Chromatic Transitions Research Articles

A writable aniline‐functionalized polydiacetylene composite with obvious colorimetric change upon both heating and near infrared lights irradiation

AbstractDue to the unique optical and chromatic properties toward various external stimuli, conjugated polydiacetylene (PDA) materials are attracting a great attention from scientists. And the fabrication of PDA embedded composites would further expand the application prospect. In this work, aniline substituted diacetylene derivative was embedded into wax matrix to form a writable composite. After UV induced 1,4‐topochemical polymerization, the patterns generated from the PDA/wax composite showed clearly a blue‐to‐purple‐to‐red colorimetric change upon thermal stimulus. More interestingly, with the introduction of two representative near‐infrared (NIR) dyes to the composite, the PDA also showed blue‐to‐red chromatic transition in response to distinctive NIR lights irradiation.

Flexible, Programmable, Chiroptical Polymer Films of Twisted Stacking Layers for Circular Polarization‐Based Multiplex Color Display

AbstractFlexible films with strong and tunable chiroptical responses are highly desirable and potentially applicable in 3D display, wearable, and implantable devices, etc. Traditional organic or polymer‐based materials typically exhibit weak chiroptical response. Recently, strong chiroptical properties are reported for some chiral inorganic nanostructures and metasurfaces; however, the difficulties to fabricate and control chiroptical properties in a feasible and economical fashion on deformable substrate limit their practical applications. Herein, a simple and cost‐effective method is reported to fabricate flexible chiroptical polymeric films with giant optical activity (gabs > 0.5) via aligning two anisotropic polydiacetylene (PDA) layers in a twisted fashion. The chromatic transition of PDA is exploited to prepare films with either photonic homostructures or heterostructures to extend spectral range, each featuring distinct frequency dependence and adjustable optical activity. This allows to demonstrate a full color, high brightness, fast responsive, multiplex laser display based on circular polarization. The large chiroptical response of such films, combined with the tunability, flexibility, and compatibility with various substrate choices are also exploited in other applications such as circular polarized luminescence and optical encryption.

Near‐Infrared Light/Thermal Dual‐Responsive Epoxy‐Based Polydiacetylene Composite for 3D Printing

AbstractPolydiacetylene (PDA) is a promising material due to the chromatic transition through external stimulus. However, near‐infrared (NIR) light is on the periphery of attention to achieve the colorimetric change. Herein, an epoxy‐based PDA composite is prepared through a dual‐wavelength orthogonal photopolymerization strategy where 405 nm light and UV light are utilized in turn. The appearance of blue phase indicates that ene–yne‐conjugated PDA backbone is successfully formed in the composite. The generated PDA composite exhibits a blue‐to‐red color change upon heating. More interestingly, the fast chromatic transition is also observed under a laser diode at 1064 nm irradiation in the presence of a NIR dye (IR 1064). And such NIR light responsiveness of the composite upon NIR light irradiation is demonstrated by thermal imaging camera. Finally, the 3D printing technique is applied to the composite and the fabricated 3D pattern exhibits dual colorimetric transition in response to both heat and NIR light stimuli. Therefore, the newly proposed approach finds great applications in functional materials due to the unique dual thermal or NIR light stimuli responsiveness.

Controllable color change of polydiacetylene vesicles under thermal-photo stimuli

Polydiacetylene (PDA) is an attractive material due to its unique chromatic transition properties by external stimuli. Its blue-to-red color transitions observed by the naked eye make the PDA a promising optical biosensor. However, the chromatic transitions of most PDA materials are irreversible, leading to restricted applications of PDA-based biosensors. In this study, we suggest that the colorimetric reversibility of PDA by the thermal-photo stimuli cycles is closely related to the difference in hydrogen bond strength and ionic interactions between adjacent headgroups of PDA vesicles. By fabricating three types of PDA vesicles consisting of single or complex headgroups, their reversibility in color change was compared. The PDA vesicles composed of both carboxyl- and amine-terminated monomers (poly(PCDA/PCDA-EDA)) at a molar ratio of 1:1 exhibited noticeable chromatic reversibility with colorimetric response (CR) values of 84–91% and 24–61% during heating and UV irradiation cycles, respectively. And, the reversibility of the poly(PCDA/PCDA-EDA) vesicles under different pH conditions was examined to assess the effect of ionic interactions. To investigate the changes in the backbone and strength of hydrogen bonds in the prepared PDA vesicles, Raman and Fourier transform infrared (FT-IR) spectroscopies were executed, respectively. These results demonstrate that the hydrogen bond strength and ionic interactions of PDA vesicles with different terminal functional groups plays an important role in “red to blue” backward transitions, which can ultimately be applied to the development of recyclable PDA materials.

