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From plastic to functional elastomer by constructing Cu–S dynamic reversible bonds in CO2-based polycarbonate.

Aldehyde end-capped CO2-based polycarbonates were prepared to serve as a green platform for the construction of diverse functional polymers.

Site-specific functional polymers are generally synthesized from functionalized chain transfer agents (CTA) in the presence of catalysts. However, the poor solubility or chemical inertness of CTAs may lead to polymerizations uncontrollable. Now, this issue is addressed by proposing a strategy of designing chain-transfer-catalyst (CTC) that combines catalyst and CTA into one. The occurrence of catalytic effect naturally triggers the chain transfer process to give catalyst-labeled polymers with well-defined structures. As a proof-of-concept, cobalt(III) porphyrin catalysts with one, two and four hydroxyl groups act as efficient CTCs, giving the corresponding site-specific functional poly(propylene carbonate)s (PPC), diversifying the topology of polymers. Furthermore, porphyrin-capped PPCs with controllable Mn in the range of 1,000–16,800 g mol−1 were obtained by using monofunctional CTC (CTCOH). Moreover, different from traditional “catalyst+CTA” systems, a novel dynamic network transfer mechanism of CTCOH was proposed. This study provides a CTC strategy for the synthesis of site-specific functional polymers.

Fluorescent polymers are suffering from low electroluminescence efficiency because triplet excitons formed by electrical excitation are wasted through nonradiative pathways. Here we demonstrate the design of hyperfluorescent polymers by employing through-space charge transfer (TSCT) polystyrenes as sensitizers for triplet exciton utilization and classic fluorescent chromophores as emitters for light emission. The TSCT polystyrene sensitizers not only have high reverse intersystem crossing rates for rapid conversion of triplet excitons into singlet ones, but also possess tunable emission bands to overlap the absorption spectra of fluorescent emitters with different bandgaps, allowing efficient energy transfer from the sensitizers to emitters. The resultant hyperfluorescent polymers exhibit full-color electroluminescence with peaks expanding from 466 to 640 nm, and maximum external quantum efficiencies of 10.3–19.2%, much higher than those of control fluorescent polymers (2.0–3.6%). These findings shed light on the potential of hyperfluorescent polymers in developing high-efficiency solution-processed organic light-emitting diodes and provide new insights to overcome the electroluminescence efficiency limitation for fluorescent polymers., Hyperfluorescent polymers with high efficiency and full-color electroluminescence are developed by using through-space charge transfer polystyrenes as sensitizers for exciton utilization and fluorescent chromophores as emitters for light emission.

π-Stacked dendrimers consisting of cofacially aligned donors and acceptors are developed by introducing three dendritic teracridan donors with orthogonal configuration and three triazine acceptors in periphery of hexaphenylbenzene skeleton. The dendritic structure and orthogonal configuration of teracridan not only make their outer acridan segments approaching to acceptor in close distance, but also fix donor and acceptor in face-to-face alignment, leading to through-space charge transfer emission with thermally activated delayed fluorescence (TADF) effect. By regulating charge transfer strength via substituent effect of acceptor, emission color of the dendrimers can be tuned from blue to yellow/red region. Solution-processed two-color white organic light-emitting diodes (OLEDs) based on blue and yellow π-stacked donor-acceptor dendrimers exhibit the maximum external quantum efficiency of 20.6 % and maximum power efficiency of 58.9 lm W-1 , representing the state-of-the-art efficiency for all-TADF white OLEDs by solution process.

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.

