Design and preparation of triphenylamine-based polymeric materials towards emergent optoelectronic applications

Biomimetic Exploration and Reflection on Switchable Coordination and Narrow-Band Electrofluorochromic Devices

Electrofluorochromic (EFC) materials and devices with controllable fluorescence properties show great application potential in advanced anticounterfeiting, information storage and display. However, the low color purity caused by the broad emission spectra and underperforming switching time of the existing EFC materials limit their application. Through biomimetic exploration and the study of reversible electrochemical responsive coordination reactions, boron-nitrogen embedded polyaromatics (B,N-PAHs) with narrow-band emission and high color purity have been successfully integrated into EFC systems, which also help to better understand the role of boron in biological activity. The EFC device achieve good performance containing quenching efficiency greater than 90% within short switching time (ton: 0.6 s, toff: 2.4 s), and nearly no performance change after 200 cycles test. Three primary color (red, green, and blue) EFC devices are successfully prepared. In addition, new phenomena are obtained and discussed in this biomimetic exploration of related boron reactions. The success and harvest of this exploration are expected to provide new ideas for optimizing properties and broadening applications of EFC materials. Moreover, it may provide ideas and reference significance for further exploring and understanding the function of boron compounds in biological systems.

Gold Nanoparticles with N-Heterocyclic Carbene/Triphenylamine Surface Ligands: Stable and Electrochromically Active Hybrid Materials for Optoelectronics

Organic-hybrid particle-based materials are increasingly important in (opto)electronics, sensing, and catalysis due to their printability and stretchability as well as their potential for unique synergistic functional effects. However, these functional properties are often limited due to poor electronic coupling between the organic shell and the nanoparticle. N-heterocyclic carbenes (NHCs) belong to the most promising anchors to achieve electronic delocalization across the interface, as they form robust and highly conductive bonds with metals and offer a plethora of functionalization possibilities. Despite the outstanding potential of the conductive NHC-metal bond, synthetic challenges have so far limited its application to the improvement of colloidal stabilities, disregarding the potential of the conductive anchor. Here, NHC anchors are used to modify redox-active gold nanoparticles (AuNPs) with conjugated triphenylamines (TPA). The resulting AuNPs exhibit excellent thermal and redox stability benefiting from the robust NHC-gold bond. As electrochromic materials, the hybrid materials show pronounced color changes from red to dark green, a highly stable cycling stability (1000 cycles), and a fast response speed (5.6 s/2.1 s). Furthermore, TPA-NHC@AuNP exhibits an ionization potential of 5.3 eV and a distinct out-of-plane conductivity, making them a promising candidate for application as hole transport layers in optoelectronic devices.

Effects of Planarization of the Triphenylamine Unit on the Electronic and Transport Properties of Triarylamine-Fluorene Copolymers in Both Doped and Undoped Forms

Triarylamine-alt-fluorene (TAF) copolymers are widely used for hole injection and transport in organic electronics. Despite suggestions to planarize the triphenylamine moiety, little research has been conducted. Here, we report a comprehensive investigation of the effects of planarization on the electronic and transport properties of a model TAF polymer semiconductor core. We compared the conventional twisted-propeller N-4-methoxyphenyl-N,N-diphenylamine-4',4″-diyl (TA) unit and its planarized bridged analogue (bTA) where adjacent o,o'-positions are linked by 1,1-dimethylmethylene. We studied both polyelectrolyte and non-polyelectrolyte forms of this core in both doped and undoped states. We found that planarization leads to an unprecedented trap-free transport of holes, and a pronounced enhancement of their mobility in the undoped state though less so in the doped state. Planarization also induces a slight reduction in the ionization energy of the undoped polymer, consequently lowering the work function of the doped polymer. This is accompanied by small spectral shifts: a red shift in the first absorption band of the undoped polymer and a blue shift in the first absorption band of the polaron. Furthermore, this study unveils new fundamental features of TAF polymers: (i) Doping induces the formation of three polaron bands within the subgap. (ii) Absorption of both neutral and polaron segments exhibit a linear intensity relationship with doping level. (iii) Electrical conductivity reaches a maximum at the half-doped state, varying as σ ∼ (x (1 - x))3 for 0.1 ≲ x ≲ 0.9, where x is the doping level. Finally, we demonstrate the successful integration of these self-compensated hole-doped TAF polymers as efficient hole injection layers in organic semiconductor diodes.

