Short-chain fluorocarbon-based polymeric coating with excellent nonwetting ability against chemical warfare agents.

The ongoing concerns and regulations on long-chain fluorinated compounds (C8 or higher) for nonwetting coatings have driven the market to search for sustainable alternative chemistries. In this study, a copolymeric coating containing short-chain fluorinated groups was synthesized to achieve excellent nonwetting ability against hazardous chemical warfare agents (CWAs). A copolymer of 1H,1H,2H,2H-perfluorooctyl methacrylate (PFOMA) and ethylene glycol dimethacrylate (EGDMA, crosslinker) was directly coated onto a textile fabric via initiated chemical vapor deposition. The p(PFOMA-co-EGDMA) coating shows a rough-textured morphology with a bumpy, raspberry-like structure leading to high contact angles (θ water > 150° and θ dodecane = 113.8°) and a small water shedding angle (<5°). Moreover, the p(PFOMA-co-EGDMA) coating was further analysed for application in military fabrics: air permeability, tensile strength, and safety against toxic perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Outstanding nonwetting was noticeably achieved against different CWAs, including bis(2-chloroethyl)sulfide (HD), pinacolyl methylfluorophosphonate (GD), and O-ethyl S-(2-diisopropylaminoethyl)methylphosphonothioate (VX) (θ HD = 119.1°, θ GD = 117.0°, and θ VX = 104.1°). The coating retained its nano-structuration and nonwetting ability for water and n-dodecane despite being subjected to 250 cycles of Martindale abrasion and harsh chemicals (NaOH and HCl). The robustness and scalable straightforward preparation route of the coating make it an ideal approach for designing durable next-generation CWA nonwetting coatings for fabrics with favorable health and environmental properties.

High-performance and stable photoelectrochemical water splitting cell with organic-photoactive-layer-based photoanode.

Considering their superior charge-transfer characteristics, easy tenability of energy levels, and low production cost, organic semiconductors are ideal for photoelectrochemical (PEC) hydrogen production. However, organic-semiconductor-based photoelectrodes have not been extensively explored for PEC water-splitting because of their low stability in water. Herein, we report high-performance and stable organic-semiconductors photoanodes consisting of p-type polymers and n-type non-fullerene materials, which is passivated using nickel foils, GaIn eutectic, and layered double hydroxides as model materials. We achieve a photocurrent density of 15.1 mA cm-2 at 1.23 V vs. reversible hydrogen electrode (RHE) with an onset potential of 0.55 V vs. RHE and a record high half-cell solar-to-hydrogen conversion efficiency of 4.33% under AM 1.5 G solar simulated light. After conducting the stability test at 1.3 V vs. RHE for 10 h, 90% of the initial photocurrent density are retained, whereas the photoactive layer without passivation lost its activity within a few minutes.

Horizontal-, Vertical-, and Cross-Conjugated Small Molecules: Conjugated Pathway-Performance Correlations along Operation Mechanisms in Ternary Non-Fullerene Organic Solar Cells.

A family of the SM-axis series based on benzo[1,​2-​b:4,​5-​b']​dithiophene and 3-ethylrhodanine (RD) units with structurally different π-conjugation systems are synthesized as a means to understand the structure-property relationship of conjugated pathways in ternary non-fullerene organic solar cells (NF-OSCs) as a third component. The optical and electrochemical properties of the SM-axis are highly sensitive both to the functionalized direction and to the number of RD groups. Enhanced power conversion efficiencies (PCEs) of over 11% in ternary devices are obtained by incorporating optimal SM-X and SM-Y contents from PBDB-T:ITIC binary NF-OSCs, while a slightly lower PCE is observed with the addition of SM-XY. The results of in-depth studies using various characterization techniques demonstrate that working mechanisms of SM-axis-based ternary NF-OSCs are distinctly different from one another: an energy-transfer mechanism with an alloy-like model for SM-X, a charge transfer with the same model for SM-Y, and an energy transfer without such a structure for SM-XY. As extension of the scope, a SM-X-based ternary NF-OSC in the PM6:IT4F system also shows a greatly enhanced PCE of over 13%. The findings provide insights into the effects of conjugated pathways of organic semiconductors on mechanisms of ternary NF-OSCs, advancing the understanding for synthetic chemists, materials engineers, and device physicists.

Understanding of Fluorination Dependence on Electron Mobility and Stability of Naphthalenediimide-Based Polymer Transistors in Environment with 100% Relative Humidity.