High-performance all-inorganic portable electrochromic Li-ion hybrid supercapacitors toward safe and smart energy storage

Li-ion hybrid supercapacitors (LHSs) bridged the gap between batteries and supercapacitors, and simultaneously attracted tremendous attention because of their potential applications in intelligent portable electronic devices. Nevertheless, obtaining all-inorganic LHSs with excellent environmental compatibility and smart display features remains a remarkable challenge. Herein, we designed and constructed a novel ultrathin all-inorganic electrochromic Li-ion hybrid supercapacitor (ELHS) by incorporating battery-type (LiMn2O4) and supercapacitor-type (WO3) electrochromic materials into one cell. The resultant ELHS achieved stable and reversible chromatic transitions during the electrochemical process, providing sufficient real-time information on the working status. Benefiting from the matching potential windows of the individual active electrodes and the all-inorganic construction of the whole device, the optimized ELHS exhibited an extended working voltage of 2.5 V. Impressively, the ELHS demonstrated an ultrahigh volumetric energy/power density (16.2 W cm−3/0.21 Wh cm−3) and remarkable cycling stability with ~95.4% capacitance retention after 5000 cycles. The observed performance characteristics outperformed most previously reported electrochromic energy storage devices and were comparable to some commercial devices. Significantly, inorganic electrolytes were introduced into the ELHS, which endowed it with outstanding environmental adaptability and ability to work at progressively varying temperatures (0–75 °C). We envision that this work may open new avenues for the development of next-generation safe and portable hybrid energy storage devices.

A polydiacetylene-based colorimetric sensor as an active use-by date indicator for milk

Current food date marking tools fail to take into account variables that impact shelf life, leading to food waste and posing human health risks. Herein, we develop a polydiacetylene/zinc oxide (PDA/ZnO) colorimetric sensor that can indicate milk freshness in real time. The PDA/ZnO system is engineered to indicate the freshness of full cream milk by monitoring its pH based on lactic acid concentration, an indicator of bacterial spoilage. The sensitivity is tuned by selection of the diacetylene monomers from which it is composed. Designs constructed from shorter chain diacetylenes are found to undergo chromatic transitions at a lower lactic acid concentration. Two new methods to tune PDA/ZnO sensitivity to lactic acid are explored, including relocation of the diacetylene functional group and lipid doping. A system constructed from 5,7-hexadecadiynoic acid (HDDA) and ZnO can discriminate between fresh (pH 6.8–6.0), spoiling (pH 6.0–4.5), and spoiled milk (pH 4.5–4.0) by a respective blue to purple to red color change. The chromatic stability of the PDA/ZnO sensor in food is studied as previous reports have shown the system to be unstable. We present a new method that stabilizes the nanocomposite by pre-exposure to the food matrix prior to photopolymerization.

