Dithienosilole-based all-conjugated block copolymers synthesized by a combination of quasiliving Kumada and Negishi catalyst-transfer polycondensations

Herein, we present a quasi-living Negishi-type catalyst-transfer polycondensation of a zinc–organic DTSbased monomer which provides an access to narrowly distributed poly(4,4-bis(2-ethylhexyl)dithieno[3,2-b:20,30-d]silole (PDTS) with controlled molecular weight. The synthesis of well-defined all-conjugated diblock copolymers containing a PDTS block was accomplished by a combination of Kumada and Negishi catalyst-transfer polycondensations (KCTP and NCTP, respectively). Particularly, it was shown that living P3HT chains obtained by KCTP of magnesium–organic thiophene-based monomer efficiently initiate NCTP of zinc–organic DTS-based monomer. The purity of the DTS-based monomer was found to be a crucial factor for achieving a clean chain-growth polymerization process. A combination of physico-chemical methods was used to prove the success of the block copolymerization

Enhanced photogeneration of polaron pairs in neat semicrystalline donor-acceptor copolymer films via direct excitation of interchain aggregates

We investigate the photogeneration of polaron pairs (PPs) in neat films of the semicrystalline donor–acceptor semiconducting copolymer PCPDTBT. Carefully selecting the solution-processing procedures, we obtain films with different amounts of crystallinity and interchain aggregation. We compare the photogeneration of PPs between the films by monitoring their photoinduced absorption in ultrafast pump–probe experiments, selectively exciting nonaggregated or aggregated polymer chains. The direct photoexcitation of interchain π-aggregates results in prompt (<100 fs) charge generation. Compared to the case where nonaggregated chains are excited, we find an 8-fold increase in the prompt PP to singlet-exciton ratio. We also show that highly crystalline lamellar nanostructures not containing π-stacked or any light-absorbing aggregates do not improve the efficiency of PP photogeneration. Our results show that light absorption from interchain aggregates is highly beneficial for charge photogeneration in semiconducting polymers and should be taken into account when optimizing film morphologies for photovoltaic devices

Push-pull thiophene chromophores for electro-optic applications: from 1D linear to beta-branched structures

We report the synthesis and characterization of a novel series of push-pull chromophores bearing 1D linear and beta-branched thiophenes as pi-conjugated spacers between a 2, 2, 4, 7-tetramethyl-1, 2, 3, 4-tetrahydroquinoline electron donor unit and dicyano- and tricyanovinylene electron acceptor groups. The effect of the introduction of beta-thiophenes on the linear and nonlinear (NLO) optical properties as well as electrochemical and thermal data is studied in detail by performing a comparative study between the branched and 1D linear systems. In addition, a parallel DFT computational study is used to evaluate structure-property relationships. The non-linear optical behavior of the molecules both in solution and in solid state as electro-optic (EO) films using a guest-host approach shows very promising performance for electro-optic applications with high molecular first hyperpolarizabilities (mu beta) of 4840 x 10(-48) esu and electro-optic coefficients r(33) reaching 650 pm V-1. One highlight is that the electro-optic films of the beta-branched chromophores are superior in terms of thermal stability in device operation as measured by a transmissive modified reflective Teng-Man method. This work provides guidelines for the design of improved electro-optic materials including beta-branched chromophores which could be useful for practical EO applications, where both enhanced beta and r(33) values together with chemical and thermal stability are necessary

Single waveguide silicon-organic hybrid modulator

We present a novel silicon-organic hybrid modulator based on an integrated dual-mode interferometer. The modulator offers a compact, simplified design and enhanced robustness to on-chip fluctuations of temperature compared to conventional Mach-Zehnder based systems. A prototype modulator showing a voltage dependent transmission spectrum is obtained by cladding a dual-mode waveguide in a 250 nm silicon-on-insulator technology with a customized organic electro-optic layer. Estimated phase shifts and corresponding figures of merit are discussed in this contribution. The used organic layer is based on the guest-host approach with customized donor-acceptor chromophore embedded and poled in a poly(methylmethacrylate) matrix. The presented prototype is to the best of the authors'' knowledge the first integrated single waveguide silicon-organic hybrid modulator

Autonomous Visual Detection of Defects from Battery Electrode Manufacturing

The increasing global demand for high-quality and low-cost battery electrodes poses major challenges for battery cell production. As mechanical defects on the electrode sheets have an impact on the cell performance and their lifetime, inline quality control during electrode production is of high importance. Correlation of detected defects with process parameters provides the basis for optimization of the production process and thus enables long-term reduction of reject rates, shortening of the production ramp-up phase, and maximization of equipment availability. To enable automatic detection of visually detectable defects on electrode sheets passing through the process steps at a speed of 9 m s−1, a You-Only-Look-Once architecture (YOLO architecture) for the identification of visual detectable defects on coated electrode sheets is demonstrated within this work. The ability of the quality assurance (QA) system developed herein to detect mechanical defects in real time is validated by an exemplary integration of the architecture into the electrode manufacturing process chain at the Battery Lab Factory Braunschweig

V-shaped pyranylidene/triphenylamine-based chromophores with enhanced photophysical, electrochemical and nonlinear optical properties