The work discloses the use of CO2 polymer chemistry for the development of a sustainable metal anti-corrosion material. CO2-polyol, a poly(ether carbonate)diol from the telomerization of CO2 and propylene oxide catalyzed by zinc–cobalt double metal cyanide in the presence of a chain transfer agent, was used as a soft segment to prepare a waterborne cationic polyurethane dispersion (CPUD), which showed excellent hydrolysis and oxidation resistance owing to the coexistence of a hydrolysis-resistant ether unit and oxidation-resistant carbonate unit in CO2-polyol. Most importantly, to prepare a neutral CPUD dispersion compatible with an acidic conducting polyaniline, a delicately designed internal emulsifier was fabricated, in which 2,5,18,21-tetramethyl-9,14-dioxa-2,5,18,21-tetraazadocosane-7,16-diol (TDTD), combined with a sufficiently low steric hindrance tertiary amine, was used as the side chain extender (CE), with citric acid as a crosslinker. The internally crosslinked neutral CPUD was demonstrated to be compatible with a waterborne conducting polyaniline (cPANI) dispersion; the composite film obtained from the CPUD and cPANI dispersion showed a significant enhancement in barrier performance to protect against the penetration of corrosive molecules into the metal surface.

The direct ring-opening polymerization (ROP) of propylene carbonate (PC) only affords oligomers with substantial unidentified by-products, which hinders the efficient utilization of PC. Through detailed studies, for the first time, a careful mechanism involving the in situ release of propylene oxide (PO) from PC decarboxylation is proposed. Further, we report a novel strategy of copolymerization of PC/cyclic anhydrides via in situ capture of the formed intermediates. Results show that PC is successfully transformed into polyesters. Especially for the ring-opening alternating copolymerization (ROAC) of PC/phthalic anhydride (PA), a variety of advantages are manifold: i) slow-release of PO ensuring a perfectly alternating structure; ii) quantitative and fast transformation of PC; iii) visualization of polymerization process by a CO

Conjugated polyelectrolytes prepared from carbon–carbon coupling polymerization have difficulties in controlling the precision molecular weight (Mn), so that the effect of Mn on their performance r...

Cationic waterborne polyurethane (CWPU) was initially developed as a specific adhesive for anionic surface but now is ubiquitous in innovative material systems such as poly(ionic liquid)s, polyelec...

Three kinds of through-space charge transfer (TSCT) blue polymers containing non-conjugated polystyrene backbone together with spatially-separated acridan donor and oxygen-bridged triphenylboron acceptors having different substituents of tert -butyl, hydrogen and fluorine are designed and synthesized. The designed TSCT blue polymers possess photoluminescence quantum yields up to 70% in solid-state film, single-triplet energy splitting below 0.1 eV, and typical thermally activated delayed fluorescence (TADF) effect. Meanwhile, the resulting polymers exhibit aggregation-induced emission (AIE) effect with emission intensity increased by up to ∼27 folds from solution to aggregation state. By changing the substituent of acceptors to tune the charge transfer strength, blue emission with peaks from 444 to 480 nm can be realized for the resulting polymers. Solution-processed organic light-emitting diodes based on the polymers exhibit excellent device performance with Commission Internationale de L’Eclairage (CIE) coordinates of (0.16, 0.27), together with the maximum luminous efficiency of 30.7 cd A−1 and maximum external quantum efficiency of 15.0%, which is the best device efficiency for blue TADF polymers.

This work focuses on two meaningful points in green chemistry, one is providing a practical solution for CO2 transformation into a CO2 copolymer, and the other is disclosing the potential application of a CO2 copolymer as a water dispersible binder to overcome the bottleneck in heavy metal free anti-corrosion coatings. For the first point, a CO2-copolymer like CO2-polyol is synthesized from the telomerization of CO2 and propylene oxide using a zinc–cobalt double metal cyanide complex as a catalyst and terephthalic acid as a chain transfer agent. For the second point, for the past 30 years conducting polyaniline, with its unique anti-corrosion behaviour, has been regarded as a heavy metal free anti-corrosion material, but the development of a waterborne polyaniline anti-corrosion coating has encountered an impasse owing to the lack of a compatible binder. Therefore, a water borne cationic polyurethane dispersion (CPUD) was developed for this purpose, in which CO2-polyol was used as a soft segment, and 1,4-butanediol di(3-diethylamino-2-hydroxypropyl alcohol) ether was synthesized as a side-chain cationic extender. Unlike earlier acidic water borne dispersions, this water borne CPUD was near neutral, ensuring good compatibility with an aqueous conducting polyaniline dispersion, and is expected to create significant possibilities for the development of a novel generation of sustainable and eco-friendly metal anti-corrosion materials.