3D Printing of Polydiacetylene Photocomposite Materials: Two Wavelengths for Two Orthogonal Chemistries

Polydiacetylene (PDA) materials are appealing and gaining increasing research interest due to their outstanding chromatic transition and fluorescence enhancement effects upon exposure to various environmental stimuli. However, despite the photomask method, there are very few reports about the spatial controllable photopolymerization and subsequent 3D printing of PDA until now. Herein, for the first time, we reported the preparation of PDA photocomposite materials based on polyacrylate through the strategy of dual-wavelength polymerization and orthogonal chemistry. First, diacetylene (DA) monomers were homogeneously dispersed in acrylate resin. Then a violet light emitting diode (LED) (or laser diode) was used for the free radical polymerization of polyacrylate. Finally, UV irradiation was utilized to induce the 1,4-topopolymerization of PDA, which could show a successive blue to purple to red color transition in response to the gradient increment of temperature. Interestingly, instead of photomasks, we applied a 3D printing approach directly to this composite material and fabricated some macroscopic stereo patterns, which also illustrated thermochromic properties. This novel kind of functional photocomposite material would demonstrate a huge application prospect in many potential fields, including colorimetric sensing, information encryption, anticounterfeiting, and so on.

Integrated electrochromic supercapacitors with visual energy levels boosted by coating onto carbon nanotube conductive networks

Conductive polymer polyaniline (PANI) demonstrates potential applications in developing integrated smart energy devices based on the bi-functional electrochromic optical modulation and electrochemical energy storage. One challenge is to improve the structural stability of PANI films in response to repeating doping and dedoping of anions during the electrochemical redox process. Herein, a facile and effective approach is developed for improving the electrochemical performance of PANI by coating onto the carbon nanotube (CNT) conductive networks. The introduction of CNT firstly provides multiple directions for electron transfer and thus enhances the charge capacity of PANI. Then, the polymerization of PANI onto the CNT (PANI@CNT) contributes to the formation of a 3D network film, which effectively reduces the structural failure caused by anions intercalation and extraction. Compared with compact PANI film, a substantial promotion of bi-function achieves in the porous PANI@CNT one, whose optical transmittance modulation increases to over 40% and the specific capacitance of the initial cycle is almost tripled. On the basis of reversible and stable chromatic transitions between different charged states, the PANI@CNT electrode is further developed to be a smart electrochromic supercapacitor exhibiting visual energy storage level. We expect that this work may lead to new designs of robust smart energy storage devices.

Principles of interpreting P. Tychyna’s poetry in the vocal cycle “Enharmonic” by L. Dychko

Principles of interpreting P. Tychyna’s poetry in the vocal cycle “Enharmonic” by L. Dychko

High-temperature adaptive and robust ultra-thin inorganic all-solid-state smart electrochromic energy storage devices

Electrochromic energy storage devices (EESDs) that offer high energy and power densities are extremely desirable for use in applications ranging from civilian portable electronic devices to building windows. However, the performace of EESDs under high temperature is still a big challenge because of unavoidable performance decays and the invevitable damage of components. Herein, we demonstrate an ultra-thin inorganic all-solid-state smart EESD by incorporating two complementary electrochromic materials into the electrodes. The synergy of the inorganic layers enabled the EESD to withstand a wide temperature range (20 °C-75 °C). Impressively, the volume capacitance of the EESD increased as the temperature was increased, suggesting that the EESD possess excellent adaptability to high temperatures. More importantly, the EESD exhibited outstanding capacity retention and cycling ability when operated at progressively varied temperatures. The volume capacitance of the EESD remained at 96.2% of its initial value after 2000 cycles even at 75 °C. This performance was better than most energy storage devices at high-temperatures. Additionally, obvious chromatic transition occurred during the charge/discharge process and the maximum transmittance difference between different states of the EESD reached up to 49% at 75 °C. We envision that our research provides a novel route to realize the coincident utilization of optical-electrochemical energy.

Phase Change Ultrasound Contrast Agents with a Photopolymerized Diacetylene Shell.

