An iridescent chameleon‐like material that can change its colors under different circumstances is always desired in color‐on‐demand applications. Herein, a strategy based on trichromacy and the ...dynamically tunable fluorescence resonance energy transfer (FRET) process to design and prepare these chameleon‐like fluorescent materials is proposed. A set of trichromic (red, green, and blue), solid fluorescent materials are synthesized by covalently attaching spiropyran, fluorescein, and pyrene onto cellulose chains independently. After simply mixing them together, a full range of color is realized. The chameleon‐like nature of these materials is based on the dynamic tunable FRET process between donors (green and blue) and acceptors (red) in which the energy transfer efficiency can be finely tuned by irradiation. Ultimately, the reversible and nonlinear regulation of fluorescence properties, including color and intensity, is achieved on a timescale recognizable by the naked eye. Benefited by the excellent processability inherited from the cellulose derivatives, the as‐prepared materials are feasibly transformed into different forms. Particularly, a fluorescent ink with the complicated fluorescent input–output dependence suggests more than a proof‐of‐concept; indeed, it suggests a unique method of information encryption, security printing, and dynamic anticounterfeiting.
An iridescent chameleon‐like material is constructed from natural cellulose to achieve a dynamic full‐color emission.
A diketopyrrolopyrrole‐based conjugated polymer, PDPP‐4FTVT, which exhibits ambipolar transport behavior in air with hole and electron mobilities up to 3.40 and 5.86 cm2 V−1 s−1, respectively, is ...synthesized via direct arylation polycondensation. Incorporation of F‐atoms in β‐positions of thiophene rings dramatically improves the efficiency of direct arylation polycondensation.
Graphene-wrapped polyaniline nanofibers were prepared by assembly of negatively charged graphene oxide with positively charged aqueous dispersible polyaniline nanofibers in an aqueous dispersion, ...followed by the reduction of the graphene oxide. The hybrid material with a graphene oxide loading of 9.1wt.% displayed a high specific capacitance of over 250Fg−1 in a 1M Et4N+·BF4−/propylene carbonate electrolyte, a 39.7% increase compared with pristine polyaniline nanofibers. A significant improvement in long-term cycle life was also realized. The hybrid exhibited an initial specific capacitance of 236Fg−1, which remained as high as 173.3Fg−1 over 1000cycles, or a 26.3% decrease, much better than that for pure polyaniline nanofibers. An asymmetric supercapacitor based on this hybrid material and activated carbon was assembled. An energy density of 19.5Whkg−1 at a power density of 738.95Wkg−1 was obtained for the cell under an operating voltage window of 2V.
Three highly rigid and planar low‐bandgap conjugated polymers comprising alternate isoindigo and dithienocarbazole groups are synthesized for the fabrication of high performance polymer solar cells. ...Power conversion efficiencies of up to 7.2% for conventional devices and 8.2% for inverted devices are demonstrated.
The one‐step synthesis of well‐defined CO2‐based diblock copolymers was achieved by simultaneous ring‐opening copolymerization (ROCOP) of CO2/epoxides and RAFT polymerization of vinyl monomers using ...a trithiocarbonate compound bearing a carboxylic group (TTC‐COOH) as the bifunctional chain transfer agent (CTA). The double chain‐transfer effect allows for independent and precise control over the molecular weight of the two blocks and ensures narrow polydispersities of the resultant block copolymers (1.09–1.14). Notably, an unusual axial group exchange reaction between the aluminum porphyrin catalyst and TTC‐COOH impedes the formation of homopolycarbonates. By taking advantage of the RAFT technique, it is able to meet the stringent demand for functionality control to well expand the application scopes of CO2‐based polycarbonates.
The one‐step synthesis of CO2‐based block copolymers with completely alternating polycarbonate segments was achieved by simultaneous ring opening copolymerization of CO2/epoxides and RAFT polymerization of vinyl monomers. A double chain‐transfer effect ensures narrow polydispersities, and a ligand exchange reaction impedes the formation of homopolycarbonates.
Boron (B)- and sulfur (S)-doped polycyclic aromatic hydrocarbons (PAHs) are developed as a novel kind of multiple resonance emitters for ultrapure blue thermally activated delayed fluorescence (TADF) ...polymers with narrowband electroluminescence. The combination of electron-deficient B atom and electron-rich S atom in PAH can form an intramolecular push-pull electronic system in a rigid aromatic framework, leading to reduced singlet-triplet energy splitting and limited structure relaxation of excited states. The critical roles of S atom in determining emission properties with respect to the oxygen analogues are in two aspects: (i) reducing energy bandgap to shift emission from human-eye-insensitive ultraviolet zone to blue region, and (ii) promoting reverse intersystem crossing process by heavy-atom effect to activate TADF effect. The resulting polymer containing B,S-doped PAH as emitter and acridan as host exhibits efficient blue electroluminescence at 458 nm with small full-width at half-maximum of 31 nm, representing the first example for ultrapure TADF polymer with narrowband electroluminescence.
Herein, we report the synthesis and characterization of a series of 1benzothieno3,2-b1benzothiophene (BTBT)-based asymmetric conjugated molecules, that is, ...2-(5-alkylthiophen-2-yl)1benzothieno3,2-b1benzothiophene (BTBT-Tn, in which T and n represent thiophene and the number of carbons in the alkyl group, respectively). All of the molecules with n ≥ 4 show mesomorphism and display smectic A, smectic B (n = 4), or smectic E (n > 4) phases and then crystalline phases in succession upon cooling from the isotropic state. Alkyl chain length has a noticeable influence on the microstructures of vacuum-deposited films and therefore on the performance of the organic thin-film transistors (OTFTs). All molecules except for 2-(thiophen-2-yl)1benzothieno3,2-b1benzothiophene and 2-(5-ethylthiophen-2-yl)1benzothieno3,2-b1benzothiophene showed OTFT mobilities above 5 cm2 V–1 s–1. 2-(5-Hexylthiophen-2-yl)1benzothieno3,2-b1benzothiophene and 2-(5-heptylthiophen-2-yl)1benzothieno3,2-b1benzothiophene showed the greatest OTFT performance with reliable hole mobilities (μ) up to 10.5 cm2 V–1 s–1 because they formed highly ordered and homogeneous films with diminished grain boundaries.
