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The poor operational stability of non-fullerene electron acceptor (NFA) organic solar cells (OSCs) currently limits their commercial application. While previous studies have primarily focused on the degradation of the NFA component, we also consider here the electron donor material. We examine the stability of three representative donor polymers, PM6, D18, and PTQ10, paired with the benchmark NFA, Y6. After light soaking PM6 and D18 in air, we find an enhanced conversion of singlet excitons into trapped interchain polaron pairs on sub-100 femtosecond timescales. This process outcompetes electron transfer to Y6, significantly reducing the charge generation yield. However, this pathway is absent in PTQ10. We identify twisting in the benzo[1,2-b:4,5-b′]dithiophene (BDT)-thiophene motif shared by PM6 and D18 as the cause. By contrast, PTQ10 does not contain this structural motif and has improved stability. Thus, we show that the donor polymer can be a weak link for OSC stability, which must be addressed collectively with the NFA.

Organic semiconductors combine flexible tailoring of their optoelectronic properties by synthetic means with strong light-matter coupling, which is advantageous for organic electronic device applications. Although spatially selective deposition has been demonstrated, lateral patterning of organic films with simultaneous control of molecular and crystalline orientation is lacking as traditional lithography is not applicable. Here, a new patterning approach based on surface-localized F-centers (halide vacancies) generated by electron irradiation of alkali halides is presented, which allows structural control of molecular adlayers. Combining optical and atomic force microscopy, X-ray diffraction, and density functional theory (DFT) calculations, it is shown that dinaphthothienothiophene (DNTT) molecules adopt an upright orientation on pristine KCl surfaces, while the F-centers stabilize a recumbent orientation, and that these orientations are maintained in thicker films. This specific nucleation results also in different crystallographic morphologies, namely, densely packed islands and jagged fibers, each epitaxially aligned on the KCl surface. Spatially selective surface irradiation can also be used to create patterns of F-centers and thus laterally patterned DNTT films, which can be further transferred to any (including elastomer) substrate due to the water solubility of the alkali halide growth templates.

An in-depth investigation of the oxyanionic ring-opening copolymerization of propylene oxide (PO) and allyl glydicyl ether (AGE) from benzyl alcohol (BnOH) activated with potassium acetate (KOAc) complexed by 18-crown-6 ether (18C6) is described. We demonstrate that the KOAc/18C6 complex is an efficient and benign catalytic system to promote copolymerization of both oxirane monomers, leading well-defined polyethers with varied co-monomer content and low dispersity values (ƉM < 1.20). Kinetic analysis confirmed the controlled nature of the (co)polymerization process, and the determination of reactivity ratios by 1H NMR spectroscopy revealed a quasi-alternating copolymerization profile, according to the Fineman-Ross method. These results highlight the great potential of 18C6/KOAc-mediated copolymerization process for the design of highly sought quasi-alternating copolymer platforms, not accessible with the common polymerization systems.

This study is focused on the Y6 electron acceptor to assess the impact of elongating the inner side chain from 8 to 12 carbon atoms by combining DFT calculations, UV-visible spectroscopy, atomic force microscopy analysis and device characterization.

The design of semiconducting polymers with optimal charge transport characteristics has been at the crux of scientific research during the recent decades. While increase in crystalline order and planar conjugated backbones were demonstrated to be the key to success, they are not always mandatory. Sometimes, the charge carrier mobility can be enhanced by selecting conjugated backbones that are resilient to thermal fluctuations, despite leading to poor structural order. Herein, by coupling all-atom molecular dynamics simulations, electronic structure calculations, and kinetic Monte Carlo charge transport simulations, we demonstrate that the charge carrier mobility in amorphous donor-acceptor conjugated polymers is controlled by the density and quality of close-contact points between the chains and that the latter varies with the size of the donor block and the resulting alkyl side-chain density. We show an application of this strategy to the high-mobility poly(indacenodithiophene-alt-benzothiadiazole) (IDTBT) and poly(dithiopheneindenofluorene-alt-benzothiadiazole) (TIFBT) copolymers.

The synthesis of a novel polyhedral oligomeric silsesquioxane functionalized with eight rigid and directional terpyridine-based arms (Ter-POSS) was successfully achieved via a Sonogashira reaction. The POSS based ligand was extensively characterized using different techniques including 1H, 13C and 29Si NMR as well as UV-Vis and fluorescence spectroscopies. The assembly of these nano-caged units in the presence of different transition metal ions (Fe2+, Zn2+ and Cu2+) as well as of a cation from the lanthanides (Eu3+) was investigated using absorption and emission spectroscopies. The final materials display an evident emission in different regions of the visible spectrum as a function of the cation employed. Additional insights into the structural organization of Ter-POSS in the presence of metal cations were obtained via molecular mechanics and molecular dynamics simulations. The polymeric material resulting from the complexation with europium displays a white light emission ascribed to the presence of combined contributions from the blue, green and red regions. The final self-assembled organizations display an increased quantum yield with the highest value (29.6%) obtained in the presence of Zn2+. Moreover, the white-light emitting europium-based nanostructure exhibits one of the highest quantum yields reported in the literature for similar solids.