Phase change contrast agents for ultrasound (US) imaging consist of nanodroplets (NDs) with a perfluorocarbon (PFC) liquid core stabilized with a lipid or a polymer shell. Liquid ↔ gas transition, occurring in the core, can be triggered by US to produce acoustically active microbubbles (MBs) in a process named acoustic droplet vaporization (ADV). MB shells containing polymerized diacetylene moiety were considered as a good trade off between the lipid MBs, showing optimal attenuation, and the polymeric ones, displaying enhanced stability. This work reports on novel perfluoropentane and perfluorobutane NDs stabilized with a monolayer of an amphiphilic fatty acid, i.e. 10,12-pentacosadiynoic acid (PCDA), cured with ultraviolet (UV) irradiation. The photopolymerization of the diacetylene groups, evidenced by the appearance of a blue color due to the conjugation of ene-yne sequences, exhibits a chromatic transition from the nonfluorescent blue color to a fluorescent red color when the NDs are heated or the pH of the suspension is basic. An estimate of the molecular weights reached by the polymerized PCDA in the shell, poly(PCDA), has been obtained using gel permeation chromatography and MALDI-TOF mass spectrometry. The poly(PCDA)/PFC NDs show good biocompatibility with fibroblast cells. ADV efficiency and acoustic properties before and after the transition were tested using a 1 MHz probe, revealing a resonance frequency between 1 and 2 MHz similar to other lipidic MBs. The surface of PCDA shelled NDs can be easily modified without influencing the stability and the acoustic performances of droplets. As a proof of concept we report on the conjugation of cyclic RGD and PEG chains of the particles to support targeting ability toward endothelial cells.

Computational elucidation of the effects induced by music making.

Music making, in the form of free improvisations, is a common technique in music therapy, used to express one’s feelings or ideas in the non-verbal language of music. In the broader sense, arts therapies, and music therapy in particular, are used to induce therapeutic and psychosocial effects, and to help mitigate symptoms in serious and chronic diseases. They are also used to empower the wellbeing and quality of life for both healthy individuals and patients. However, much research is still required to understand how music-based and arts-based approaches work, and to eventually enhance their effectivity. The clinical setting employing the arts constitutes a rich dynamic environment of occurrences that is difficult to capture, being driven by complex, simultaneous, and interwoven behavioral processes. Our computational paradigm is designed to allow substantial barriers in the arts-based fields to be overcome by enabling the rigorous and quantitative tracking, analyzing and documenting of the underlying dynamic processes. Here we expand the method for the music modality and apply it in a proof of principle experimentation to study expressive behavioral effects of diverse musical improvisation tasks on individuals and collectives. We have obtained statistically significant results that include empirical expressive patterns of feelings, as well as proficiency, gender and age behavioral differences, which point to variation factors of these categorized collectives in music making. Our results also suggest that males are more exploratory than females (e.g., they exhibit a larger range of octaves and intensity) and that the older people express musical characterized negativity more than younger ones (e.g., exhibiting larger note clusters and more chromatic transitions). We discuss implications of these findings to music therapy, such as behavioral diversity causality in treatment, as well as future scientific and clinical applications of the methodology.

Development of naphthalimide-functionalized thermochromic conjugated polydiacetylenes and their reversible green-to-red chromatic transition in the solid state

Development of PDAs has received great attention in many fields due to their optical and chromatic properties towards external stimuli. In this article, two novel PDAs (NPI-PDA1 and NPI-PDA2) containing naphthalimide as a head group are designed and synthesized through self-assembly followed by topochemical polymerization, and these compounds show a reversible green-to-red colorimetric transition upon heating. PEO-embedded films are fabricated to facilitate the investigation of the thermochromic properties, and the surface morphologies of the films are observed by SEM analysis. The thermochromic behavior and color transitions are observed using photography and electronic absorption spectroscopy. The changes in the extended ene-yne conjugated system of the polymer during heat treatment are successfully monitored by Raman spectrometry. Moreover, PDA-embedded crayon wax-based hand-writable pens are fabricated and used efficiently on a solid substrate. NPI-PDA1 and NPI-PDA2 display excellent reversibility in the temperature ranges of 25–120 °C and 25–160 °C, respectively in the PEO polymer and paraffin wax matrices.

