A Novel Electrochromic Polymer Synthesized through Electropolymerization of a New Donor−Acceptor Bipolar System

Electropolymerization of robust conjugated microporous polymer membranes for rapid solvent transport and narrow molecular sieving

Pore size uniformity is one of the most critical parameters in determining membrane separation performance. Recently, a novel type of conjugated microporous polymers (CMPs) has shown uniform pore size and high porosity. However, their brittle nature has prevented them from preparing robust membranes. Inspired by the skin-core architecture of spider silk that offers both high strength and high ductility, herein we report an electropolymerization process to prepare a CMP membrane from a rigid carbazole monomer, 2,2’,7,7’-tetra(carbazol-9-yl)-9,9’-spirobifluorene, inside a robust carbon nanotube scaffold. The obtained membranes showed superior mechanical strength and ductility, high surface area, and uniform pore size of approximately 1 nm. The superfast solvent transport and excellent molecular sieving well surpass the performance of most reported polymer membranes. Our method makes it possible to use rigid CMPs membranes in pressure-driven membrane processes, providing potential applications for this important category of polymer materials.

Conjugated microporous polymers (CMPs) have great potential in membrane applications but are often brittle. Here, the authors develop an electropolymerization process to form a skin-core architecture which allows them to overcome mechanical limitations while keeping the excellent separation performance of CMP membranes.

Colorless-to-Black Electrochromism from Binary Electrochromes toward Multifunctional Displays

Cyclohexane-1,2,4,5-tetracarboxylic diimide with a nonconjugated core has been incorporated to bridge two conventional triphenylamine units. The obtained monomer has successfully hypsochromically shifted the maximum absorption wavelength by 10 nm in comparison to the one with a pyromellitic diimide bridge. Consequently, a colorless electrochromic (EC) polymer poly(bis(N,N-diphenyl-4-aminophenyl)cyclohexane-1,2,4,5-tetracarboxylic diimide) (PTPA-HDI) was electropolymerized on indium tin oxide (ITO)-coated glass. The morphology, absorption, and spectroelectrochemistry properties of polymer PTPA-HDI films electropolymerized by different scan cycles have been systematically investigated. It is found that comprehensive properties, such as color contrast and initial transparence, can be achieved for the polymer film electropolymerized by 15 scan cycles. Moreover, to realize colorless-to-black electrochromism, an asymmetric viologen derivative 1-(4-cyanophenyl)-1'-hexyl-4,4'-bipyridinium dihexafluorophosphate (HVCN) has been designed and straightforward synthesized. With the introduction of a cyanophenyl group and a hexyl chain on the two pyridinium units, colorless-to-green electrochromism can be realized for this processible viologen derivative. The absorption band at 495 nm of colorated PTPA-HDI compensates well for the valley in the absorption spectrum of colorated HVCN. Therefore, different types of colorless-to-black electrochromic devices (ECDs) are fabricated using polymer PTPA-HDI-deposited ITO electrode and HVCN-based gel electrolyte. Such a supporting electrolyte-free ECD with binary electrochromes exhibits fast coloration, high color contrast, and excellent reversibility. Furthermore, an encryption ECD is demonstrated by switching a black two-dimensional code. In addition, an autodigital display is integrated on a smart window and hence different functions can be realized in a single ECD. Overall, this study may facilitate the understanding of the EC behaviors of binary electrochromes and present a new path to design multifunctional displays.

Electropolymerizable IrIII Complexes with β-Ketoiminate Ancillary Ligands

A series of electropolymerizable cyclometallated Ir^III complexes were synthesized and their electrochemical and photophysical properties studied. The triphenylamine electropolymerizable fragment was introduced by using triphenylamine-2-phenylpyridine and, respectively, triphenylamine-benzothiazole as cyclometalated ligands. The coordination sphere was completed by two differently substituted β-ketoiminate ligands deriving from the condensation of acetylacetone or hexafluoroacetylacetone with para-bromoaniline. The influence of the -CH₃ /-CF₃ substitution to the electrochemical and photophysical properties was investigated. Both complexes with CH₃ substituted β-ketoiminate were emissive in solution and in solid state. Highly stable films were electrodeposited onto ITO coated glass substrates. Their emission was quenched by electron trapping within the polymeric network as proven by electrochemical studies. The -CF₃ substitution of the β-ketoiminate leads instead to the quenching of the emission and inhibits electropolymerization.