Electronic structure calculations unveil structure-property relationships in doped polymers: dopants inserted in the alkyl chains are stronger electron acceptors than those in conjugated backbones, leading to integer charge transfer complexes.

We study by scanning thermal microscopy the nanoscale thermal conductance of films (40-400 nm thick) of [1]benzothieno[3,2-b][1]benzothiophene (BTBT) and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT-C8). We demonstrate that the out-of-plane thermal conductivity is significant along the interlayer direction, larger for BTBT (0.63 ± 0.12 W m-1 K-1) compared to C8-BTBT-C8 (0.25 ± 0.13 W m-1 K-1). These results are supported by molecular dynamics calculations (approach to equilibrium molecular dynamics method) performed on the corresponding molecular crystals. The calculations point to significant thermal conductivity (3D-like) values along the 3 crystalline directions, with anisotropy factors between the crystalline directions below 1.8 for BTBT and below 2.8 for C8-BTBT-C8, in deep contrast with the charge transport properties featuring a two-dimensional character for these materials. In agreement with the experiments, the calculations yield larger values in BTBT compared to C8-BTBT-C8 (0.6-1.3 W m-1 K-1versus 0.3-0.7 W m-1 K-1, respectively). The weak thickness dependence of the nanoscale thermal resistance is in agreement with a simple analytical model. This journal is, M. G., D. G., S. L. and D. V. thank the ANR for financial support (ANR-16-CE05-0029). Y. G. is thankful to the Belgian National Fund for Scientific Research (FNRS) for financial support through research projects BTBT (# 2.4565.11), Phasetrans (# T.0058.14), Pi-Fast (# T.0072.18), 2D to 3D (# 30489208), and DIFFRA (# U.G001.19). Financial supports from the French Community of Belgian (ARC # 20061) is also acknowledged. G. S. acknowledges postdoctoral fellowship support from the FNRS. The work in the Laboratory for Chemistry of Novel Materials was supported by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifique de Belgique (F.R.S.-FNRS) under grant # 2.5020.11. J.C. and A.V. are FNRS research fellows.

Doped organic semiconductors are critical to emerging device applications, including thermoelectrics, bioelectronics, and neuromorphic computing devices. It is commonly assumed that low conductivities in these materials result primarily from charge trapping by the Coulomb potentials of the dopant counterions. Here, we present a combined experimental and theoretical study rebutting this belief. Using a newly developed doping technique based on ion exchange, we prepare highly doped films with several counterions of varying size and shape and characterize their carrier density, electrical conductivity, and paracrystalline disorder. In this uniquely large data set composed of several classes of high-mobility conjugated polymers, each doped with at least five different ions, we find electrical conductivity to be strongly correlated with paracrystalline disorder but poorly correlated with ionic size, suggesting that Coulomb traps do not limit transport. A general model for interacting electrons in highly doped polymers is proposed and carefully parametrized against atomistic calculations, enabling the calculation of electrical conductivity within the framework of transient localization theory. Theoretical calculations are in excellent agreement with experimental data, providing insights into the disorder-limited nature of charge transport and suggesting new strategies to further improve conductivities.

Peptoids are attractive substitutes for peptides in several research areas, especially when they adopt a helical structure. The chain-size evolution of the secondary structure of the widely studied (S)-N-1-phenylethyl peptoids is here analyzed by means of the ion mobility mass spectrometry technique increasingly used as a powerful analytical tool and is further supported by theoretical modeling. We conclude that the helical shape of the peptoids prevailing in solution is lost in the gas phase by the need to screen the positive charge borne by the peptoid even though the collisional cross sections are close to the values expected for helical systems. We further illustrate that trend line analyses predicting molecular shapes from fits of the size evolution of cross sections can be very misleading since they critically depend on the range of polymerization degrees under study.

Mass spectrometric techniques and more particularly collision-induced dissociation (CID) experiments represent a powerful method for the determination of the primary sequence of (bio)molecules. However, the knowledge of the ion fragmentation patterns say the dissociation reaction mechanisms is a prerequisite to reconstitute the sequence based on fragment ions. Previous papers proposed that protonated peptoids dissociate following an oxazolone-ring mechanism starting from the O-protonation species and leading to high mass Y sequence ions. Here we revisit this backbone cleavage mechanism by performing CID and ion mobility experiments, together with computational chemistry, on tailor-made peptoids. We demonstrated that the B/Y cleavages of collisionally activated O-protonated peptoids must involve the amide nitrogen protonated structures as the dissociating species, mimicking the CID behavior of protonated peptides. Upon the nucleophilic attack of the oxygen atom of the N-terminal adjacent carbonyl group on the carbonyl carbon atom of the protonated amide, the peptoid ions directly dissociate to form an ion-neutral complex associating an oxazolone ion to the neutral truncated peptoid residue. Dissociation of the ion/neutral complex predominantly produces Y ions due to the high proton affinity of the secondary amide function characteristic of truncated peptoids. Whereas the production of Yx ions from acetylated peptoids also involves the B/Y pathway, the observation of abundant Yx ions from non-acetylated peptoid ions is shown in the present study to arise from an A1-Yx mechanism. The consecutive and competitive characters of the A1-Yx and the B/Y mechanisms are also investigated by drift time-aligned CID experiments.