A family of copolymers (P(NDIOD-T2Fx)) based on naphthalenediimide (NDI) and 2,2'-bithiophene (T2) units with different amounts of 3,3'-difluoro-2,2'-bithiophene (T2F) decoration were synthesized, characterized, and used in n-type organic field-effect transistors (OFETs). With increasing T2F content in the backbone, we observe increased melting and crystallization transitions, blue-shifted absorptions, and deeper-lying highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels, together with improved hydrophobicity. The highest electron mobility of 4.48 × 10-1 cm2 V-1 s-1 was obtained for P(NDIOD-T2F0) without a T2F unit, which is attributed to the larger domain grains and crystallites, as well as a more tightly packed and oriented crystalline structure, as evidenced from the morphological study. In contrast, P(NDIOD-T2F100) with the highest T2F content has superior air stability, showing greater than 25% electron mobility retention after 30 days in wet conditions of 100% relative humidity without encapsulation. Even P(NDIOD-T2F100) is able to operate normally after 30 min of immersion in water, which is due to the synergistic contributions from the deep HOMO/LUMO levels and improved hydrophobicity. This study advances our fundamental understanding of how the morphology/crystallinity, device performance, and device stability of n-type copolymers are tuned by incorporating different concentrations of T2F in the backbone, shedding light on an important modification for air- and water-stable n-type materials for future OFET applications.

Organic Photovoltaics with Multiple Donor-Acceptor Pairs.

Compared with conventional organic solar cells (OSCs) based on single donor-acceptor pairs, terpolymer- and ternary-based OSCs featuring multiple donor-acceptor pairs are promising strategies for enhancing the performance while maintaining an easy and simple synthetic process. Using multiple donor-acceptor pairs in the active layer, the key photovoltaic parameters (i.e., short-circuit current density, open-circuit voltage, and fill factor) governing the OSC characteristics can be simultaneously or individually improved by positive changes in light-harvesting ability, molecular energy levels, and blend morphology. Here, these three major contributions are discussed with the aim of offering in-depth insights in combined terpolymers and ternary systems. Recent exemplary cases of OSCs with multiple donor-acceptor pairs are summarized and more advanced research and perspectives for further developments in this field are highlighted.

An Ultrahigh Mobility in Isomorphic Fluorobenzo[c][1,2,5]thiadiazole-Based Polymers.

To understand the effects rendered on the relevant basic physical properties and device function by controlling the regiochemistry of the cyclopenta[1,2-b:5,4-b']dithiophene-fluorobenzo[c][1,2,5]thiadiazole polymer (hereafter referred to as the CDT-FBT polymer), two polymers, the regiorandom polymer (RA) and regioregular version (RR), respectively, are synthesized and characterized. In addition, an efficient route for synthesizing a key monomer for RR using various synthesis scope and optimizing the reaction conditions is discussed. Although RA exhibits optical, electrochemical, and morphological properties similar to RR, it shows better field-effect transistor (FET) performance. Surprisingly, by employing a capillarity-mediated sandwich-casting process on a nanogrooved substrate, an unprecedented mobility of 17.8 cm2 V-1 s-1 is obtained for RA-based FETs; this mobility value is almost twofold greater than those of the corresponding RR-based FETs. For the first time, this study challenges previously reported results in that high carrier mobility is related to the high degree of polymer order induced by the backbone regioregularity.

Stepwise heating in Stille polycondensation toward no batch-to-batch variations in polymer solar cell performance.

For a given π-conjugated polymer, the batch-to-batch variations in molecular weight (Mw) and polydispersity index (Ð) can lead to inconsistent process-dependent material properties and consequent performance variations in the device application. Using a stepwise-heating protocol in the Stille polycondensation in conjunction with optimized processing, we obtained an ultrahigh-quality PTB7 polymer having high Mw and very narrow Ð. The resulting ultrahigh-quality polymer-based solar cells demonstrate up to 9.97% power conversion efficiencies (PCEs), which is over 24% enhancement from the control devices fabricated with commercially available PTB7. Moreover, we observe almost negligible batch-to-batch variations in the overall PCE values from ultrahigh-quality polymer-based devices. The proposed stepwise polymerization demonstrates a facile and effective strategy for synthesizing high-quality semiconducting polymers that can significantly improve device yield in polymer-based solar cells, an important factor for the commercialization of organic solar cells, by mitigating device-to-device variations.

Influence of Simultaneous Tuning of Molecular Weights and Alkyl Substituents of Poly(thienoisoindigo-alt-naphthalene)s on Morphology and Change Transport Properties.

