol/nylon12 modified hexagonal boron nitride nanosheet (PVA/(CNC/PA-BNNS)) films with quasi-isotropic thermal conductivity are successfully fabricated through a vacuum filtration and subsequent self-assembly process. A special structure composed of horizontal stacked hexagonal boron nitride nanosheets (h-BNNSs) connected by their warping edges in longitudinal direction, which is strengthened by cellulose nanocrystals, is formed in PVA matrix during self-assembly process. This special structure makes the PVA/(CNC/PA-BNNS) films show excellent thermal conductivity with an in-plane thermal conductivity of 14.21 W m-1 K-1 and a through-plane thermal conductivity of 7.29 W m-1 K-1 . Additionally, the thermal conductive anisotropic constants of the as-obtained PVA/(CNC/PA-BNNS) films are in the range of 1 to 4 when the h-BNNS contents change from 0 to 60wt%, exhibiting quasi-isotropic thermal conductivity. More importantly, the PVA/(CNC/PA-BNNS) films exhibit excellent transparency, super flexibility, outstanding mechanical strength, and electric insulation, making them very promising as TIMs for highly efficient heat dissipation of diverse electronic devices.

Unveiling electron transfer in a supramolecular aggregate for adaptive and autonomous photochromic response

SummaryInteractive and responsive materials are dynamic molecular systems that are capable of modulating their behavior and adapting to environment autonomously. Photochromic materials are among the fascinating class of dynamic responsive systems and widely used in molecular switches and optoelectronic devices. However, the phototriggered color changing largely relies on the conformation transformation of the photochromic motif, which significantly limited their usage in organic liquid solutions. Herein, we demonstrate a photochromic organic supramolecular system by using electron-rich N,N-dimethylacetamide (DMA) and electron-deficient naphthalenediimide (NDI) as a donor and acceptor, respectively. In the binary system, the photo-induced electron transfer through lone pair···π interactions pathway leads to dynamic photochromic response not only in the solution but also in the crystalline aggregated state. Furthermore, by incorporating the supramolecules in the polymer matrix, the transparent polymeric film also exhibits rapid photochromic response, which makes it a promisingly interactive and adaptive photochromic material.

Colourless luminescent solar concentrators based on Iridium(III)-Phosphors

The first real examples of luminescent solar concentrators (LSCs) based on Ir(III) cyclometalates, are described herein. Two new Ir(III) tetrazole complexes, namely [Ir(ppy)2(iQTZ-PPG)]+ and [Ir(npy)2(iQTZ-PPG)]+, where (C^N) = ppy, 2 phenylpyridine or npy = 2-(naphthalen-2-yl)pyridine and iQTZ-PPG = 1-(2-(prop-2-yn-1-yl)-2H-tetrazol-5-yl)isoquinoline, were synthesized, fully characterized and tested as phosphors for colourless LSCs. Notably, increasing quantities (0.2–1.8 wt %) of the new Ir(III) based phosphors were dispersed in different acrylate polymers like poly(methyl methacrylate), PMMA, poly(benzyl methacrylate), PBzMA and poly(cyclohexyl methacrylate), PCHMA, leading to visible transparent polymeric films exhibiting excellent photostability and bright yellow to orange phosphorescent emissions. The performances as solar collectors of all the Ir(III)-doped polymers were investigated, providing results comparable, or superior, to those obtained from colourless LSC based on organic fluorophores. In fact, the best optical efficiency (ηopt up to 7%, combined to transmittance close to 80% at 390 nm) was displayed by the polymer film obtained from physical dispersion of [Ir(ppy)2(iQTZ-PPG)]+ (1.4 wt %) in PCHMA.

A highly reliable contact-separation based triboelectric nanogenerator for scavenging bio-mechanical energy and self-powered electronics

The increasing interest in harvesting mechanical energy from day-to-day activities is gaining huge interest among researchers. We have fabricated a triboelectric nanogenerator (TENG) made of aluminum and PDMS film acting as positive and negative triboelectric layers. The layers are arranged in an arc-shaped structure with an air gap of 1 cm between the layers of the device. The PDMS layer is made by blending the polymer solution with the hardener in an appropriate ratio and dried to make the transparent and flexible polymer film. The device shows a maximum electrical response of 110 V and 260 nA voltage and current with the power density of 2.9 mW/m2 at 100 MΩ load resistance. Further, the device has been used for lighting green LEDs and charging commercial capacitors. An Arduino board was connected with LED and buzzer, which was triggered by the TENG device. This shows that with the proper usage of electronic components TENG can be used for self-powered sensors and with IoT applications.