Triangular Triazine-Triphenylamine Functionalized Hybrid Fluorescent Porous Polymers for Detection and Photodegradation of Tetracycline Hydrochloride

First, an organic semiconductor fluorescent molecule of 4',4″,4"'-(2,4,6-triphenyl-1,3,5-triazine)-4-(N,N-diphenyl-(1,1'-biphenyl)-4-amine (TPTz) is successfully synthesized by the Suzuki-Miyaura coupling reaction of 2,4,6-tris(4-bromophenyl)-1,3,5-triazine with 4-(diphenylamino)phenylboronic acid. TPTz offers as high as 85% fluorescence quantum yield and a strong solvent effect, with fluorescent colors across the visible spectrum in different solvents. Then, an organic-inorganic hybrid fluorescent porous polymer of PCS-TPTz with a surface area of 714 m2 g-1 and pore volume of 0.660 cm3 g-1 is prepared by the Friedel-Crafts reaction of TPTz and octavinylsilsesquioxane; PCS-TPTz showed a high fluorescence quantum yield of 17% with a large Stokes shift of up to 280 nm. The excellent fluorescence properties and insolubility of PCS-TPTz make it to act as a heterophase sensor for tetracycline hydrochloride (TH) with a KSV of 2.39 × 104 M-1. In addition, PCS-TPTz exhibits an excellent photodegradation activity for antibiotic TH without the requirement for additional oxidants or pH adjustments. ESR spectra and free radical trapping experiment indicate that superoxide radical (•O2-) is the active radical for achieving the photodegradation. The simultaneous detection and degradation of TH are achieved by PCS-TPTz.

Redox-Stable and Multicolor Electrochromic Polyamides with Four Triarylamine Cores in the Repeating Unit

Two new triarylamine-based diamine monomers, namely, N,N'-bis(4-methoxyphenyl)-N,N'-bis(4-(4-aminophenyl-4'-methoxyphenylamino)phenyl)-p-phenylenediamine (3) and N,N'-bis(4-methoxyphenyl)-N,N'-bis(4-((4-aminophenyl-1-naphthyl)amino)phenyl)-p-phenylenediamine (7), were successfully synthesized and led to two series of electroactive polyamides by polycondensation reactions with common aromatic dicarboxylic acids. The polymers demonstrated multicolored electrochromism, high optical contrast, and remarkable enhancements in redox and electrochromic stability. Compared to other triarylamine-based polymers, the studied polyamides exhibited enhanced electrochromic stability (only 3~6% decay of its coloration efficiency at 445 nm after 14,000 switching cycles) at the first oxidation stage. The polyamides also showed strong absorption in the near-infrared region upon oxidation. Polymers with multicolored electrochromism and high redox stability can be developed by incorporation of four triarylamine cores in each repeat unit and electron-donating methoxy groups on the active sites of the triphenylamine units.

One-Step Catalyst-Transfer Macrocyclization: Expanding the Chemical Space of Azaparacyclophanes

In this paper, we report on a one-step catalyst-transfer macrocyclization (CTM) reaction, based on the Pd-catalyzed Buchwald-Hartwig cross-coupling reaction, selectively affording only cyclic structures. This route offers a versatile and efficient approach to synthesize aza[1n]paracyclophanes (APCs) featuring diverse functionalities and lumens. The method operates at mild reaction temperatures (40 °C) and short reaction times (∼2 h), delivering excellent isolated yields (>75% macrocycles) and up to 30% of a 6-membered cyclophane, all under nonhigh-dilution concentrations (35-350 mM). Structural insights into APCs reveal variations in product distribution based on different endocyclic substituents, with steric properties of exocyclic substituents having minimal influence on the macrocyclization. Aryl-type endocyclic substituents predominantly yield 6-membered macrocycles, while polycyclic aromatic units such as fluorene and carbazole favor 4-membered species. Experimental and computational studies support a proposed mechanism of ring-walking catalyst transfer that promotes the macrocycle formation. It has been found that the macrocyclization is driven by the formation of cyclic conformers during the oligomerization step favoring an intramolecular C-N bond formation that, depending on the cycle size, hinges on either preorganization effect or kinetic increase of the reductive elimination step or a combination of the two. The CTM process exhibits a "living" behavior, facilitating sequential synthesis of other macrocycles by introducing relevant monomers, thus providing a practical synthetic platform for chemical libraries. Notably, CTM operates both under diluted and concentrated regimes, offering scalability potential, unlike typical macrocyclization reactions usually operating in the 0.1-1 mM range.