Funder: Consortium des Équipements de Calcul Intensif, Funder: The Leverhulme Trust, While the charge transport properties of organic semiconductors have been extensively studied over the recent years, the field of organics‐based thermoelectrics is still limited by a lack of experimental data on thermal transport and of understanding of the associated structure–property relationships. To fill this gap, a comprehensive experimental and theoretical investigation of the lattice thermal conductivity in polycrystalline thin films of dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (Cn‐DNTT‐Cn with n = 0, 8) semiconductors is reported. Strikingly, thermal conductivity appears to be much more isotropic than charge transport, which is confined to the 2D molecular layers. A direct comparison between experimental measurements (3ω–Völklein method) and theoretical estimations (approach‐to‐equilibrium molecular dynamics (AEMD) method) indicates that the in‐plane thermal conductivity is strongly reduced in the presence of the long terminal alkyl chains. This evolution can be rationalized by the strong localization of the intermolecular vibrational modes in C8‐DNTT‐C8 in comparison to unsubstituted DNTT cores, as evidenced by a vibrational mode analysis. Combined with the enhanced charge transport properties of alkylated DNTT systems, this opens the possibility to decouple electron and phonon transport in these materials, which provides great potential for enhancing the thermoelectric figure of merit ZT.

Polymeric semiconductors exhibit exceptionally long spin lifetimes, and recently observed micrometre spin diffusion lengths in conjugated polymers demonstrate the potential for organic spintronics devices. Weak spin–orbit and hyperfine interactions lie at the origin of their long spin lifetimes, but the coupling mechanism of a spin to its environment remains elusive. Here, we present a systematic study of polaron spin lifetimes in field-effect transistors with high-mobility conjugated polymers as an active layer. We demonstrate how spin relaxation is governed by the charges’ hopping motion at low temperatures, whereas an Elliott–Yafet-like relaxation due to a transient localization of the carrier wavefunctions is responsible for spin relaxation at high temperatures. In this regime, charge, spin and structural dynamics are intimately related and depend sensitively on the local conformation of polymer backbones and the crystalline packing of the polymer chains. The long spin lifetimes observed in polymeric semiconductors hold promise for potential applications. A careful study untangles the main mechanism behind them.

Despite offering robust mechanical properties, polymer networks suffer from a lack of recyclability, reshaping, and healability. Designing stiff and remendable polymer networks that can repair under mild conditions remains a challenge to extend their field of applications. Herein, we describe a simple approach to design a nonisocyanate-based polyurethane network featuring multiresponsiveness (to humidity and temperature) and outstanding healing properties, as obtained by combining iminoboronate and boroxine chemistry. In spite of the presence of abundant dynamic bonds, the network has a high stiffness (Young's modulus of 551 MPa) and tensile strength (11 MPa). C?N iminoboronate and B-O boroxine exchange reactions at high temperature enable efficient network recycling over multiple cycles without compromising its properties. Owing to these features, 3D objects could be designed and printed. The present approach provides excellent sustainable and high-performance substitution to conventional polyurethane networks requiring the use of toxic isocyanates., SCOPUS: ar.j, info:eu-repo/semantics/published

Peptoids constitute an emergent class of synthetic biocompatible macromolecules that are best described as polymers of N-substituted glycines. Peptides and peptoids are regioisomers with the side chains appended in peptoids to the nitrogen atoms rather than to the α-carbon atoms as in peptides. Peptide sequencing now takes great advantage of collision-induced dissociation experiments, based on the elucidation of the decomposition pathways of protonated peptides. In contrast, data on peptoid ion decompositions are to date scarcely present in the literature. Upon CID, protonated peptoids were recently shown to mostly dissociate by cleavages at the backbone amide bonds yielding B- and Y-fragment ions. In addition, the loss of the side-chain group and/or the formation of the side-chain fragment ion are common reactions for peptoids containing protonated N-α-aromatic side chain. In the present paper, we submitted protonated tailor-made peptoids to (energy-resolved) collision-induced dissociation experiments to investigate the side-chain loss reaction mechanisms. We also used orthogonal methods, such as quantum chemistry, ion mobility spectrometry and infrared photodissociation spectroscopy to establish the structures of the fragment ions. We ended up with different mechanistic scenarios consistent with the nature of the fragment ions and the kinetic energy dependence of decomposition reactions. Our mechanistic proposals associate the proton mobile model, proton bound dimer intermediacy and concerted rearrangement reactions.