Seven diketopyrrolopyrrole (DPP)-based donor–acceptor (D–A) conjugated polymers, i.e., ...poly2,5-bis(4-octadecyldocosyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-3,3′,4,4′-tetrafluoro-2,2′-bithiophene (P4F2T-C40), poly2,5-bis(4-octadecyldocosyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-1,2-bis(3,4-difluorothiophen-2-yl)ethyne (P4FTAT-C40), poly2,5-bis(4-octadecyldocosyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene (P4FTVT-C40), poly2,5-bis(4-tetradecyloctadecyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene (P4FTVT-C32), poly2,5-bis(4-decyltetradecyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene (P4FTVT-C24), poly2,5-bis(2-decyldodecyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene (P4FTVT-C22), and poly2,5-bis(2-decyltetradecyl)pyrrolo3,4-cpyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)ethene (P4FTVT-C10C12), were synthesized by direct arylation polycondensation (DArP) with multi-fluorinated thiophene derivatives 3,3′,4,4′-tetrafluoro-2,2′-bithiophene (4F2T), (E)-1,2-bis(3,4-difluorothien-2-yl)ethene (4FTVT), or 1,2-bis(3,4-difluorothiophen-2-yl) acetylene (4FTAT) as the comonomer. The structures of the multi-fluorinated thiophene derivatives have a noticeable influence on the optical properties and self-assembly properties of the polymers. Compared to P4F2T-C40, P4FTVT-C40 showed an ∼30 nm red-shift while P4FTAT-C40 exhibited an ∼60 nm blue-shift of the absorption spectrum. Top-gate and bottom-contact (TGBC) organic field-effect transistors (OFETs) of all the polymers exhibited ambipolar transport behavior. The devices based on P4FTAT-C40 displayed poor device performance since its film was almost amorphous. In contrast, the polymer based on 4FTVT with the same alkyl side chains delivered much better device performance due to its crystalline nature, favorable molecular orientations, and appropriate film morphology. With optimized side chains, P4FTVT-C32 exhibited the highest hole (μh) and electron mobilities (μe) of ca. 2.6 and ca. 8.0 cm2 V–1 s–1 in air, respectively.
A series of solution‐processible 2,2′‐dimethyl‐biphenyl cored dendrimers, namely G1MP, G2MP, and G3MP, is designed and synthesized by tuning the generation of periphery carbazole dendron. The ...resulting dendrimers all show excellent solubility in common organic solvents, and their high‐quality thin films can be formed via spin‐coating with a root‐mean‐square roughness in the range of 0.38–0.54 nm. G3MP, which contains the third‐generation carbazole dendron, has the greatest potential among those made here as an ideal universal host for multicolored triplet emitters. G3MP exhibits good thermal stability, with a glass transition temperature of 368 °C, a triplet energy as high as 2.85 eV enough to prevent the loss of triplet excitons, and suitable HOMO/LUMO levels of –5.30/–2.11 eV to facilitate both hole and electron injection and transport. When using G3MP as the host, highly efficient deep‐blue, blue, green, and red phosphorescent organic light‐emitting diodes (PhOLEDs) are successfully demonstrated, revealing a maximum luminous efficiency up to 18.2, 28.2, 54.0, and 12.7 cd A–1 with the corresponding Commission Internationale de L'Eclairage (CIE) coordinates of (0.15, 0.23), (0.15, 0.35), (0.38, 0.59), and (0.64, 0.34), respectively. The state‐of‐art performance indicates that dendritic hosts have a favorable prospect of applications in solution‐processed white PhOLEDs and full‐color displays.
A high triplet energy and suitable HOMO/LUMO levels for effective charge injection are realized in dendrimer G3MP with a third‐generation carbazole dendron, due to a small exchange energy of 0.33 eV. Therefore, G3MP can be utilized as a high‐performance universal host for a wide color range of phosphors from deep blue to red.
Interfacial thermal conductance (ITC) receives enormous consideration because of its significance in determining thermal performance of hybrid materials, such as polymer based nanocomposites. In this ...study, the ITC between sapphire and polystyrene (PS) was systematically investigated by time domain thermoreflectance (TDTR) method. Silane based self-assembled monolayers (SAMs) with varying end groups, -NH2, -Cl, -SH and -H, were introduced into sapphire/PS interface, and their effects on ITC were investigated. The ITC was found to be enhanced up by a factor of 7 through functionalizing the sapphire surface with SAM, which ends with a chloride group (-Cl). The results show that the enhancement of the thermal transport across the SAM-functionalized interface comes from both strong covalent bonding between sapphire and silane-based SAM, and the high compatibility between the SAM and PS. Among the SAMs studied in this work, we found that the ITC almost linearly depends on solubility parameters, which could be the dominant factor influencing on the ITC compared with wettability and adhesion. The SAMs serve as an intermediate layer that bridges the sapphire and PS. Such a feature can be applied to ceramic-polymer immiscible interfaces by functionalizing the ceramic surface with molecules that are miscible with the polymer materials. This research provides guidance on the design of critical-heat transfer materials such as composites and nanofluids for thermal management.