Synthesis of Cycloaliphatic Polyamides via Palladium-Catalyzed Hydroaminocarbonylative Polymerization

Polyamides represent one class of materials that is important in modern society. Because of the numerous potential applications of polyamides in various fields, there is a high demand for new polyamide structures, which necessitates the development of new polymerization methods. Herein, we report a novel and efficient palladium-catalyzed hydroaminocarbonylative polymerization of dienes and diamines for the synthesis of cycloaliphatic polyamides. The method employs readily available starting materials, proceeds in an atom-economic manner, and creates a series of new functional polyamides in high yields and high molecular weights. In contrast with the traditional polyamides based on adipic acid, the cycloaliphatic polyamides have superior thermal resistance, higher glass-transition temperature, and better solubility in common organic solvents, thus probably featuring the merits of high-performance and good processability.

Access to 2,4-Disubstituted Pyrrole-Based Polymer with Long-Wavelength and Stimuli-Responsive Properties via Copper-Catalyzed [3+2] Polycycloaddition

Pyrrole-based polymers (PBPs), a type of fascinating functional polymers, play a crucial role in materials science. However, efficient synthetic strategies of PBPs with diverse structures are mainly focused on conjugated polypyrroles and still remain challenging. Herein, an atom and step economy protocol is described to access various 2,4-disubstituted PBPs by in situ formation of pyrrole core structure via copper-catalyzed [3+2] polycycloaddition of dialkynones and diisocyanoacetates. A series of PBPs is prepared with high molecular weight (Mw up to 18 200 Da) and moderate to good yield (up to 87%), which possesses a fluorescent emission located in the green to yellow light region. Blending the PBPs with polyvinyl alcohol, the stretchable composite films exhibit a significant strengthening of the mechanical properties (tensile stress up to 59 MPa, elongation at break >400%) and an unprecedented stress-responsive luminescence enhancement that over fourfold fluorescent emission intensity is maintained upon stretching up to 100%. On the basis of computational studies, the unique photophysical and mechanical properties are attributed to the substitution of carbonyl chromophores on the pyrrole unit.

Multifunctional Ultrathin Metasurface with a Low Radar Cross Section and Variable Infrared Emissivity

The development of stealth devices that are compatible with both infrared (IR) and radar systems remains a significant challenge, as the material properties required for effective IR and radar stealth are often contradictory. In this work, based on an IR electrochromic device (IR-ECD), concepts of metamaterial manipulating electromagnetic waves are applied to develop a multifunctional ultrathin metasurface with a low radar cross section (RCS) and variable infrared emissivity. This paper presents a linear-to-linear polarization conversion metasurface (PCM) designed by hollowing the IR-ECD. In this way, the IR-ECD based on polyaniline (PANI) can also modulate the reflection waves in the microwave band without affecting its features in the infrared region. Thus, the proposed metasurface integrates both microwave stealth and variable infrared emissivity through a single layer. The measured results show that a 10 dB RCS reduction is achieved in the band of 8.46-9.5 GHz, and the infrared emissivity can be adjusted from 0.870 to 0.513 in the infrared stealth band of 8-14 μm. Due to the ultrathin thickness (only 0.081λ0 at 9 GHz), low RCS in the X-band, and variable infrared emissivity, the designed multifunctional stealth metasurface has promising applications on military platforms with various surrounding environments.

Naphthyl Substituted Impurities Induce Efficient Room Temperature Phosphorescence

Accidentally, it was found that triphenylamine (TPA) from commercial sources shows ultralong yellow-green room temperature phosphorescence (RTP) like commercial carbazole, which however disappears for lab-synthesized TPA with high purity. Herein, we for the first time identify the impurity types that cause RTP of commercial TPA, which are two N, N-diphenyl-naphthylamine isomers. Due to similar molecular polarity and very trace amount (≈0.8 ‰, molar ratio), these naphthyl substituted impurities can be easily overlooked. We further show that even at an extremely low amount (1000000 : 1, mass ratio) of impurities, RTP emission is still generated, attributed to the triplet-to-triplet energy transfer mechanism. Notably, this doping strategy is also applicable to the triphenylphosphine and benzophenone host systems, of which strong RTP emission can be activated by simply doping the corresponding naphthyl substituted analogues into them. This work therefore provides a general and efficient host/guest strategy toward high performance and diverse organic RTP materials.