We report the synthesis and comprehensive study of two chromophores based on 4H-pyranylidene moiety as a part of the p-conjugated spacer. Triphenylamine (TPA) acts as donor and tricarbonitrile-based electron-accepting groups complete these V-shaped D-A-D architectures (A, acceptor; D, donor). Their electrochemical, photophysical and nonlinear optical properties are analyzed in detail by using a joint experimental and theoretical approach. The two chromophores exhibit near-infrared fluorescence, large Stokes shift, enhanced emission in tetrahydrofuran/water mixtures and good photostability. Additionally, the dimerization of triphenylamine groups to tetraphenylbenzidine (TPB) takes place upon electrochemical and chemical oxidation showing their peculiar electrochemical behavior and film formation capabilities. Interestingly, high molecular first hyperpolarizabilities and two-photon absorption cross-sections were found, highlighting their potential applications in electro-optical devices. Overall, our work demonstrates that these near-infrared (NIR) fluorescent chromophores are versatile materials with a myriad of applications ranging from optoelectronics to biological applications. © 2021 The Royal Society of Chemistry

Self-Assembly of Supramolecular Triblock Copolymer Complexes

Four different poly(tert-butoxystyrene)-b-polystyrene-b-poly(4-vinylpyridine) (PtBOS-b-PS-b-P4VP) linear triblock copolymers, with the P4VP weight fraction varying from 0.08 to 0.39, were synthesized via sequential anionic polymerization. The values of the unknown interaction parameters between styrene and tert-butoxystyrene and between tert-butoxystyrene and 4-vinylpyridine were determined from random copolymer blend miscibility studies and found to satisfy 0.031<χS,tBOS<0.034 and 0.39<χ4VP,tBOS<0.43, the latter being slightly larger than the known 0.30<χS,4VP≤0.35 value range. All triblock copolymers synthesized adopted a P4VP/PS core/shell cylindrical self-assembled morphology. From these four triblock copolymers supramolecular complexes were prepared by hydrogen bonding a stoichiometric amount of pentadecylphenol (PDP) to the P4VP blocks. Three of these complexes formed a triple lamellar ordered state with additional short length scale ordering inside the P4VP(PDP) layers. The self-assembled state of the supramolecular complex based on the triblock copolymer with the largest fraction of P4VP consisted of alternating layers of PtBOS and P4VP(PDP) layers with PS cylinders inside the latter layers. The difference in morphology between the triblock copolymers and the supramolecular complexes is due to two effects: (i) a change in effective composition and, (ii) a reduction in interfacial tension between the PS and P4VP containing domains. The small angle X-ray scattering patterns of the supramolecules systems are very temperature sensitive. A striking feature is the disappearance of the first order scattering peak of the triple lamellar state in certain temperature intervals, while the higher order peaks (including the third order) remain. This is argued to be due to the thermal sensitivity of the hydrogen bonding and thus directly related to the very nature of these systems.

Recuperação de áreas de pastagens abandonadas e degradadas através de sistemas agroflorestais na Amazônia Central.

Desenvolvimento de tecnologias para recuperar pastagens abandonadas e/ou degradadas atraves de uso de sistemas agroflorestais, como alternativa para diminuir o desmatamento e proporcionar melhorias socioeconomicas ao agricultor da regiao amazonica. Os ensaios estao sendo desenvolvidos na estacao experimetnal do CPAA. Foram implantados quatro modelos de sistemas agroflorestais em blocos ao acaso com tres repeticoes: Sistemas agrossilvipastoril-ASP1, Sistemas agrossilvipastoril-ASP2, Sistema agrossilvicultural-AS1 e Sistemas Agrossilvicultural-AS2. Os sistemas agrossilvipastoris sao formados pelo consorcio de Desmodium ovalifolium, Brachiaria humidicola e B. brizantha e linhas triplas de arvores madeireiras e leguminosas. Estao sendo avaliados a economicidade, pprodutividade, dinamica das caracteristicas fisicas e quimicas do solo. A atividade mais onerosa foi a limpeza. Os resultados preliminares indicam que os sistemas agroflorestais apresentam-se como uma tecnologia adequada ao nivel ecologico e socioeconomico da regiao, devendo ser ajustada de acordo com as potencialidades de cada local

Efficient N-Type Organic Electrochemical Transistors and Field-Effect Transistors Based on PNDI-Copolymers Bearing Fluorinated Selenophene-Vinylene-Selenophenes

n-Type organic electrochemical transistors (OECTs) and organic field-effect transistors (OFETs) are less developed than their p-type counterparts. Herein, polynaphthalenediimide (PNDI)-based copolymers bearing novel fluorinated selenophene-vinylene-selenophene (FSVS) units as efficient materials for both n-type OECTs and n-type OFETs are reported. The PNDI polymers with oligo(ethylene glycol) (EG7) side chains P(NDIEG7-FSVS), affords a high µC* of > 0.2 F cm−1 V−1 s−1, outperforming the benchmark n-type Pg4NDI-T2 and Pg4NDI-gT2 by two orders of magnitude. The deep-lying LUMO of −4.63 eV endows P(NDIEG7-FSVS) with an ultra-low threshold voltage of 0.16 V. Moreover, the conjugated polymer with octyldodecyl (OD) side chains P(NDIOD-FSVS) exhibits a surprisingly low energetic disorder with an Urbach energy of 36 meV and an ultra-low activation energy of 39 meV, resulting in high electron mobility of up to 0.32 cm2 V−1 s−1 in n-type OFETs. These results demonstrate the great potential for simultaneously achieving a lower LUMO and a tighter intermolecular packing for the next-generation efficient n-type organic electronics