Through-space charge transfer dendrimers consisting of dendritic triacridan donors and oxygen-bridged triarylboron acceptors are demonstrated to exhibit deep-blue thermally activated delayed fluorescence with the state-of-the-art external quantum efficiency of 14.6% for electroluminescence by a solution process.

Cooperative catalysis is a powerful strategy in the catalytic ring-opening copolymerization of epoxides and CO2, especially for breaking through the dependence of the polymer selectivity on the tem...

Through-space charge transfer polymers (TSCT polymers) that contain a non-conjugated polystyrene backbone and spatially separated donor and acceptor units for solution-processed OLEDs with full-color and white emission is reported. By tuning the charge transfer strength between donor and acceptors with different electron-accepting ability, emission color spanning from deep blue to red can be achieved. By incorporating two kinds of donor/acceptor pairs in one polymer to create duplex through-space charge-transfer channels, blue and yellow emission can be simultaneously obtained to realize white electroluminescence from a single polymer. The TSCT polymers exhibit thermally activated delayed fluorescence effect with delayed-component lifetimes in range of 0.36-1.98 μs, and unexpected aggregation-induced emission (emission intensity enhancement of up to 117 from solution to aggregation state).

Polymer light-emitting diodes (PLEDs) based on thermally activated delayed fluorescence (TADF) emitters show great potential in developing high-efficiency solution-processed light-emitting devices ...

Four wide bandgap donor-acceptor (D-A) conjugated polymers, i.e. P-diF2T, P-TT, P-BDT and P-NDT, with bis(5-(2-decyltetradecyl)-[2,3′-bithiophen]-2′-yl)arylenes as D-units and 2-propyl-5,6-difluorobenzo[d][1,2,3]triazole (ffTAZ) as A unit were synthesized for photovoltaic applications. In P-diF2T, P-TT, P-BDT and P-NDT, 3,3′-difluoro-2,2′-bithiophene (diF2T), thieno[3,2-b]thiophene (TT), benzo[1,2-b:4,5-b']dithiophene (BDT) and naphtho[1,2-b:5,6-b']dithiophene (NDT) were used as aryl central units, respectively, to adjust the properties of the polymers. The optical bandgap is 1.83 eV for P-diF2T, 1.85 eV for P-TT, 1.90 eV for P-BDT and 2.04 eV for P-NDT. All four polymers show temperature-dependent aggregation behavior in solution, and their absorption spectra are complementary with that of non-fullerene acceptor (NFA) 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(5-hexylthiophen-2-yl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC-Th). Polymer solar cells (PSCs) based on these polymers and ITIC-Th were fabricated and characterized. Power conversion efficiencies (PCEs) higher than 7% were demonstrated for all polymers. The devices based on P-diF2T exhibited the highest PCE up to 10.08% with a high fill factor (FF) of 0.741. The good photovoltaic performance of P-diF2T is attributed to the synergies of the low-lying highest occupied molecular orbital (HOMO) energy level of the polymer and the favorable microstructures and morphology and thereby high and balanced charge carrier mobilities of the blend films. This study suggested that adjusting aromatic D units together with using alkylthiophene as side chains is an effective approach to design donor polymers for high performance PSCs based on NFA.

Two isomeric 2-hexyl substituted five-ring-fused asymmetric thienoacenes, i.e., thieno[1]benzothieno[3,2-b][1]benzothiophene (BTBTT6), in which the S atom in the terminal thiophene ring is located at different positions relative to the BTBT core, were synthesized and characterized. The syn-isomer forms bilayer “head-to-head” structures with herringbone packing modes within the layers in crystals, while the anti-isomer shows “head-to-tail” single-layer structures and sandwich-herringbone packing within the layers. The difference in packing structures involved the fact that the syn-isomer has stronger intermolecular interactions than the anti-isomer. Importantly, organic thin-film transistors (OTFTs) with near-ideal transfer and output characteristics were fabricated. Mobilities in the saturation and the linear regime (μsat and μlin) of up to 11.7 and 10.6 cm2 V−1 s−1, respectively, were achieved for the syn-isomer. This is the first report on OTFTs with both μsat and μlin above 10 cm2 V−1 s−1.