Reversible Electrochromic/Electrofluorochromic Dual Switching in Zn(II)-Based Metallo-Supramolecular Polymer Films

The introduction of novel materials with multifunctional chromogenic properties, such as electrochromic/electrofluorochromic (EC/EFC) properties, has recently attracted prospective interest in the development of various optoelectronic devices and smart windows. In this study, a novel Zn(II)-based metallo-supramolecular polymer (polyZn) has been developed as an ON/OFF switchable EFC application with prominent EC behavior. In this regard, the polymeric chain of polyZn was first synthesized by 1:1 complexation in a zigzag manner with Zn(II) ions at the metal center and 4,4'-[bis(2,2':6',2″-terpyridinyl)benzene]triphenylamine (LTPY-TPA) as the redox-active ditopic ligand. The polyZn exhibits excellent solubility in organic solvents and can form a very good uniform thin film on an indium tin oxide/glass substrate by spin-coating. In a neutral state, transparent polyZn exhibits a bright yellow color to the naked eye (absorption at ∼325 nm). The electroactive triphenylamine (TPA) core of LTPA-TPY, however, undergoes reversible single-electron oxidation when a positive bias of +1.6 V vs Ag/Ag+ is applied, generating radical cations (TPA ↔ TPA•+) with a significant drop in transparency (77%). A noticeable chromic shift in the hue of the film from brilliant yellow to green was observed with the appearance of a near-infrared absorption band at ∼897 nm with a tail of 1300-1600 nm. Interestingly, in addition to this EC phenomenon, the fabricated solid-state polyZn film exhibits intense, high-contrast reddish-orange photoluminescence with λem = 650 nm, which is significantly desired as a molecular probe for bioimaging. Both the TPA core and the redox-inactive Zn(II)-terpyridine core emit orange-red photoluminescence in polyZn, which is significantly quenched upon the oxidation of the film and is re-emitted at 0.0 V vs Ag/Ag+. This ON/OFF EFC transition was sustained for several cycles. This study should motivate to design and create distinctive new unique materials with combined EC/EFC behavior for the fabrication of optoelectronic devices by combining a metal-fluorescent core with a redox-active spacer.

Survey of Recent Advances in Molecular Fluorophores, Unconjugated Polymers, and Emerging Functional Materials Designed for Electrofluorochromic Use

In this review, recent advances that exploit the intrinsic emission of organic materials for reversibly modulating their intensity with applied potential are surveyed. Key design strategies that have been adopted during the past five years for developing such electrofluorochromic materials are presented, focusing on molecular fluorophores that are coupled with redox-active moieties, intrinsically electroactive molecular fluorophores, and unconjugated emissive organic polymers. The structural effects, main challenges, and strides toward addressing the limitations of emerging fluorescent materials that are electrochemically responsive are surveyed, along with how these can be adapted for their use in electrofluorochromic devices.

Photodetection Enhancement via Graphene Oxide Deposition on Poly 3-Methyl Aniline

A graphene oxide (GO)/poly 3-methyl aniline (P3MA) photodetector has been developed for light detection in a broad optical region: UV, Vis, and IR. The 3-methyl aniline was initially synthesized via radical polymerization using an acid medium, i.e., K₂S₂O₈ oxidant. Consequently, the GO/P3MA composite was obtained through the adsorption of GO into the surface of P3MA. The chemical structure and optical properties of the prepared materials have been illustrated via XRD, FTIR, SEM, and TEM analysis. The absorbance measurements demonstrate good optical properties in the UV, Vis, and near-IR regions, although a decrease in the bandgap from 2.4 to 1.6 eV after the composite formation was located. The current density (J_ph) varies between 0.29 and 0.68 mA·cm^-2 (at 2.0 V) under dark and light, respectively. The photodetector has been tested using on/off chopped light at a low potential, in which the produced J_ph values decrease from 0.14 to 0.04 µA·cm^-2, respectively. The GO/P3MA photodetector exhibits excellent R (and D) values of 4 and 2.7 mA·W^-1 (0.90 × 10⁹ and 0.60 × 10⁹ Jones) in the UV (340 nm) and IR (730 nm) regions, respectively. The R and D values obtained here make the prepared photodetector a promising candidate for future light detection instruments.