Recent studies point to an additional stability of metal-complexed functionalized hydrocarbon chains. This additional stabilization is suggested to arise from a bidentate complexation of the metal cation with both the functional group and aliphatic chain, leading to more folded structures. In the present work, this issue is verified for silver complexed alkylamines by tandem mass spectrometry and ion mobility experiments combined with quantum-chemical calculations. Upon increasing the length of the hydrocarbon chains, the alkylamine/silver complexes undergo a structural transition to reach a folded structure in which the silver cation interacts with both the amine group and hydrogen atoms located at the chain end. This folding is further examined by monitoring the loss of AgH upon collision-induced dissociation experiments performed on alkylamines with different chain lengths. Ion mobility experiments performed on the fragment ions indicate that the removal of the silver cation induces the unfolding of the chain.

Resonant X-ray diffraction exploits energy-dependent changes in X-ray scattering across an elemental absorption edge to provide additional information about the organization of atoms within the unit cell. Here, we demonstrate the utility of performing resonant X-ray diffraction at multiple absorption edges to provide complementary information about atomic positions and bond orientation. These experiments are achieved through the chlorination of a well-studied naphthalene diimide bithiophene copolymer, P(NDI2OD-T2), to produce P(NDI2OD-T2Cl2), enabling measurements at sulfur and chlorine K-edges. Strong modulation of the diffraction intensity is observed at both edges but with significant differences in the observed diffraction anisotropy. These differences in diffraction anisotropy arise due to differences in the orientation of sulfur and chlorine bonds within the unit cell. Simulations of the supramolecular organization of P(NDI2OD-T2Cl2) have also been performed, with P(NDI2OD-T2Cl2) showing a similar lowest energy packing geometry to unchlorinated P(NDI2OD-T2). Comparing the simulated unit cells with the experimental results, we find that the experimental results are best explained by a mixture of anti and syn conformers in thin film samples of P(NDI2OD-T2Cl2). This observation is in line with the smaller energy barrier computed at the quantum chemical level between the two conformers providing a higher flexibility of the conjugated backbones.

Charge transport in organic semiconductors is notoriously extremely sensitive to the presence of disorder, both internal and external (i.e. related to the interactions with the dielectric layer), especially for n-type materials. Internal dynamic disorder stems from large thermal fluctuations both in intermolecular transfer integrals and (molecular) site energies in weakly interacting van der Waals solids and sources transient localization of the charge carriers. The molecular vibrations that drive transient localization typically operate at low-frequency (< a-few-hundred cm-1), which renders it difficult to assess them experimentally. Hitherto, this has prevented the identification of clear molecular design rules to control and reduce dynamic disorder. In addition, the disorder can also be external, being controlled by the gate insulator dielectric properties. Here we report on a comprehensive study of charge transport in two closely related n-type molecular organic semiconductors using a combination of temperature-dependent inelastic neutron scattering and photoelectron spectroscopy corroborated by electrical measurements, theory and simulations. We provide unambiguous evidence that ad hoc molecular design enables to free the electron charge carriers from both internal and external disorder to ultimately reach band-like electron transport., arXiv admin note: text overlap with arXiv:1909.05344

Funding: C.Li thanks the Prof. & Mrs. Purdie Bequests Scholarship and AstraZeneca for a PhD Studentship. We are grateful to the Engineering and Physical Sciences Research Council of the UK (EPSRC) for financial support (grants EP/R035164/1 and EP/P010482/1). We acknowledge the EPSRC UK National Mass Spectrometry Facility at Swansea University for mass spectrometry analysis. The work in Mons was supported by the European Commission / Région Wallonne (FEDER –BIORGEL project), the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds National de la Recherche Scientifique (F.R.S.-FNRS) under Grant No. 2.5020.11 as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under Grant Agreement n1117545, and FRS-FNRS. The synthesis and photophysical study of two dinuclear copper(I) complexes bearing a 2-(1H-imidazol-2-yl)pyrimidine bridging ligand are described. The tetrahedral coordination sphere of each copper center is completed through the use of a bulky bis(phosphine) ligand, either DPEphos or Xantphos. Temperature-dependent photophysical studies demonstrated emission through a combination of phosphorescence and thermally activated delayed fluorescence for both complexes, and an intense emission (ΦPL = 46%) was observed for a crystalline sample of one of the complexes reported. The photophysics of these two complexes is very sensitive to the environment. Two pseudopolymorphs of one of the dinuclear complexes were isolated, with distinct photophysics. The emission color of the crystals can be changed by grinding, and the differences in their photophysics before and after grinding are discussed. Postprint

The charge transport–limiting factors in conjugated polymers without single-bond linkages in the backbone have been identified., We investigate the charge transport physics of a previously unidentified class of electron-deficient conjugated polymers that do not contain any single bonds linking monomer units along the backbone but only double-bond linkages. Such polymers would be expected to behave as rigid rods, but little is known about their actual chain conformations and electronic structure. Here, we present a detailed study of the structural and charge transport properties of a family of four such polymers. By adopting a copolymer design, we achieve high electron mobilities up to 0.5 cm2 V−1 s−1. Field-induced electron spin resonance measurements of charge dynamics provide evidence for relatively slow hopping over, however, long distances. Our work provides important insights into the factors that limit charge transport in this unique class of polymers and allows us to identify molecular design strategies for achieving even higher levels of performance.