Seven diketopyrrolopyrrole (DPP)-based donor–acceptor (D–A) conjugated polymers, i.e., poly[2,5-bis(4-octadecyldocosyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-3,3′,4,4′-tetrafluoro-2,2′-bithiophene] (P4F2T-C40), poly[2,5-bis(4-octadecyldocosyl)pyrrolo[3,4-c]pyrrole-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), poly[2,5-bis(4-octadecyldocosyl)pyrrolo[3,4-c]pyrrole-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), poly[2,5-bis(4-tetradecyloctadecyl)pyrrolo[3,4-c]pyrrole-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), poly[2,5-bis(4-decyltetradecyl)pyrrolo[3,4-c]pyrrole-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), poly[2,5-bis(2-decyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-alt-5,5′-di(thiophen-2-yl)-2,2′-(E)-1,2-bis(3,4-difluorothien-2-yl)et...

In the past decade, poly(carbonate ether)polyols, or CO2-polyols, have been synthesized by the copolymerization of CO2 and propylene oxide (PO) with a double metal cyanide (DMC) catalyst in the presence of various chain transfer agents. CO2-polyols show great potential use as substitutes for polyols derived from fossil feedstock in the polyurethane industry. Brookfield viscosity tests have revealed the importance of primary hydroxyl (1° OH) content in the reactivity of CO2-polyols; in particular, the low 1° OH content of CO2-polyols severely limits their application in foam materials. Incorporation of more carbonate linkages has proven to be only moderately efficient for preparing CO2-polyols with high 1° OH content, e.g., 19F NMR spectroscopy indicates that the 1° OH content of a CO2-polyol can increase from 13% to 39% when the carbonate content in the CO2-polyol is increased from 26.1% to 80.0%. In this study, the PO end-capping route was developed using a strong Lewis acid, such as tris(pentafluorophenyl)borane (FAB) as a catalyst, and a CO2-polyol with 1° OH content of 60% was synthesized.

Quantitative transformation of CO2 can greatly elevate the sustainability impact of CO2 chemical utilization, but it is formidably challenging due to the sluggish kinetics requiring overwhelmingly excess usage of CO2. Here, we report an on demand CO2 transformation by a switch polymerization method, that is, all reactants including CO2 are fully converted without any by-product, generating tailor-made poly(ether carbonate) polyols (CO2-polyols) whose composition and chain length exactly correspond to the feed of CO2, epoxide and diacid. This is the first time for CO2 as a countable monomer which is in most cases obscurely considered as “pressure condition”. Studies on the kinetics rate law and the activation parameters of key intermediates disclose that it is the multisite cooperativity from metallic oligomer catalyst that facilitates quantitative insertion of CO2 into polymer backbone without adverse backbiting throughout the polymerization. Hence, this work not only introduces the conception of quantitative CO2 transformation, but engineers exquisite CO2-based polymer which is rarely achieved.

Through-space charge transfer polynorbornenes with fixed and controllable spatial alignment of donor and acceptor in edge-to-face/face-to-face stacking patterns are developed for achieving high-efficiency blue thermally activated delayed fluorescence (TADF). The alignment is realized by using the cis, exo-configuration of norbornene to confine donor and acceptor in close proximity, and utilizing orthogonal and dendritic structures of donors to provide either perpendicular or parallel stacking motif relative to acceptors. Compared to edge-to-face counterparts, polynorbornenes with face-to-face aligned donor and acceptor exhibit much larger oscillator strength and higher photoluminescence quantum yield. The resulting polymers exhibit deep blue (422 nm) to sky blue (482 nm) emission and TADF effect with reverse intersystem crossing rates of 0.4-5.9×106 s-1 , giving the maximum external quantum efficiency of 18.8 % for non-doped blue organic light-emitting diodes by solution process.