Ring Repeating Unit: An Upgraded Structure Representation of Linear Condensation Polymers for Property Prediction

Unique structure representation of polymers plays a crucial role in developing models for polymer property prediction and polymer design by data-centric approaches. Currently, monomer and repeating unit (RU) approximations are widely used to represent polymer structures for generating feature descriptors in the modeling of quantitative structure-property relationships (QSPR). However, such conventional structure representations may not uniquely approximate heterochain polymers due to the diversity of monomer combinations and the potential multi-RUs. In this study, the so-called ring repeating unit (RRU) method that can uniquely represent polymers with a broad range of structure diversity is proposed for the first time. As a proof of concept, an RRU-based QSPR model was developed to predict the associated glass transition temperature (T_g) of polyimides (PIs) with deterministic values. Comprehensive model validations including external, internal, and Y-random validations were performed. Also, an RU-based QSPR model developed based on the same large database of 1321 PIs provides nonunique prediction results, which further prove the necessity of RRU-based structure representation. Promising results obtained by the application of the RRU-based model confirm that the as-developed RRU method provides an effective representation that accurately captures the sequence of repeat units and thus realizes reliable polymer property prediction by data-driven approaches.

Synthesis and Characterization of Novel Triphenylamine-Containing Electrochromic Polyimides with Benzimidazole Substituents

Two novel electrochromic aromatic polyimides (named as TPA-BIA-PI and TPA-BIB-PI, respectively) with pendent benzimidazole group were synthesized from 1,2-Diphenyl-N,N'-di-4-aminophenyl-5-amino-benzimidazole and 4-Amino-4'-aminophenyl-4″-1-phenyl-benzimidazolyl-phenyl-aniline with 4,4'-(hexafluoroisopropane) phthalic anhydride (6FDA) via two-step polymerization process, respectively. Then, polyimide films were prepared on ITO-conductive glass by electrostatic spraying, and their electrochromic properties were studied. The results showed that due to the π-π* transitions, the maximum UV-Vis absorption bands of TPA-BIA-PI and TPA-BIB-PI films were located at about 314 nm and 346 nm, respectively. A pair of reversible redox peaks of TPA-BIA-PI and TPA-BIB-PI films that were associated with noticeable color changed from original yellow to dark blue and green were observed in the cyclic voltammetry (CV) test. With increasing voltage, new absorption peaks of TPA-BIA-PI and TPA-BIB-PI films emerged at 755 nm and 762 nm, respectively. The switching/bleaching times of TPA-BIA-PI and TPA-BIB-PI films were 13 s/16 s and 13.9 s/9.5 s, respectively, showing that these polyimides can be used as novel electrochromic materials.

Catalyst-free synthesis of diverse fluorescent polyoxadiazoles for the facile formation and morphology visualization of microporous films and cell imaging

The development of facile polymerizations toward functional heterocyclic polymers is of great significance for chemistry and materials science. As an important class of heterocyclic polymers, polyoxadiazoles (PODs) have found applications in various fields. However, the synthetic difficulties of PODs greatly restrict their structural diversity and property investigation. Herein, we report a series of catalyst-free multicomponent polymerizations (MCPs) that can facilely synthesize functional PODs with well-defined and diversified topological structures from commercially available or readily accessible aldehydes, carboxylic acids, secondary amines, and (N-isocyanimino)triphenylphosphorane at room temperature. Unlike conventional Ugi polycondensations, the present Ugi-type MCPs can in situ generate oxadiazole moieties in polymer backbones. The obtained PODs possess good solubility, high thermal and morphological stability, and excellent film-forming ability. The introduction of aggregation-induced emission (AIE) moieties together with the inherent structural features of PODs endow these polymers with multiple functionalities. The AIE-active linear PODs can form fluorescent microporous films with stable and ordered structures based on the simple breath figure patterning method, and the self-assembly morphologies can be directly visualized by fluorescence microscopy in a high-contrast and sensitive manner. Moreover, both the linear and hyperbranched AIE-active PODs possess excellent biocompatibility, good lysosome specificity, and excellent photobleaching resistance, which enable them to serve as promising lysosome-specific fluorescent probes in biological imaging.

Emerging Electrochromic Materials and Devices for Future Displays

With the rapid development of optoelectronic fields, electrochromic (EC) materials and devices have received remarkable attention and have shown attractive potential for use in emerging wearable and portable electronics, electronic papers/billboards, see-through displays, and other new-generation displays, due to the advantages of low power consumption, easy viewing, flexibility, stretchability, etc. Despite continuous progress in related fields, determining how to make electrochromics truly meet the requirements of mature displays (e.g., ideal overall performance) has been a long-term problem. Therefore, the commercialization of relevant high-quality products is still in its infancy. In this review, we will focus on the progress in emerging EC materials and devices for potential displays, including two mainstream EC display prototypes (segmented displays and pixel displays) and their commercial applications. Among these topics, the related materials/devices, EC performance, construction approaches, and processing techniques are comprehensively disscussed and reviewed. We also outline the current barriers with possible solutions and discuss the future of this field.