Recent advances in molecular dynamics (MD) simulations have made it possible to examine the behavior of large charged droplets that contain analytes such as proteins or polymers, thereby providing insights into electrospray ionization (ESI) mechanisms. In the present study, we use this approach to investigate the release of polylactide (PLA) ions from water/acetonitrile ESI droplets. We found that cationized gaseous PLA ions can be formed via various competing pathways. Some MD runs showed extrusion and subsequent separation of polymer chains from the droplet, as envisioned by the chain ejection model (CEM). On other occasions the PLA chains remained inside the droplets and were released after solvent evaporation to dryness, consistent with the charge residue model (CRM). Following their release from ESI droplets, the nascent gaseous PLA ions were subjected to structural relaxation for several μs in vacuo. The MD conformations generated in this way for various PLA charge states compared favorably to experimental results obtained by ion mobility spectrometry-mass spectrometry (IMS-MS). The structures of all PLA ions evolved during relaxation in the gas phase. However, some macroion species retained features that resembled their nascent structures. For this subset of ions, the IMS-MS response appears to be strongly correlated with the ESI release mechanism (CEM vs. CRM). The former favored extended structures, whereas the latter preferentially generated compact conformers.

The two-dimensional shape information yielded by ion mobility-mass spectrometry (IM-MS), usually reported as collision cross section (CCS), is often correlated to the underlying three-dimensional structures of the ions through computational chemistry. Here, we used theoretical approaches based on molecular mechanics (MM), molecular dynamics (MD), and density functional theory (DFT) to elucidate the structures of sodiated poly(ethoxy phosphate) polymer ions at different degrees of polymerization (DP) for three different charge states (1+, 2+, and 3+) by comparing computational results to experimentally obtained CCS values. From the calculated structures, we extract several key interaction distances which merge in clusters for all screened charge states and DPs, independent of the three-dimensional structures and the polymer ion structural rearrangements. These distances were also used to extract the minimum coordination numbers in poly(ethoxy phosphate) and to describe the preferred coordination geometries. When sodiated and protonated polymer ions are compared, the experimental CCS evolutions differ at small DP values and merge at higher DPs. We investigated in more depth this difference for two selected species, namely, [PEtP

One major goal in medical imaging is the elaboration of more efficient contrast agents (CAs). Those agents need to be optimized for the detection of affected tissues such as cancers or tumors while decreasing the injected quantity of agents. The paramagnetic contrast agents containing fluorine atoms can be used for both proton and fluorine magnetic resonance imaging (MRI), and they open the possibility of simultaneously mapping the anatomy using 1H MRI and accurately locating the agents using 19F MRI. One of the challenges in this domain is to synthesize molecules containing several chemically equivalent fluorine atoms with relatively short relaxation times to allow the recording of 19F MR images in good conditions. With that aim, we propose to prepare a CA containing a paramagnetic center and nine chemically equivalent fluorine atoms using a cycloaddition reaction between two building blocks. These fluorinated contrast agents are characterized by 19F NMR, showing differences in the fluorine relaxation times T1 and T2 depending on the lanthanide ion. To complement the experimental results, molecular dynamics simulations are performed to shed light on the 3D-structure of the molecules in order to estimate the distance between the lanthanide ion and the fluorine atoms.

We compare two small π-conjugated donor-bridge-acceptor organic molecules differing mainly in the number of thiophene rings in their bridging motifs (1 ring in 1; 2 rings in 2) with the aim of rationalizing the origin of the enhancement in the singlet exciton diffusion coefficient and length of 1 with respect to 2. By combining force field molecular dynamics and micro electrostatic schemes with time-dependent density functional theory and kinetic Monte Carlo simulations, we dissect the nature of the lowest electronic excitations in amorphous thin films of these molecules and model the transport of singlet excitons across their broadly disordered energy landscapes. In addition to a longer excited-state lifetime associated with a more pronounced intramolecular charge-transfer character, our calculations reveal that singlet excitons in 1 are capable of funneling through long-distance hopping percolation pathways, presumably as a result of the less anisotropic shape of the molecule, which favours long-range 3D transport.

Self-healing polymeric materials that can spontaneously repair in a perpetual manner are highly appealing to address safety and restoration issues in different key applications. Usually built from reversible moieties that require to be activated using, for example, temperature, light, or pH changes, most of these self-healing materials rely on energy-demanding processes and/or external interventions to promote self-healing. In this work, we propose to exploit rapid dynamic exchanges between urea-based moieties and moisture as an alternative to promote local and spontaneous healing responses to damage using atmospheric moisture as an external stimulus. Non-hygroscopic urea-based polyurethanes with repetitive moisture-induced healing abilities at different degrees of humidity were thus designed through coupling reactions with non-hygroscopic polypropylene glycol and urea moieties. As supported by density functional theory (DFT) calculations coupled to local FTIR experimental studies, we furthermore established that the healing mechanism is ultimately related to the formation of water-urea clusters. Obviously, this work represents a platform for designing more advanced spontaneous self-healing materials beyond the present study, which hold promise for use in a wide range of technological applications.