The utilization of CO2 as a raw material to prepare high value-added chemicals has attracted extensive attention because it is an abundant, cheap and renewable C1 source. Currently, two CO2 copolymers have been proved of industry value. One is CO2 based plastics (PPC), and the other is CO2 based polyurethane (CO2-PU), which are synthesized from copolymerization or telomerization of CO2 and propylene oxide, respectively. The 20 years’ research in Changchun Institute of Applied Chemistry witnessed the great progress in synthesis and performance improvement of CO2 based copolymers. Though challenges still exist, their bright future is predictable.

We report the design, synthesis and electroluminescent properties of three kinds of through-space charge transfer (TSCT) polymers consisting of non-conjugated polystyrene backbone, acridan donor and triarylboron acceptors having different substituents such as hydrogen (H), fluorine (F), and trifluoromethyl (CF3). Owing to the weak electron interaction between acridan donor and triarylboron acceptor through non-conjugated connection, blue emission with peaks in range of 429 nm to 483 nm can be achieved for the polymers in solid-state film, accompanied with photoluminescence quantum yields of 26–53%. The resulting TSCT polymers exhibit small ∆EST values below 0.1 eV owing to the separated HOMO and LUMO distributions, showing thermally activated delayed fluorescence with lifetimes in range of 0.19–0.98 μs. Meanwhile, the polymers show aggregation-induced emission (AIE) effect with the emission intensity increased by up to ~33 folds from solution to aggregation state. Solution-processed organic light-emitting diodes based on the polymers containing trifluoromethyl substituent exhibit promising electroluminescent performance with maximum luminous efficiency of 20.1 cd A-1 and maximum external quantum efficiency of 7.0%, indicating that they are good candidates for development of luminescent polymers.

We herein report the synthesis and characterization of four asymmetric conjugated oligomers based on polycyclic aromatics, i.e. , 2-(5-hexylselenophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-S6), 2-(5-hexylfuryl-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-F6), 2-(5-hexylselenophen-2-yl)[1]benzoselenopheno[3,2-b][1]benzoselenophene (BSBS-S6) and 2-(5-hexylfuryl-2-yl)[1]benzofuro[3,2-b][1]benzofuran (BFBF-F6), for elucidating the influence of chalcogens on molecular geometries, electronic structures, thin film microstructures and the performance of organic thin-film transistors (OTFTs). Compared to the previously reported analogue 2-(5-hexylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-T6), all four molecules have higher-lying highest occupied molecular orbital (HOMO) energy levels. BTBT-S6 and BSBS-S6 (S replaced by Se atoms) display similar mesomorphic behavior and packing motif in solid state. However, BSBS-S6 shows much poorer crystallinity. Only crystal phase was observed for BTBT-F6 and BFBF-F6 (S replaced by O atoms). These two molecules also adopt the molecular arrangements, film growth modes and film morphology distinct from BTBT-S6 and BSBS-S6. Thus, the four molecules exhibited very different OTFT performance. BTBT-S6 showed the highest mobility of 4.68 cm 2 V −1 s −1 and all other three compounds exhibited mobilites lower than 1 cm 2 V −1 s −1 .

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.

CO2 based waterborne polyurethane (CO2-WPU), especially high CO2 content one, suffered from the poor flexibility at low temperature due to high content of rigid carbonate segment. Here a microphase separation idea was proposed by introducing poly(butyl acrylate) (PBA) as soft phase to toughen CO2-WPU via an organic solvent free route, i.e., the polymerizable butyl acrylate acted as a pseudo-solvent during CO2-WPU prepolymer synthesis, it then experienced radical polymerization after formation of CO2-WPU, and finally forming a material with multi-phase structure. Benefiting from the separation of soft PBA phase and hard CO2-WPU phase in micro-size, a 368% increase in elongation at break (eb) and nearly 65 times increase in toughness at -10 °C was observed when PBA loading increased from blank to 65 wt%. As a comparison, the tensile strength (σm) and eb of the PBA/CO2-WPU blending film at room temperature was only 4.4 MPa and 383% when PBA loading was 50 wt%, while the PBA/CO2-WPU multi-phase film showed σm of 18.8 MPa and eb of 489%, respectively. The toughening effect was attributed to the more uniform micro-phase separation structure caused by molecular level inter-migration between PBA and CO2-WPU during preparation process.