Investigation on the binary ionization choices for large conjugated amines during electrospray ionization

RATIONALE

Generally, amines form protonated cations ([M + H]⁺ ) in positive polarity during electrospray ionization (ESI). However, it was found that large conjugated amines (LCAs) had binary ionization choices of generating either radical cations (M^•+ ) or [M + H]⁺ during ESI. Investigation on the mechanism would further our understanding of ESI.

METHODS

In this work, the binary ionization behavior of LCAs was reported and studied. Internal factors (functional groups and sizes of conjugated systems) and external factors (solvent type, flow rate, and electrode position) were systematically investigated and discussed.

RESULTS

For the internal factors, electron-donating groups and large conjugated structures of LCAs were conducive to the generation of M^•+ . For the external factors, aprotic solvent, higher flow rate, and shorter distance from the electrode to the spray cone facilitated the formation of M^•+ but hampered the generation of [M + H]⁺ .

CONCLUSION

The present study illustrated that the formations of M^•+ and [M + H]⁺ for LCAs were two independent processes. The M^•+ cations of LCAs were formed on the surface of the electrode through electrochemical oxidation, whereas the [M + H]⁺ cations were generated following the typical ESI evolution process. By regulating the external factors, the ionization results of LCAs could be well modulated.

Poly-3-Methyl Aniline-Assisted Spherical PbS Quantum Dots through the Ionic Adsorption Deposition Method as a Novel and Highly Efficient Photodetector in UV, Vis, and NIR Regions

This study describes the preparation and characterization of glass/poly-3-methyl aniline (P3MA)/PbS quantum dot (QD) optoelectronic photodetector to detect and sense the light in broad spectral regions of UV, Vis, and NIR. This work is carried out to solve the drawbacks of other studs that prepare detectors in just one or two optical regions. Previous studies have used high-priced techniques. The deposition of P3MA on the glass surface was carried out by in situ oxidation process. Then, this polymer film was used to assist the deposition of PbS-QD particles through the ionic adsorption deposition method. The latter was performed using four different concentrations of Pb(NO3)2 solution (0.01, 0.03, 0.05, and 0.07 M) to form four P3MA/PbS composites: I, II, III, and IV, respectively. The chemical structure, morphologies, and electrical and optical properties of these composites were determined using different analytical tools. The SEM confirmed the formation of spherical QD particles of PbS on the P3MA surface. The TEM analysis showed that the composite has an average size of 5 nm, with the interatomic distances of 0.4 nm. Furthermore, the optical band gap values were 1.53, 1.52, 1.50, and 1.51 eV, respectively. The optoelectronic device could detect and sense light from 390 to 636 nm under various optical wavelengths. The produced current density ( $J_{\text{ph}}$ ) values decreased from 0.029 mA.cm-2 at 390 nm to 0.022 mA.cm-2 at 500 nm and then increased until 0.024 mA.cm-2 at 636 nm. The light sensing was determined through the photoresponsivity ( $R$ ) and detectivity ( $D$ ) parameters, in which the photodetector has $R$ and $D$ values of 0.29 mA.cm-2 and $6.5\times {10}^7$ Jones, respectively. Finally, a simple mechanism was proposed to explain the light sensing through the prepared optoelectronic device. Soon, our team works on the industrial applications of this optoelectronic device in the industry field related to the great optoelectronic device technical properties and its low cost and easy preparation.

Topological Design of Highly Anisotropic Aligned Hole Transporting Molecular Bottlebrushes for Solution-Processed OLEDs