To simultaneously assess the impact of molecular weight (Mn) and alkyl substituent variations of polymers on the structural and optoelectronic properties, herein, we conduct a systematic study of a series of poly(thienoisoindigo-alt-naphthalene) (PTIIG-Np)-based polymers containing different alkyl substituents (2-hexyldecyl (HD), 2-octyldodecyl (OD), and 2-decyltetradecyl (DT) chains) and Mn's (low (L) and high (H)). All of the polymers produce almost identical energy levels, whereas their optical spectra show a clear dependence on Mn's and the alkyl substituents. Interestingly, increasing the alkyl substituent sizes of the polymers steadily increases the lamellar d-spacings (d100), ultimately leading to a densely packed lamellar structure for PTIIGHD-Np. In addition, both H-PTIIGOD-Np and H-PTIIGDT-Np exhibit larger π-stacking crystallites than the corresponding low-Mn polymers, while for PTIIGHD-Np, their size increases in the low-Mn batch. Ultimately, L-PTIIGHD-Np shows the best hole mobility of 1.87 cm2 V-1 s-1 in top-gate and bottom-contact organic field-effect transistors (OFETs) with a poly(methyl methacrylate), which is nearly 1 order of magnitude higher than other polymers tested in this study. Our results demonstrate that the simultaneous Mn and alkyl substituent engineering of the polymers can optimize their film morphology to produce high-performance OFETs.

High-Performance Furan-Containing Conjugated Polymer for Environmentally Benign Solution Processing.

Developing semiconducting polymers that exhibit both strong charge transport capability via highly ordered structures and good processability in environmentally benign solvents remains a challenge. Given that furan-based materials have better solubility in various solvents than analogous thiophene-based materials, we have synthesized and characterized furanyl-diketopyrrolopyrrole polymer (PFDPPTT-Si) together with its thienyl-diketopyrrolopyrrole-based analogue (PTDPPTT-Si) to understand subtle changes induced by the use of furan instead of thiophene units. PTDPPTT-Si films processed in common chlorinated solvent exhibit a higher hole mobility (3.57 cm2 V-1 s-1) than PFDPPTT-Si films (2.40 cm2 V-1 s-1) under the same conditions; this greater hole mobility is a result of tightly aggregated π-stacking structures in PTDPPTT-Si. By contrast, because of its enhanced solubility, PFDPPTT-Si using chlorine-free solution processing results in a device with higher mobility (as high as 1.87 cm2 V-1 s-1) compared to that of the corresponding device fabricated using PTDPPTT-Si. This mobility of 1.87 cm2 V-1 s-1 represents the highest performances among furan-containing polymers reported to the best of our knowledge for nonchlorinated solvents. Our study demonstrates an important step toward environmentally compatible electronics, and we expect the results of our study to reinvigorate the furan-containing semiconductors field.

Amphiphilic Graft Copolymers as a Versatile Binder for Various Electrodes of High-Performance Lithium-Ion Batteries.

It is known that grafting one polymer onto another polymer backbone is a powerful strategy capable of combining dual benefits from each parent polymer. Thus amphiphilic graft copolymer precursors (poly(vinylidene difluoride)-graft-poly(tert-butylacrylate) (PVDF-g-PtBA)) have been developed via atom transfer radical polymerization, and demonstrated its outstanding properties as a promising binder for high-performance lithium-ion battery (LIB) by using in situ pyrolytic transformation of PtBA to poly(acrylic acid) segments. In addition to its superior mechanical properties and accommodation capability of volume expansion, the Si anode with PVDF-g-PtBA exhibits the excellent charge and discharge capacities of 2672 and 2958 mAh g(-1) with the capacity retention of 84% after 50 cycles. More meaningfully, the graft copolymer binder shows good operating characteristics in both LiN0.5 M1.5 O4 cathode and neural graphite anode, respectively. By containing such diverse features, a graft copolymer-loaded LiN0.5 M1.5 O4 /Si-NG full cell has been successfully achieved, which delivers energy density as high as 546 Wh kg(-1) with cycle retention of ≈70% after 50 cycles (1 C). For the first time, this work sheds new light on the unique nature of the graft copolymer binders in LIB application, which will provide a practical solution for volume expansion and low efficiency problems, leading to a high-energy-density lithium-ion chemistry.

Siloxane-based hybrid semiconducting polymers prepared by fluoride-mediated suzuki polymerization.

Siloxane-containing materials are a large and important class of organic-inorganic hybrids. In this report, a practical variation of the Suzuki polymerization to generate semiconducting polymeric hybrids based on siloxane units, which proceeds under essentially nonbasic conditions, is presented. This method generates solution-processable poly(diketopyrrolopyrrole-alt-benzothiadiazole) (PDPPBT-Si) consisting of the hybrid siloxane substituents, which could not be made using conventional methods. PDPPBT-Si exhibits excellent ambipolar transistor performance with well-balanced hole and electron FET mobilities. The siloxane-containing DPP-thiophene polymer classes (PDPP3T-Si and PDPP4T-Si), synthesized by this method, exhibit high hole mobility of up to 1.29 cm(2) V(-1) s(-1) . This synthetic approach should provide access to a variety of novel siloxane-containing conjugated semiconductor classes by using a variety of aryldihalides and aryldiboronic acids/esters.