Fabrication of colorful colloidal photonic crystal fibers via a microfluidic spinning technique

A new strategy is demonstrated to fabricate colorful colloidal photonic crystal fibers (CPCFs) by microfluidic spinning technique. We employed a homogeneous mixture of viscous polyvinylpyrrolidone (PVP) and monodisperse SiO2 particles to fabricate micro-scale fibers. By manipulating the motor speed of the microfluidic spinning machine, various diameter fibers were produced efficiently. Monodisperse SiO2 particles can assemble into photonic crystal structures by removing PVP through calcination and show bright structural colors, which can be easily adjusted by changing the sizes of SiO2 colloids. In addition, we successfully fabricated humidity-sensitive polyacrylamide (PAM)/CPCFs, which exhibited obvious color response to the environmental humidity. The chromatic transitions span over almost the whole visible spectrum. This work might promote the development of colorful colloidal photonic crystal fibers via a microfluidic spinning technique.

Chromatic transitions in the emergence of syntax networks.

The emergence of syntax during childhood is a remarkable example of how complex correlations unfold in nonlinear ways through development. In particular, rapid transitions seem to occur as children reach the age of two, which seems to separate a two-word, tree-like network of syntactic relations among words from the scale-free graphs associated with the adult, complex grammar. Here, we explore the evolution of syntax networks through language acquisition using the chromatic number, which captures the transition and provides a natural link to standard theories on syntactic structures. The data analysis is compared to a null model of network growth dynamics which is shown to display non-trivial and sensible differences. At a more general level, we observe that the chromatic classes define independent regions of the graph, and thus, can be interpreted as the footprints of incompatibility relations, somewhat as opposed to modularity considerations.

Photochromic Paper Indicators for Acidic Food Spoilage Detection.

A photoresponsive microstructured composite is fabricated through the impregnation of cellulosic filter paper (FP) with a spiropyran-modified acrylic polymer. The polymer enwraps uniformly each individual cellulose fiber, increases the thermal stability of cellulose, and ensures the preservation of the composite functionalities even upon removal of the surface layers through mechanical scratching. The photochromic spiropyran moieties of the polymer, even while embedded in the cellulosic sheet, can reversibly interconvert between the colorless spiropyran and the pink merocyanine isomeric states upon irradiation with UV and visible light, respectively. Moreover, the photochromic polymer presents a faster photochromic response and a higher resistance to photodegradation, with an outstanding reusability for more than 100 switching cycles when it is incorporated in the cellulose network. Most importantly, the acidochromism of the modified FP, attributed to the spiropyran molecules after UV activation, allows the real-time optical and visual detection of acidity changes and spoilage in food products, such as wine and milk. Spoilage due to bacterial degradation and oxidation processes generates acidic vapors that induce the protonation of the merocyanine. This results in a visually detectable chromic transition from pink to white of the treated cellulose fibers, corresponding to a blue shift in the absorption spectrum. The developed photoresponsive cellulose composite can serve as cost-effective robust optical component in integrated functional platforms and consumer-friendly indicators for smart food packaging, as well as portable on demand acidoresponsive interfaces for gas monitoring in industrial and environmental applications.

Colorimetric polydiacetylene (PDA) liposome-based assay for rapid and simple detection of GST-fusion protein

The detection of proteins by gel electrophoresis and subsequent staining is the most commonly used method for protein analysis, but it requires considerable time and effort as well as denatured protein samples. In this study, we developed a polydiacetylene (PDA)-based colorimetric sensor that does not require any instrument, time-consuming processes, or protein denaturation steps. Specifically, to assess the expression of glutathione S-transferase (GST)-fusion recombinant protein utilizing the interactions between the enzyme GST and its substrate, glutathione (GSH), a terminal group of PDA monomers was modified with the GSH tripeptide. The diacetylene liposome containing the GSH-modified diacetylene monomer was polymerized upon UV irradiation at 254 nm, resulting in a blue PDA liposome. The terminal GSH moiety of the PDA liposome seemed to be perpendicular to the PDA backbone, enabling its easy interaction with the active site residues of GST in solution. Using the GSH-functionalized PDA sensor, we successfully detected GST and GST-human growth hormone (GST-hGH) by the blue-to-purple chromatic transitions. As this PDA colorimetric sensor is simple, rapid, and detectable by the naked eye without protein gel electrophoresis, this strategy is of great practical value as a point-of-care testing sensor for the expression of GST-fusion protein.