Polyvinyl polymers bearing pendant hole transport functionalities have been extensively explored for solution-processed hole transport layer (HTL) technologies, yet there are only rare examples of high anisotropic packing of the HT moieties of these polymers into substrate-parallel orientations within HTL films. For small molecules, substrate-parallel alignment of HT moieties is a well-established approach to improve overall device performance. To address the longstanding challenge of extension from vapor-deposited small molecules to solution-processable polymer systems, a fundamental chemistry tactic is reported here, involving the positioning of HT side chains within macromolecular frameworks by the construction of HT polymers having bottlebrush topologies. Applying state-of-the-art polymer synthetic techniques, various functional subunits, including triphenylamine (TPA) for hole transport and adhesion to the substrate, and perfluoro alkyl-substituted benzyloxy styrene for migration to the air interface, were organized with exquisite control over the composition and placement throughout the bottlebrush topology. Upon assembling the HT bottlebrush (HTB) polymers into monolayered HTL films on various substrates through spin-casting and thermal annealing, the backbones of HTBs were vertically aligned while the grafts with pendant TPAs were extended parallel to the substrate. The overall design realized high TPA π-stacking along the out-of-plane direction of the substrate in the HTLs, which doubled the efficiency of organic light-emitting diodes compared with linear poly(vinyl triphenylamine)s.

Investigation of electrochemistry and electrochromic performance of metallopolymer formed by electropolymerization of Fe(II) complex with triphenylamine-hydrazone ligand

The complex of Fe(II) ions of general formula [FeL2](BF4)2 with triphenylamine-hydrazone ligand L has been synthesized and characterized. Oxidative electropolymerization of the complex proceeded smoothly on the working electrode producing homogenous thin film of metallopolymer. The film thickness and morphology of the layer was investigated by microscopy techniques such as SEM and AFM, and the composition of the film was confirmed by XPS analysis. It was found that after fifty successive oxidation/reduction cycles the film of thickness 120 nm was formed on the electrode surface. The metallopolymer was also characterized using cyclic voltammetry and spectroelectrochemical methods. The film was found to change its color from yellow to green-blue, high change in transmittance of 60% at 770 nm and good electrochemical stability during 375 cycles of switching of the potential between -0.1 V and +1.5 V, due to the presence of metal ions that link two ligand molecules resulting in formation of highly cross-linked film. The switching times (coloration and bleaching) were calculated to be 34.2 s and 7.3 s, respectively. Coloration efficiency of the formed film of polymeric complex was found to be 144 cm 2 /C.

From gas separation to ion transport in the cavity of hyperbranched polyamides based on triptycene aimed for electrochromic and memory devices

Introducing 3D triptycene as core with methoxy-diphenylamine into hyper- branching polyamides will greatly improve robust electrochemical cycling stability crucial for the application of ECDs.

Effects of the number and position of methoxy substituents on triphenylamine-based chalcone visible-light-absorbing photoinitiators

Five visible-light-absorbing triphenylamine-based chalcone photoinitiators (CY1–CY5) have been synthesized for application in free radical photopolymerization.

Synthesis and electrochromic properties of polyamines containing a 4,4′-diaminotriphenylamine-N,N′-diyl unit in the polymer backbone: Ru-catalyzed N–H insertion polycondensation of 1,4-phenylenebis(diazoacetate) with 4,4′-diaminotriphenylamine derivatives

Polycondensation of a bis(diazocarbonyl) compound and diaminotriphenylamine derivatization via Ru-catalyzed N–H insertion to afford electroactive polyamine.

Highly electrochemically and thermally stable donor–π–acceptor triphenylamine-based hole-transporting homopolymers via oxidative polymerization

Polymers combining high electrochemical and thermal stability, good solubility, high Tg and high coke residue with low-lying HOMO levels and reasonable hole mobilities in thin films are reported in this study.

An Active Catalyst System Based on Pd (0) and a Phosphine-Based Bulky Ligand for the Synthesis of Thiophene-Containing Conjugated Polymers

To address the limitations of conventional Pd catalysts in the polymerization of thiophene-containing conjugated polymers, an active catalyst system based on Pd (0) and a phosphine-based bulky ligand, L1, is explored systematically in Suzuki–Miyaura polymerizations using thiophene boronic acid pinacol ester as one of the monomers. This active catalyst is found very efficient in synthesizing a series of thiophene-containing linear and hyperbranched conjugated polymers. First, as a model example, coupling reactions between electron-rich/moderately hindered aryl or thienyl halides and thiophene boronic acid pinacol ester give excellent yields with lower catalyst loading and can be completed in a shorter reaction time relative to Pd(PPh₃)₄. Notably, high molecular weight thiophene-containing polymers are successfully synthesized by Suzuki–Miyaura polycondensation of 2,5-thiophene bis(boronic acid) derivatives with different dibromo- and triple bromo-substituted aromatics in 5–15 min.