Fluorinated benzothiadiazole (BT) groups as a powerful unit for high-performance electron-transporting polymers.

Over the past few years, one of the most remarkable advances in the field of polymer solar cells (PSCs) has been the development of fluorinated 2,1,3-benzothiadiazole (BT)-based polymers that lack the solid working principles of previous designs, but boost the power conversion efficiency. To assess a rich data set for the influence of the fluorinated BT units on the charge-transport characteristics in organic field-effect transistors (OFETs), we synthesized two new polymers (PDPP-FBT and PDPP-2FBT) incorporating diketopyrrolopyrrole (DPP) and either single- or double-fluorinated BT and thoroughly investigated them via a range of techniques. Unlike the small differences in the absorption properties of PDPP-FBT and its nonfluorinated analogue (PDPP-BT), the introduction of doubly fluorinated BT into the polymer backbone induces a noticeable change in its optical profiles and energy levels, which results in a slightly wider bandgap and deeper HOMO for PDPP-2FBT, relative to the others. Grazing incidence X-ray diffraction (GIXD) analysis reveals that both fluorinated polymer films have long-range orders along the out-of-plane direction, and π-π stacking in the in-plane direction, implying semicrystalline lamellar structures with edge-on orientations in the solid state. Thanks to the strong intermolecular interactions and highly electron-deficient π-systems driven by the inclusion of F atoms, the polymers exhibit electron mobilities of up to 0.42 and 0.30 cm2 V(-1) s(-1) for PDPP-FBT and PDPP-2FBT, respectively, while maintaining hole mobilities higher than 0.1 cm2 V(-1) s(-1). Our results highlight that the use of fluorinated BT blocks in the polymers is a promising molecular design strategy for improving electron transporting performance without sacrificing their original hole mobility values.

Synthesis of PCDTBT-based fluorinated polymers for high open-circuit voltage in organic photovoltaics: towards an understanding of relationships between polymer energy levels engineering and ideal morphology control.

The introduction of fluorine (F) atoms onto conjugated polymer backbone has verified to be an effective way to enhance the overall performance of polymer-based bulk-heterojunction (BHJ) solar cells, but the underlying working principles are not yet fully uncovered. As our attempt to further understand the impact of F, herein we have reported two novel fluorinated analogues of PCDTBT, namely, PCDTFBT (1F) and PCDT2FBT (2F), through inclusion of either one or two F atoms into the benzothiadiazole (BT) unit of the polymer backbone and the characterization of their physical properties, especially their performance in solar cells. Together with a profound effect of fluorination on the optical property, nature of charge transport, and molecular organization, F atoms are effective in lowering both the HOMO and LUMO levels of the polymers without a large change in the energy bandgaps. PCDTFBT-based BHJ solar cell shows a power conversion efficiency (PCE) of 3.96 % with high open-circuit voltage (VOC) of 0.95 V, mainly due to the deep HOMO level (-5.54 eV). To the best of our knowledge, the resulting VOC is comparable to the record VOC values in single junction devices. Furthermore, to our delight, the best PCDTFBT-based device, prepared using 2 % v/v diphenyl ether (DPE) additive, reaches the PCE of 4.29 %. On the other hand, doubly-fluorinated polymer PCDT2FBT shows the only moderate PCE of 2.07 % with a decrease in VOC (0.88 V), in spite of the further lowering of the HOMO level (-5.67 eV) with raising the number of F atoms. Thus, our results highlight that an improvement in efficiency by tuning the energy levels of the polymers by means of molecular design can be expected only if their truly optimized morphologies with fullerene in BHJ systems are materialized.

Protective effects of Paeonia lactiflora pall on hydrogen peroxide-induced apoptosis in PC12 cells.

This study was conducted to examine the antioxidative and neuroprotective effects of Paeonia lactiflora pall (PLE). Total phenolic content of PLE was 89.65 mg of gallic acid equivalent per gram of PLE. IC(50) values for reducing power, hydrogen peroxide scavenging activity, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were 297.57, 3.33, and 32.74 microg, respectively. The protective effect of PLE against H(2)O(2)-induced oxidative damage to PC12 cells was investigated by an 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) reduction assay and lactate dehydrogenase (LDH) release assay. After 2 h of cell exposure to 0.5 mM H(2)O(2), a marked reduction in cell survival was observed. However, this reduction was significantly prevented by 10-100 microg/ml of PLE. H(2)O(2) also induced severe apoptosis of the PC12 cells, which was indicated by a flow cytometric analysis. Interestingly, the H(2)O(2)-stressed PC12 cells that had been incubated with PLE had greatly suppressed apoptosis. The results suggest that PLE could be a candidate for a new antioxidant against neuronal diseases.