Order-Disorder transition of carboxyl terminated chains in polydiacetylenes vesicles probed by second harmonic generation and two-photon fluorescence

To understand and control the interfacial properties of polydiacetylenes (PDAs) vesicles with π-conjugated backbone is very important for their colorimetric sensing of chemical and biological targets. In this work, we adopted 10, 12-pentacosadiynoic acid (PCDA) as the model molecule to prepare PDAs vesicles in aqueous solution with different forms (from monomer to blue-to-purple-to-red phase) by controlling the UV irradiation dose. The variations of the interfacial conformation of PDAs vesicles during chromatic transitions were inspected by the adsorption behaviors of probe molecules (4-(4-diethylaminostyry)-1-methylpyridinium iodide, D289) on vesicle surface with surface-specific second harmonic generation (SHG) and zeta potential measurements. Resonant SHG signal from D289 adsorbed on vesicle surface attenuated sharply, and the adsorption free energy as well as the corresponding two-photon fluorescence signal decreased slightly in chromatic transitions. While, the change in the surface density of the adsorbed D289 molecules for PDAs vesicles with different forms was relatively small as estimated from zeta potential measurements. The attenuation of the SHG intensity was thus attributed to the overall order-disorder transition and the changed orientation of D289 molecules caused by the gradual distortion of carboxyl head group driven by backbone perturbation.

Temperature-Dependent Phase Behavior of Langmuir Films of 10,12-Pentacosadiynoic Acid at the Air/Water Interface and Its Effects on Chromatic Stability of the Polymerized Langmuir-Schaefer Films

The effect of temperature on the two-dimensional phase of 10,12-pentacosadiynoic acid (PCDA) Langmuir films at the air/water interface was investigated. The temperature of the Langmuir films was precisely controlled from 5 to 50 °C and their surface isotherms and in-situ visible absorption spectra were acquired. Depending on the temperature, the PCDA Langmuir films were found to be classified into a liquid-condensed (low temperatures, 5 and 25 °C) and a liquid-expanded phase (high temperatures, 40 and 50 °C). After polymerizing the PCDA Langmuir films with 254 nm UV light at the specific temperatures, the films were transferred to hydrophobic glass using the Langumir-Schaefer (LS) method. Upon thermal and pH stimuli, their chromatic transition characteristics were analyzed by visible spectroscopy. The liquid-condensed films were found to be more susceptible to thermal stimulus than the liquid-expanded films. The latter also showed remarkable chromatic stability against the pH in the region from 2 to 11, compared to the former. Thus, when sturdy films are required, the multilayered PCDA LS films prepared at the liquid-expanded phase are more suitable than the liquid-condensed films, and vice versa. This result is expected to be very useful for controlling the sensitivity and stability of polydiacetylene-based sensory systems simply by changing the polymerization temperature, even without synthesizing new monomers.

Multi-stimuli-responsiveness of a novel polydiacetylene-based supramolecular gel.

Herein, a novel supramolecular gel was fabricated through the bi-component co-assembly strategy of commercially available 10,12-pentacosadiynoic acid (PCDA) and laboratory-synthesized amphiphilic co-gelator N-(2-(1H-imidazol-4-yl)ethyl)stearamide (IMSA), which contains one imidazole head group and a long alkyl chain tail, by synergetic noncovalent interactions. Upon irradiation of normal 254 nm UV light, blue polydiacetylene (PDA) could be obtained by topo-polymerization of the PCDA monomers in the gel phase. This PDA-based supramolecular gel is able to respond to various environmental stimuli and shows a blue-to-red chromatic transition, which could be observed by the naked eye. Specifically, upon exposure to heat, pH, metal cation and organic solvent stimuli, the PDA gel displays thermochromism, halochromism, ionochromism and solvatochromism, respectively. More interestingly, the differences of the above-mentioned stimuli-induced color transition of the blue PDA supramolecular gels could be characterized by UV-Vis absorption spectra and Raman spectra, therefore illuminating a bright application prospect in the area of chemosensing.