Single white light-emitting polymers (SWPs) represent a high-fidelity system for generating white light emission from polymers without phase separation compared to polymer blend systems. However, their device performance so far has been limited because of the unwanted hole scattering caused by an energy-level mismatch between emitters and hosts, and the large injection barrier at the polymer/anode interface. Here, we report novel poly(arylene phosphine oxide)-based all-phosphorescent SWPs by using the combination of a high-HOMO-level blue phosphor and high-HOMO-level poly(arylene phosphine oxide) host to achieve a low turn-on voltage of 2.8 V, high external quantum efficiency of 18.0% and remarkable power efficiency of 52.1 lm W−1, which makes them the most efficient SWPs so far. This record power efficiency is realized by using the high-HOMO-level blue phosphor to eliminate the hole scattering effect and by using the high-HOMO-level polymer host to reduce the hole injection barrier. This result represents an important progress in SWPs to achieve efficiency surpassing that of the polymer blends currently used for solution-processed white organic light-emitting diodes (WOLEDs) and even comparable with that of the small molecules used for vacuum-deposited WOLEDs.

Aluminum porphyrin complexes are heavy-metal-free and soil-tolerant green catalysts for the copolymerization of CO2 and propylene oxide (PO), but they suffer from relatively poor poly(propylene carbonate) (PPC) selectivity. Herein, steric hindrance porphyrin ligand was used to enhance the PPC selectivity. Typically, a bulky anthracene-like group was incorporated into the porphyrin ring to form 5,10,15,20-tetra(1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethanoanthracen-9-yl)porphyrin, the aluminum porphyrin complex with this ligand, in combination with bis(triphenylphosphine)iminium chloride as a co-catalyst, produced completely alternate PPC. Additionally, the obtained PPC showed high regioselectivity, with a head-to-tail linkage content (HT) of 92%. Therefore, we demonstrated that introduction of bulky steric ligand into the porphyrin ring could reduce the propylene oxide homopolymerization activity leading to excellent PPC selectivity, and improve regioselectivity for the PO ring-opening during the copolymerization.

Herein, we report the synthesis and characterization of a series of [1]benzothieno[3,2-b][1]benzothiophene (BTBT)-based asymmetric conjugated molecules, that is, 2-(5-alkylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (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)[1]benzothieno[3,2-b][1]benzothiophene and 2-(5-ethylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene showed OTFT mobilities above 5 cm2 V–1 s–1. 2-(5-Hexylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene and 2-(5-heptylthiophen-2-yl)[1]benzothieno[3,2-b][1]benz...

Binder is critical component to maintain the cathode integrity in lithium-sulfur battery, but it is generally non-conductive. Here sulfuric acid doped polyaniline was successfully developed as conductive binder, which showed multifunctionality when used in Li-S battery cathode, i.e ., in addition to necessary adhesion function, it could trap polysulfide species to abate shuttling affect while provide good electrical conductivity. The unique adhesive behavior of conductive polyaniline was attributed to the sufficiently long polar chains consisting of amine salt, iminium and aromatic ring. Based on theoretical analysis, all the electrode components could be bound together by Van der Waals and electrostatic interactions even under very low polyaniline loading. Such low loading could form conductive polyaniline cobweb which helped the polyaniline binder to resist sulfur swelling while provide adequate channels for ion transportation. In an optimal condition, the polyaniline binder loading in cathode could be reduced to Ca . 2.0 wt%, and the sulfur loading in cathode increased by 11.0 wt% compared with that using common non-conductive binder. Compared with cathode employing common PVDF binder, the specific capacity using polyaniline binder increased by Ca. 104% and 74% at current density of 122 mA g −1 -sulfur and 610 mA g −1 -sulfur , respectively, which was mainly attributed to the stable conducting feature of polyaniline binder during the charging-discharging process, as reflected from low charge transfer resistance of 37 ohm for the cathode.