Molecular doping—the use of redox‐active small molecules as dopants for organic semiconductors—has seen a surge in research interest driven by emerging applications in sensing, bioelectronics, and thermoelectrics. However, molecular doping carries with it several intrinsic problems stemming directly from the redox‐active character of these materials. A recent breakthrough was a doping technique based on ion‐exchange, which separates the redox and charge compensation steps of the doping process. Here, the equilibrium and kinetics of ion exchange doping in a model system, poly(2,5‐bis(3‐alkylthiophen‐2‐yl)thieno(3,2‐b)thiophene) (PBTTT) doped with FeCl3 and an ionic liquid, is studied, reaching conductivities in excess of 1000 S cm−1 and ion exchange efficiencies above 99%. Several factors that enable such high performance, including the choice of acetonitrile as the doping solvent, which largely eliminates electrolyte association effects and dramatically increases the doping strength of FeCl3, are demonstrated. In this high ion exchange efficiency regime, a simple connection between electrochemical doping and ion exchange is illustrated, and it is shown that the performance and stability of highly doped PBTTT is ultimately limited by intrinsically poor stability at high redox potential.

Introduction Antibiotic detection has become a major issue in many fields such as water analysis, food control, health, etc. Besides the immediate dangers, the spread of antibiotics everywhere provokes the phenomenon of bacterial resistance which, on the long run, will cause health issues. Indeed, the excessive use of antibiotics allows the bacteria to mutate and thus develop resistance, requiring the development of new compounds. This work aims to develop and characterize a sensing material to detect multiple antibiotics in liquid phase using various methods. The idea is to conceive low power sensors or even disposable sensors. Therefore, sensors should be low cost and compatible for mass production. The most interesting sensitive materials appear to be Molecularly Imprinted Polymers (also called MIP) using conductive polymers [1],[2]. Synthesis of the MIP Polypyrrole (PPy) is chosen as conductive polymer to be molecularly imprinted. Pyrrole (Py) is used as the cross-linker and pyrrole-3-carboxylic acid as the functional monomer, to obtain chemical interactions between the polymer and the target molecule (also called “template”). The synthesis is performed in-situ (also called bulk polymerization) in aqueous media by mixing the target molecule, the functional monomer and the cross-linker with the oxidizer, ammonium persulfate (APS), while the pH value is set to around 2.2, well below the template pKa to allow better interactions between monomers and the template. During oxidative polymerization, the temperature is kept at 30 °C, for 2 hours. The polymer is then deposited on the substrates used to get the sensor. The next step, so-called extraction, consists in removing the template from the polymer. It is performed by using a solution of methanol and HCl (9:1) wherein substrates are immersed for 2 hours [3]. Then, substrates are stored in PBS (phosphate buffered saline) solution before being tested. Non-Imprinted Polymers (NIP) are also synthetized following the same steps, except that the template is not present during the synthesis. Measurement methods Polymerization has been performed on various substrates allowing to use multiple sensing methods to explore as much paths as possible. Sensitive materials have been deposited on chemoresistive plastic IDE (InterDigitated Electrodes) to perform EIS measurements (Electrochemical Impedance Spectroscopy), on quartz crystal microbalance to perform mass measurements and on glass slide to perform optical absorbance measurements, as shown on Fig.1. Results and Conclusions After the extraction step carried out on the various substrates, detection is performed by adding the target antibiotic into the PBS solution. Fig. 2 shows impedance measurements revealing that this parameter grows nearly linearly as soon as we add a dozen ppb of the antibiotic. Fig.3 shows that using the same measurement method, the NIP does nearly not react when we add the template, which means that the imprinting is functional and significantly increases the performance of the sensor. Similar results were obtained with spectrophotometry NIR (Near InfraRed)measurements on Fig. 4 and Fig. 5. This method exhibits some limitations with a saturation above 50 ppb. Beside these practical measurements, modeling has been performed by MD (Molecular Dynamic) to simulate 2 steps of the practical process: the pre-polymerization assembly and the extraction step. EIS fittings have also been achieved on the experimental results. An example of these fittings is presented on Fig 6, where it is possible to observe the good correlation between the fitting and the experimental curves, at 0 ppb for sensitive layers synthesized at various pH values. The utilization of fitting and modeling software aims to provide a better understanding of the physical phenomena occurring during the experiments. In conclusion, the sensors were found to be able to detect concentrations of approximately 15 ppb and are close to the detection limits of conventional methods (10 ppb). In addition, they have proven their specificity to the target molecule by showing no reaction when exposed to the usual interferents. We showed that the MIP is suitable for both impedimetric sensors as well as for optical sensors (optical fibers or dipsticks for instance). References [1] S. A.Piletsky, N. W.Turner, P. Laitenberger, Molecularly imprinted polymers in clinical diagnostics – future potential and existing problems, Medical Engineering & Physics , 28 (2006), 971-977. doi:10.1016/j.medengphy.2006.05.004 [2] M. Díaz-Bao, R. Barreiro, J. M. Miranda, A. Cepeda et P. Regal, Fast HPLC-MS/MS Method for Determining Penicillin Antibiotics in Infant Formulas Using Molecularly Imprinted Solid-Phase Extraction, Journal of Analytical Methods in Chemistry, 2015 (2015). doi: 10.1155/2015/959675 [3] J. L. Urraca, A. J. Hall, M. C. Moreno‐Bondi, B. Sellergren, A Stoichiometric Molecularly Imprinted Polymer for the Class‐Selective Recognition of Antibiotics in Aqueous Media, Angewandte Chemie, 118 (2006), 5282-5285. doi: 10.1002/ange.200601636 Figure 1

