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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.

International audience; Understanding the surface properties of hybrid perovskite materials is a key aspect to improve not only the interface properties in photovoltaic cells but also the stability against moisture degradation. In this work, we study the local electronic properties of two series of CH 3 NH 3 PbI 3 perovskite films by atomic force microscopybased methods. We correlate nanoscale features such as the local surface potential (as measured by Kelvin probe force microscopy) to the current response (as measured by conductive atomic force microscopy). CH 3 NH 3 PbI 3 perovskites made using lead acetate as a precursor result in films with high purity and crystallinity and also result in heterogeneous local electrical properties, attributed to variations in the density of surface states. In contrast, when using lead iodide as a precursor, the perovskite surface exhibits a uniform distribution of surface states. This work also aims to understand the early stages of water-induced degradation at the surface of those films. Through high-precision exposure to small amounts of water vapor, we observe a higher stability for surfaces prepared with lead iodide precursors. More importantly, each precursor-based fabrication route is associated with either nor p-type behavior of the films. These characteristics are determined by the type of surface states, which also and eventually preside over stability. This work should help discriminate between perovskite synthesis routes and improve their stability in photovoltaic cell applications.

The rapid growth of wearables has created a demand for lightweight, elastic and conformal energy harvesting and storage devices. The conducting polymer poly(3,4-ethylenedioxythiophene) has shown great promise for thermoelectric generators, however, the thick layers of pristine poly(3,4-ethylenedioxythiophene) required for effective energy harvesting are too hard and brittle for seamless integration into wearables. Poly(3,4-ethylenedioxythiophene)-elastomer composites have been developed to improve its mechanical properties, although so far without simultaneously achieving softness, high electrical conductivity, and stretchability. Here we report an aqueously processed poly(3,4-ethylenedioxythiophene)-polyurethane-ionic liquid composite, which combines high conductivity (>140 S cm−1) with superior stretchability (>600%), elasticity, and low Young’s modulus (, Though deformable thermoelectric materials are desirable for integrating thermoelectric devices into wearable electronics, typical thermoelectric materials are too brittle for practical application. Here, the authors report a high-performance elastic composite for stretchable thermoelectric modules.

International audience; We have investigated the potential as an OLED emitter of a spiro compound with phosphine substituents initially designed as a host layer for triplet emitters. This is motivated by the fact that the spiro architecture is expected to reduce the detrimental impact of intermolecular interactions, thus allowing for the use of a single-component layer. Moreover, theoretical calculations suggest that this compound displays all features required for a thermally-assisted delayed fluorescence (TADF) behavior. The photophysical properties of the compound in solution are extremely unusual, as illustrated in particular by a dual emission band with relative intensities strongly depending on the experimental conditions. Although no TADF behavior is evidenced in OLED devices, the compound unexpectedly generates a white light signal, which is interpreted as the result of the formation of both intramolecular and intermolecular (exciplex) charge-transfer states.

This work aims at presenting an innovative method for tailoring the morphology of functionalized plasma polymer films (PPF). The approach is based on the formation of a plasma polymer bilayer system in which the two layers differ by their chemical composition and cross-linking degree. As a case study, propanethiol-based plasma polymer films have been investigated. As revealed by a much higher S/C ratio than in the propanethiol precursor (i.e. 0.83 vs 0.33), it has been demonstrated that the bottom layer contains a large fraction of trapped sulfur-based molecules (e.g. H2S). When further covered by a denser PPF formed at higher energetic conditions, a three-dimensional morphological reorganization takes place giving rise to the micro/nano structuration of the organic material. The shape, the dimensions as well as the density of the generated structures are found to depend on the thickness of both coatings involved in the bilayer structure, offering a great flexibility for surface engineering. Annealing experiments unambiguously confirm the major role played by the sulfur-based trapped molecules for inducing the reshaping process. The whole set of data clearly paves the way for the development of an innovative approach for finely tailoring the morphology of functionalized PPF at the micro/nano scale.

We have used atomistic simulations to study the network topology and the thermomechanical properties of the methyl-4,4-bis-[6-(3-phenyl-3,4-dihydro-2H-1,3-benzoxazine)]pentanoate based system (MDP-a), in comparison with commercially available bisphenol-A based benzoxazine (Ba-a). In the first part of the work, we focus on the effect of the transesterification reaction of the ester group of the MDP-a molecule on the overall properties of the crosslinked resin. Remarkably, this additional crosslink site shifts the Tg of the MDP-a thermoset by 116 °C as compared to the same resin generated with a conventional tetra-functional crosslinking scheme. The rapid increase of the thermomechanical stability is shown to be mostly related to the volume shrinkage of the thermoset upon curing. In the second part of this study, we report on the effect of carbon nanotubes (CNTs) on the properties of both BA-a and MDP-a polybenzoxazines, in particular on the glass transition temperature. We find that the addition of CNTs has a negligible impact on the Tg of the BA-a resin, whereas it induces a surge of 45 °C in Tg for the MDP-a nanocomposite. A detailed analysis suggests that the change of the thermomechanical stability of the CNT-nanocomposites is a result of the balance between different structural variations (free volume, crosslink and hydrogen bond densities, chain mobility) and the polymer/CNT interfacial energy.