Two indacenodithiophene derivative bridged diketopyrrolopyrroles (DPP), i.e., 2,7-bis(2,5-bis(2-decyltetradecyl)-3,6-dioxo-4-(thiophen-2-yl)-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrol-1-yl)-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-dione (DDPP-PhCO) and 2,2′-(2,7-bis(2,5-bis(2-decyltetradecyl)-3,6-dioxo-4-(thiophen-2-yl)-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrol-1-yl)-s-indaceno[1,2-b:5,6-b′]dithiophene-4,9-diylidene)dimalononitrile (DDPP-PhCN), were developed via intramolecular Friedel–Crafts acylation and Knoevenagel condensation. A series of donor–acceptor (D–A) conjugated polymers were synthesized by Stille or direct arylation polycondensation with these two novel units as acceptors and vinyl or thiophene derivatives as donors. The polymers with DDPP-PhCO as acceptor unit exhibited optical bandgaps (Egopt) of ca. 1.2 eV and the highest occupied molecular orbital (HOMO) energy levels of ∼−5.3 eV with the difference less than 0.1 eV, and their lowest unoccupied molecular orbital (LUMO) levels were in the range o...

Three acceptor-donor-acceptor (A-D-A) conjugated oligomers, i.e., O1, O2 and O3, have been synthesized using diketopyrrolopyrrole (DPP) as an electron-acceptor unit, and naphtho[1,2-b:5,6-b’]dithiophene (NDT), anthra[1,2-b:5,6-b’]dithiophene (ADT) or dithieno[3,2-b:3’,2’-b’]naphtho[1,2-b:5,6-b’]dithiophene (DTNDT) as electron-donor unit. These oligomers exhibit identical highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, which were ca. −5.1 and −3.3 eV, respectively. Upon thermal annealing, all three oligomers formed thin films with ordered microstructures, and their organic thin film transistors (OTFTs) exhibited p-type transport behavior. The mobility was increased with an extension of the size of D-units. O3 showed the best OTFT performance with the mobility of up to 0.20 cm2·V−1·s−1. The film quality of O3 was improved by adding 1 wt% poly(methylmethacrylate) (PMMA). In consequence, the mobility of the O3-based devices was further enhanced to 0.30 cm2·V−1·s−1.

Two donor–acceptor (D–A) conjugated polymers with alkylthiophene as side chains, i.e., poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3′′′-di(2-(2-decyltetradecyl)thiophene-5-yl)-2,2′;5′,2′′;5′′,2′′′-quaterthiophene-5,5′′′-diyl)] (P-2T) and poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(2,5-bis(3-(2-decyltetradecyl)thiophene-5-yl)thiophen-2-yl)thieno[3,2-b]thiophene] (P-TT), are designed and synthesized. Both polymers exhibit temperature-sensitive aggregation in solution. Polymer solar cells (PSCs) based on them are fabricated with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor material. The devices based on P-TT deliver power conversion efficiency (PCE) up to 9.96% while no additive is used. Moreover, the photovoltaic performance of P-TT is insensitive to the polymer:PC71BM ratio and active layer thickness, and PCEs are all above 9% with the donor : acceptor (D : A) weight ratio of 1 : 1–1 : 1.8 (wt/wt) and film thickness of 200–360 nm. The high photovoltaic performance of P-TT is ascribed to its high and balanced charge carrier mobilities (4.51 × 10−3 and 3.44 × 10−3 cm2 V−1 s−1 for holes and electrons, respectively), owing to the favorable face-on packing of the conjugated backbones as well as the desired morphology of the blend films. Our study demonstrates that alkylthiophenes are one kind of promising synthon of oligothiophene based D–A conjugated polymers, which can serve as side chains for tuning the aggregation of the polymer in solution and the packing mode of the conjugated backbones in the film state.