In the field of polymer characterization, the use of ion mobility mass spectrometry (IMMS) remains mainly devoted to the temporal separation of cationized oligomers according to their charge states, molecular masses and macromolecular architectures in order to probe the presence of different structures. When analyzing multiply charged polymer ions by IMMS, the most striking feature is the observation of breaking points in the evolution of the average collision cross sections with the number of monomer units. Those breaking points are associated to the folding of the polymer chain around the cationizing agents. Here, we scrutinize the shape of the arrival time distribution (ATD) of polylactide ions and associate the broadening as well as the loss of symmetry of the ATD signals to the coexistence of different populations of ions attributed to the transition from opened to folded stable structures. The observation of distinct distributions reveals the absence of folded/extended structure interconversion on the ion mobility time scale (1-10 ms) and then on the lifetime of ions within the mass spectrometer at room temperature. In order to obtain information on the possible interconversion between the different observed populations upon ion activation, we performed IM-IM-MS experiments (tandem ion mobility measurements). To do so, mobility-selected ions were activated by collisions before a second mobility measurement. Interestingly, the conversion by collisional activation from a globular structure into a (partially) extended structure, i.e. the gas phase unfolding of the ions, was not observed in the energetic regime available with the used experimental setup. The absence of folded/extended interconversion, even upon collisional activation, points to the fact that the polylactide ions are 'frozen' in their specific 3D structure during the desolvation/ionization electrospray processes. Copyright © 2017 John Wiley & Sons, Ltd.

Organic semiconductors are usually polycyclic aromatic hydrocarbons and their analogs containing heteroatom substitution. Bioinspired materials chemistry of organic electronics promises new charge transport mechanism and specific molecular recognition with biomolecules. We discover organic semiconductors from deoxyribonucleic acid topoisomerase inhibitors, featuring conjugated backbone decorated with hydrogen-bonding moieties distinct from common organic semiconductors. Using ellipticine as a model compound, we find that hydrogen bonds not only guide polymorph assembly, but are also critical to forming efficient charge transport pathways along π−conjugated planes when at a low dihedral angle by shortening the end-to-end distance of adjacent π planes. In the π−π stacking and hydrogen-bonding directions, the intrinsic, short-range hole mobilities reach as high as 6.5 cm2V−1s−1 and 4.2 cm2V−1s−1 measured by microwave conductivity, and the long-range apparent hole mobilities are up to 1.3 × 10–3 cm2V−1s−1 and 0.4 × 10–3 cm2V−1s−1 measured in field-effect transistors. We further demonstrate printed transistor devices and chemical sensors as potential applications., To unlock the potential of biological semiconductors for printed flexible electronics, experimental evidence that reveals the material’s charge transport mechanism is required. Here, the authors report the charge transport mechanism in hydrogen-bonded DNA topoisomerase inhibitors.

Increasing the crystallinity of thin films in concert with the planarization of the conjugated backbones has long been considered as the key for success in the design of polymer materials with optimized charge transport properties. Recently, this general belief had to be revisited with the emergence of a new class of disordered or even seemingly amorphous donor− acceptor conjugated polymers that exhibit charge mobilities larger than 1 cm2 V−1 s −1 . By combining all-atom molecular dynamics simulations to electronic structure calculations on three representative polymers, we demonstrate that high crystallinity and planar conjugated backbones are not mandatory to reach low-energetic-disorder materials. It is rather the resilience to thermal fluctuations of the torsions along the conjugated backbones within and between structural domains and the bulkiness of the alkyl side chains that control the energy landscape.