Electropolymerization of D–A–D type monomers consisting of triphenylamine and substituted quinoxaline moieties for electrochromic devices

We reported three D–A–D type monomers consisting of triphenylamine and substituted quinoxaline moieties, and their electrochemical polymerization for electrochromic devices.

Solubility, thermal and photoluminescence properties of triphenyl imidazole-containing polyimides

In this paper, three kinds of triphenyl imidazole-containing diamines including 2-phenyl-4,5-bis(4-(4-amino-2-trifluoromethylphenoxy)phenyl)imidazole (PBAI), 2-(4-methylphenyl)-4,5-bis(4-(4-amino-2-trifluoromethyl phenoxy)phenyl)imidazole (MPBAI) and 2-(4-trifluoromethylphenyl)-4,5-bis(4-(4-amino-2-trifluoromethylphenoxy)phenyl)imidazole (TFPBAI) were synthesized. Then, a series of polyimide (PI) films were prepared by the solution polymerization of the three diamines and various dianhydrides, such as 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 1,2,4,5-pyromellitic dianhydride (PMDA) and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), followed by thermal imidization. The effects of chemical structures on the solubilities and thermal, optical and electrochemical properties of polyimides were explored. All the polyimides exhibited higher glass transition temperatures around 300 °C and excellent solubilities in common polar solvents. The polyimide films derived from CBDA or 6FDA showed better optical properties with light color and transparent characteristics. The fluorescence test showed that the photoluminescence color of CBDA-based polyimide films is in the blue range in the CIE 1931 spectrum, while the polyimide film based on PMDA and 6FDA presented black or weak yellow light. However, all these polyimides in solution exhibited similar blue luminescence. Electrochemical tests indicated that the HOMO and LUMO values of these films were around −6.5 and −3.6 eV, and the energy gap difference was about 3.0 eV. Therefore, the triphenyl imidazole-containing polyimides exhibit comprehensive performance, which will be expected as a new kind of functional material for certain application in the optical and optoelectronics fields.

The triphenyl imidazole-containing polyimide films exhibit excellent solubility and thermal and photoluminescence properties.

Electrosynthesis and Electrochromism of a New Crosslinked Polydithienylpyrrole with Diphenylpyrenylamine Subunits

A new electroactive monomer with two 2,5-di(2-thienyl)pyrrole (SNS) units and one diphenylpyrenylamine (DPPA) subunit, namely N,N-bis(4-(2,5-di(2-thienyl)-1H-pyrrol-1-yl)-phenyl)-1-aminopyrene (DPPA-2SNS), was synthesized from 1,4-di-(2-thienyl)butane-1,4-dione with N,N-di(4-aminophenyl)-1-aminopyrene through the Paal–Knorr condensation reaction. Visible and near-infrared (NIR) electrochromic polymer films could be facilely generated on the ITO-glass surface by the electrochemical polymerization of DPPA-2SNS in an electrolyte solution. The electro-synthesized polymer films exhibit multi-staged redox processes and multi-colored anodic electrochromic behavior. A multi-colored electrochromism, with yellowish orange, greyish blue, and purplish black colors, was observed in the polymer film by applying a positive potential. The polymer films exhibit reasonable coloration efficiency, fast response time, and good cycling stability, especially when switched between neutral and the first oxidation states. For comparison, N-(1-pyrenyl)-2,5-di(2-thienyl)pyrrole (Py-SNS) was also prepared and characterized with electrochemical and electro-optical properties.

Yellow-to-brown and yellow-to-green electrochromic devices based on complexes of transition metal ions with a triphenylamine-based ligand

Transmissive-to-colored electrochromism has been achieved by combination of MLCT of transition metal complexes with the electrochromic properties of ligand molecules. The color transitions were from yellow to dark brown for the Fe(ii) complex, yellow to orange to bluish-green for the Co(ii) complex and yellow to green for the Zn(ii) complex. By using a metal ion-ligand coordination approach, the self-assembly of hydrazone-based ligands containing a triphenylamine group with appropriate metal salts (FeCl2, Co(ClO4)2 and Zn(BF4)2) produced novel complexes of the general formula [ML2]X2. The isolated complexes were characterized by spectroscopic methods, and the Co(ii) complex also by X-ray diffraction analysis. Thin films of the complexes have been obtained by a spray-coating method and they were used in the construction of electrochromic devices, which showed good electrochromic stability, a high color contrast of 47.5% for Fe(ii), 37.2% for Co(ii) and 33.7% for Zn(ii) complexes and fast coloring and bleaching times.