Dendron engineering in self-host blue Ir dendrimers is reported to develop power-efficient nondoped electrophosphorescent devices for the first time, which can be operated at low voltage close to the theoretical limit (Eg/e: corresponding to the optical bandgap divided by the electron charge). With increasing dendron's HOMO energy levels from B-POCz to B-CzCz and B-CzTA, effective hole injection is favored to promote exciton formation, resulting in a significant reduction of driving voltage and improvement of power efficiency. Consequently, the nondoped device of B-CzTA achieves extremely low driving voltages of 2.7/3.4/4.4 V and record high power efficiencies of 30.3/24.4/16.3 lm W−1 at 1, 100 and 1000 cd m−2, respectively. We believe that this work will pave the way to the design of novel power-efficient self-host blue phosphorescent dendrimers used for energy-saving displays and solid-state lightings.

Four donor–acceptor (D–A) conjugated polymers (CPs), i.e., poly[(E)-1,2-bis(5-(2-hexyldecyl)-[2,3′-bithiophen]-2′-yl)ethene-alt-5,6-difluorobenzo[c][1,2,5]thiadiazole] (PTVT-T8), poly[(E)-1,2-bis(5-(2-octyldodecyl)-[2,3′-bithiophen]-2′-yl)ethene-alt-5,6-difluorobenzo[c][1,2,5]thiadiazole] (PTVT-T10), poly[(E)-1,2-bis(3-(2-hexyldecyl)thiophen-2-yl)ethene-alt-5,6-difluorobenzo[c][1,2,5]thiadiazole] (PTVT-C8) and poly[(E)-1,2-bis(3-(2-octyldodecyl)thiophen-2-yl)ethene-alt-5,6-difluorobenzo[c][1,2,5]thiadiazole] (PTVT-C10) were synthesized and characterized. Compared to PTVT-C8 and PTVT-C10, PTVT-T8 and PTVT-T10 that comprise two-dimensional (2D) conjugated D units displayed lower bandgaps, more rigid backbones, higher self-organization ability and shorter π–π stacking distances (∼3.5 A). As a result, the hole mobility of PTVT-T8 and PTVT-T10 (up to 0.42 cm2 (V s)−1) was one magnitude higher than that of PTVT-C8 and PTVT-C10 (up to 0.039 cm2 (V s)−1), as measured with organic field-effect transistors (OFETs). Polymer solar cells (PSCs) of these polymers were prepared with PC71BM as an acceptor and o-xylene as a processing solvent, and power conversion efficiencies (PCEs) up to 6.79%, 5.65%, 3.94% and 1.70% were achieved for PTVT-T8, PTVT-T10, PTVT-C8 and PTVT-C10, respectively. PTVT-T8 and PTVT-T10 exhibited photovoltaic properties superior to PTVT-C8 and PTVT-C10 owing to their high hole-mobility and the formation of ordered nano-fibrillar structures in which polymer backbones preferred face-on arrangement.

The crystallization behaviour of syndiotactic polystyrene (sPS) and benzoylated sPS (BzsPS) was investigated by POM, DSC and XRD. The results suggest β form of sPS has higher equilibrium melting temperature T m 0 and the fold surface free energy σ e than α form. With increasing benzoylation degree the growth rates and T m 0 of two forms decrease, but their T m 0 decrement is very close; the σ e of β form more increases than that of α form, the formation of α is more favourable. Upon loading trace amount of α nucleating agent PTBBNa in samples the growth rate of two forms can be strictly compared in the same melting and crystallization temperature condition, the results reveal that the growth rate of β form is faster than that of α form in sPS and BzsPS-2%. Using supercooling degree ΔT and σ e two parameters has explained the formation competition mechanism of α and β forms.

On the basis of different generation carbazole dendrons, a series of self-host yellow Ir dendrimers (Y-G0, Y-G1 and Y-G2) have been successfully synthesized and characterized in detail. It is found that the peripheral dendrons can effectively reduce the intermolecular interactions between emissive Ir cores, as verified by the increased photoluminescence quantum yields and film lifetimes. Among these dendrimers, Y-G2 bearing the second generation dendrons shows the best non-doped device performance, revealing a peak luminous efficiency of 20.2 cd/A. The value is nearly twice that of Y-G0 without any dendrons, which could be further improved to 32.1 cd/A by dispersing Y-G2 into a host matrix. We believe that this work will shed light on the development of highly efficient yellow phosphorescent dendrimers with a self-host strategy.