Improving the Electropolymerization Properties of Fluorene-Bridged Dicarbazole Monomers through Polyfluoroalkyl Side Chains

The facile functionalization of the fluorene scaffold at the 2,7-positions was utilized to provide access to two soluble carbazole-π-carbazole derivatives CFC-H1 and CFC-F1 featuring fully hydrogenated and polyfluorinated alkyl chains at the 9-position of the fluorene π-bridging unit, respectively. The optical and electrochemical properties of the new dicarbazoles were investigated. Their electrochemical polymerization over Pt and indium tin oxide electrodes allowed the generation of electroactive polymeric films, whose physicochemical characteristics were strongly dependent on the kind of alkyl chain present on the fluorene bridge. In particular, the electropolymerization of the polyfluorinated monomer allowed the fabrication of thin films with good electrical conductivity, reversible electrochemical processes, good electrochromic properties, and enhanced water repellency with respect to its nonfluorinated analogue.

Electrochromism in Electropolymerized Films of Pyrene-Triphenylamine Derivatives

Two star-shaped multi-triphenylamine derivatives 1 and 2 were prepared, where 2 has an additional phenyl unit between a pyrene core and surrounding triphenylamine units. The oxidative electropolymerization of 1 and 2 occurred smoothly to give thin films of polymers P1 and P2. The electrochemistry and spectroelectrochemistry of P1 and P2 were examined, showing two-step absorption spectral changes in the near-infrared region. The electrochromic properties, including contrast ratio, response time, and cyclic stability of P1 and P2 were investigated and compared. Thin film of P2 displays slightly better electrochromic performance than P1, with a contrast ratio of 45% at 1475 nm being achieved.

A water-stable 3D Eu-MOF based on a metallacyclodimeric secondary building unit for sensitive fluorescent detection of acetone molecules

A Eu-MOF with high water stability constructed using a systematic metallacyclodimeric motif as a potential chemical sensor for acetone is reported.

A comparative study of redox-active, ambipolar electrochromic triphenylamine-based polyimides prepared by electrochemical polymerization and conventional polycondensation methods

The spectroscopic, electrochemical and electrochromic properties of polyimides with tetraphenylbenzidine (TPB) units prepared by electropolymerization and polycondensation were compared.

Recent advances in triphenylamine-based electrochromic derivatives and polymers

Triphenylamine-containing electrochromic materials with great potential applications in low energy-consumption displays, light-adapting mirrors in vehicles, and smart windows have experienced an exponential growth of research interests. In this review, the newly developed triphenylamine-based derivatives and polymers are reviewed and elaborated.

Electrosynthesis of Aromatic Poly(amide-amine) Films from Triphenylamine-Based Electroactive Compounds for Electrochromic Applications

Two electropolymerizable monomers with a methoxytriphenylamine core linked via amide groups to two triphenylamine (TPA) or N-phenylcarbazole (NPC) terminal groups, namely 4,4'-bis(4-diphenylaminobenzamido)-4''-methoxytriphenylamine (MeOTPA-(TPA)₂) and 4,4'-bis(4-(carbazol-9-yl)benzamido)-4''-methoxytriphenylamine (MeOTPA-(NPC)₂), were synthesized and characterized by FTIR and ¹H NMR spectroscopy, mass spectrometry, and cyclic voltammetry. The electrochemical polymerization reactions of these MeOTPA-cored monomers over indium tin oxide (ITO) electrode allow the generation of electroactive poly(amide-amine) films. The electro-generated polymer films exhibited reversible redox processes and multi-colored electrochromic behaviors upon electro-oxidation, together with moderate coloration efficiency and cycling stability. The optical density changes (ΔOD) were observed in the range of 0.18⁻0.68 at specific absorption maxima, with the calculated coloration efficiencies of 42⁻123 cm²/C. Single-layer electrochromic devices using the electrodeposited polymer films as active layers were fabricated for the preliminary investigation of their electrochromic applications.