Mass spectrometric techniques and more particularly collision-induced dissociation (CID) experiments represent a powerful method for the determination of the primary sequence of (bio)molecules. However, the knowledge of the ion fragmentation patterns say the dissociation reaction mechanisms is a prerequisite to reconstitute the sequence based on fragment ions. Previous papers proposed that protonated peptoids dissociate following an oxazolone-ring mechanism starting from the O-protonation species and leading to high mass Y sequence ions. Here we revisit this backbone cleavage mechanism by performing CID and ion mobility experiments, together with computational chemistry, on tailor-made peptoids. We demonstrated that the B/Y cleavages of collisionally activated O-protonated peptoids must involve the amide nitrogen protonated structures as the dissociating species, mimicking the CID behavior of protonated peptides. Upon the nucleophilic attack of the oxygen atom of the N-terminal adjacent carbonyl group on the carbonyl carbon atom of the protonated amide, the peptoid ions directly dissociate to form an ion-neutral complex associating an oxazolone ion to the neutral truncated peptoid residue. Dissociation of the ion/neutral complex predominantly produces Y ions due to the high proton affinity of the secondary amide function characteristic of truncated peptoids. Whereas the production of Y

The molecular properties of [1]benzothieno[3,2-b][1]benzothiophene (BTBT) are vulnerable to structural modifications, which in turn are determined by the functionalization of the backbone. Hence versatile synthetic strategies are needed to discover the properties of this molecule. To address this, we have attempted heteroatom (oxygen) functionalization of BTBT by a concise and easily scalable synthesis. Fourfold hydroxy-substituted BTBT is the key intermediate, from which the compounds 2,3,7,8-bis(ethylenedioxy)-[1]benzothieno[3,2-b][1]benzothiophene and 2,3,7,8-bis(methylenedioxy)-[1]benzothieno[3,2-b][1]benzothiophene are synthesized. The difference in ether functionalities on the BTBT scaffold influences the ionisation potential values substantially. The crystal structure reveals the transformation of the herringbone motif in bare BTBT towards π-stacked columns in the newly synthesized derivatives. The results are further justified by the simulated HOMO levels of the model compound., SCOPUS: ar.j, info:eu-repo/semantics/published

Neutral green-emitting four-coordinate Cu(I) complexes with general formula POPCu(NN), where POP = bis[2-(diphenylphosphino)phenyl]ether and NN = substituted 2-pyridine-1,2,4-triazole ligands, were synthesized. The crystal structures of (POPCuMeCN)(+)(PF6)(-) (1), POPCuPhPtp (2a, PhPtp = 2-(5-phenyl-2H-[1,2,4]triazol-3-yl)-pyridine), and POPCu(3,5-2FPhPtp) (2d, 3,5-2FPhPtp = 2-(5-(3,5-difluorophenyl)-2H-1,2,4-triazol-3-yl)pyridine) were determined by single-crystal X-ray diffraction analysis. The electronic and photophysical properties of the complexes were examined by UV-vis, steady-state, and time-resolved spectroscopy. At room temperature, weak emission was observed in solution, while in the solid state, all complexes exhibit intense green emission with quantum yield up to 0.54. The electronic and photophysical properties were further supported by calculation performed at the (time-dependent) density functional theory level. One of the complexes was also tested as dopant in electroluminescent devices.

Host-guest complexes are formed by the creation of multiple noncovalent bonds between a large molecule (the host) and smaller molecule(s) or ion(s) (the guest(s)). Ion-mobility separation coupled with mass spectrometry nowadays represents an ideal tool to assess whether the host-guest complexes, when transferred to the gas phase upon electrospray ionization, possess an exclusion or inclusion nature. Nevertheless, the influence of the solution conditions on the nature of the observed gas-phase ions is often not considered. In the specific case of inclusion complexes, kinetic considerations must be taken into account beside thermodynamics; the guest ingression within the host cavity can be characterized by slow kinetics, which makes the complexation reaction kinetically driven on the timescale of the experiment. This is particularly the case for the cucurbituril family of macrocyclic host molecules. Herein, we selected para-phenylenediamine and cucurbit[6]uril as a model system to demonstrate, by means of ion mobility and collision-induced dissociation measurements, that the inclusion/exclusion topology ratio varies as a function of the equilibration time in solution prior to the electrospray process.

Efficient conjugated polymer optoelectronic devices benefit from concomitantly high luminescence and high charge carrier mobility. This is difficult to achieve, as interchain interactions, which are needed to ensure efficient charge transport, tend also to reduce radiative recombination and lead to solid-state quenching effects. Many studies detail strategies for reducing these interactions to increase luminescence, or modifying chain packing motifs to improve percolation charge transport; however achieving these properties together has proved elusive. Here, we show that properly designed amorphous donor-alt-acceptor conjugated polymers can circumvent this problem; combining a tuneable energy gap, fast radiative recombination rates and luminescence quantum efficiencies >15% with high carrier mobilities exceeding 2.4 cm2/Vs. We use photoluminescence from exciton states pinned to close-crossing points to study the interplay between mobility and luminescence. These materials show promise towards realising advanced optoelectronic devices based on conjugated polymers, including electrically-driven polymer lasers., Designing conjugated polymers with high charge carrier mobility and fluorescence quantum efficiency, though attractive for optoelectronics, remains challenging. Here, the authors report a strategy for designing donor-acceptor copolymers whose optoelectronic properties exceed the state-of-the-art.