Near-IR Electrochromism in Electrodeposited Thin Films of Cyclometalated Complexes

Homogeneous thin films of controlled thickness obtained from cyclometalated complexes of general formula [(C(∧)N)M(O(∧)N)], where M = Pd(II) or Pt(II), H(C(∧)N) = 2-phenylpyridine and, respectively, 2-thienylpyridine and H(O(∧)N) = a triphenylamine functionalized Schiff base, have been deposited by oxidative electropolymerization. The films have been electrochemically and morphologically characterized. The metallopolymeric thin films present stable reversible redox behavior and typical cauliflower-like textures in agreement with a nucleation-growth electropolymerization mechanism. However, the film growth is greatly influenced by the nature of the metal center, with a higher tendency of the Pt complexes to promote the 3D growth. Furthermore, a complete spectroelectrochemical study has been performed on electrodeposited films showing near-IR absorption in the oxidized state, high contrast ratios (up to 65%) and low response times.

Thin Film Electrodeposition of Ir(III) Cyclometallated Complexes

Novel electropolymerizable Ir(III) cyclometallated complexes have been synthesized and characterized. In these complexes the cyclometallated ligands are either 2-phenylpyridineH(PhPy) or benzothiazole-triphenylamineH(BzTh-tpa), while the Ir(III) coordination sphere is completed by a Schiff base substituted with a triphenylamine fragment. A complete electrochemical study has been conducted on all complexes, in order to verify the feasibility of electropolymerization and to elucidate the role of the specific position of the triphenylamine moiety in the molecular structure. Homogeneous thin films of Ir(III) metallopolymers have been successfully obtained through electropolymerization process.

Electrochemically fabricated electrochromic films from 4-(N-carbazolyl)triphenylamine and its dimethoxy derivative

4-(N-Carbazolyl)triphenylamine (TPACz) and its methoxy derivative MeOTPACz could be facilely fabricated into redox-active and electrochromic PTPACz polymer and (MeOTPACz)2 dimer films via electrochemical polymerization.

Tuning of resistive memory switching in electropolymerized metallopolymeric films

A diruthenium complex capped with two triphenylamine units was polymerized by electrochemical oxidation to afford metallopolymeric films with alternating diruthenium and tetraphenylbenzidine structures. The obtained thin films feature rich redox processes associated with the reduction of the bridging ligands (tetra(pyrid-2-yl)pyrazine) and the oxidation of the tetraphenylbenzidine and diruthenium segments. The sandwiched ITO/polymer film/Al electrical devices show excellent resistive memory switching with a low operational voltage, large ON/OFF current ratio (100-1000), good stability (500 cycles tested), and long retention time. In stark contrast, devices with polymeric films of a related monoruthenium complex show poor memory performance. The mechanism of the field-induced conductivity of the diruthenium polymer film is rationalized by the formation of a charge transfer state, as supported by DFT calculations.

Electrochromic polyiminocarbazolylenes with latent hydrogen bonding

Electrochromic polyiminoarylenes with carbazole units in main and side chain and thermally cleavable t-butyloxycarbonyl (boc) substituents are described. After removal of the boc groups insoluble, well adhering polymers with high contrast ratio and short switching time are obtained.

Electrosynthesis and electrochromic properties of poly(amide-triarylamine)s containing triptycene units

Redox-active and electrochromic films of poly(amide-triarylamine)s with triptycene units have been directly fabricated on the electrode surface via the electrochemical oxidative coupling of triphenylamine or carbazole units.

Facile preparation of electrochromic poly(amine–imide) films from diimide compounds with terminal triphenylamino groups via electrochemical oxidative coupling reactions

Electroactive and electrochromic poly(amine–imide) films could be directly prepared on electrodes from diimide compounds TPA6F-DI and TPASO2-DI with triphenylamino end groups by electrochemical oxidative coupling.