Phosphonium-based polythiophene conjugated polyelectrolytes (CPEs) with three different counterions (dodecylsulfate, octylsulfate and perfluorooctane sulfonate) are synthesized to determine how the nature of the counterion affects the thermal properties, the self-assembly in thin films and the performance as the cathode interfacial layer in polymer solar cells (PSCs). The counterion has a significant effect on the thermal properties of the CPEs, affecting both their glass transition and crystalline behaviour. Grazing-incidence wide-angle X-ray scattering studies also indicate that changing the nature of the counterion influences the microstructural organization in thin films (face-onversusedge-on orientation). The affinity of the CPEs with the underlying photoactive layer in PSCs is highly correlated with the counterion species. Finally, in addition to an increase of the power conversion efficiency ofca15% when using these CPEs as cathode interfacial layers in PSCs, a higher device stability is noted, compared to a reference device with a calcium interlayer. (c) 2020 Society of Industrial Chemistry This work was supported by the CNRS and the Universite de Montpellier. This work was also supported in part by the Science Foundation Ireland under grant no. 12/IP/1608. Research in Mons is supported by FNRS-FRFC (2Dto3D project - EOS programme) and Region Wallonne (OPTI2MAT excellence programme). The University of Mons and Hasselt University co-authors are grateful for financial support by the Science Policy Office of the Belgian Federal Government (BELSPO; PAI/IAP 7/05). JK is a postdoctoral fellow of the Research Foundation - Flanders (FWO Vlaanderen). NVdB thanks the Vrije Universiteit Brussel for a post-doctoral grant. The HINT COST action MP1202 and French-Irish programme 'Hubert Curien Ulysses' (31998ZF) are also acknowledged for support. This research has also been supported by the European Commission under the 7th Framework Programme through the 'Research Infrastructures' action of the 'Capacities' programme (contract no. CP-CSA_INFRA-2008-1.1.1 Number 226507-NM13). We further thank the Diamond Light Source for beamtime at the I07 beamline (experiment SI13868) and TA Instruments for the RHC equipment. Clement, S (corresponding author), Univ Montpellier, ENSCM, CNRS, ICGM, Montpellier, France. sebastien.clement1@umontpellier.fr

A small percentage of an impurity was shown, via scanning tunneling microscopy, to drastically change the on-surface self-assembly behavior of an aromatic tetracarboxylic acid, by initiating the nucleation and growth of a different polymorph. Molecular modelling simulations were used to shed further light onto the dopant-controlled assembly behaviour. ispartof: CHEMICAL COMMUNICATIONS vol:57 issue:12 pages:1454-1457 ispartof: location:England status: published

New solid polymer electrolytes are of particular interest for next-generation high-energy batteries since they can overcome the limited voltage window of conventional polyether-based electrolytes. Herein, a flame-retardant phosphorus-containing polymer, poly(dimethyl(methacryloyloxy)methyl phosphonate) (PMAPC1) is introduced as a promising polymer matrix. Free-standing membranes are easily obtained by mixing PMAPC1 with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and a small amount of acetonitrile (AN). LiTFSI/AN mixed aggregates are formed that act as plasticizers and enable ionic conductivities up to 1.6 × 10-3 S cm-1 at 100 °C. The high content of LiTFSI used in our electrolytes leads to the formation of a stable LiF solid-electrolyte interphase, which can effectively suppress Li dendrites and the chemical degradation of AN in contact with Li. Accordingly the electrolyte membranes exhibit a wide electrochemical stability window above 4.7 V versus Li+/Li and fire-retardant properties due to the presence of the phosphorus-containing polymer. Atomistic molecular modeling simulations have been performed to determine the structure of the electrolytes on the microscopic scale and to rationalize the trends in ionic conductivity and the transport regime as a function of the electrolyte composition. Finally, our electrolyte membranes enable stable cycling performance for LiFePO4|PMAPC1 + LiTFSI + AN|Li batteries.

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.

International audience; The effect of the post-annealing process on different properties of poly (L-lactic acid) (PLLA) nanofibers has been investigated in view of their use in energy-harvesting devices. Polymeric PLLA nanofibers were prepared by using electrospinning and then were thermally treated above their glass transition. A detailed comparison between as-spun (amorphous) and annealed (semi-crystalline) samples was performed in terms of the crystallinity, morphology and mechanical as well as piezoelectric properties using a multi-technique approach combining DSC, XRD, FTIR, and AFM measurements. A significant increase in the crystallinity of PLLA nanofibers has been observed after the post-annealing process, together with a major improvement of the mechanical and piezoelectric properties.

Fillers are widely used to improve the thermomechanical response of polymer matrices, yet often in an unpredictable manner because the relationships between the mechanical properties of the composite material and the primary (chemical) structure of its molecular components have remained elusive so far. Here, we report on a combined theoretical and experimental study of the structural and thermomechanical properties of carbon nanotube (CNT)–reinforced polybenzoxazine resins, as prepared from two monomers that only differ by the presence of two ethyl side groups. Remarkably, while addition of CNT is found to have no impact on the glass-transition temperature (Tg) of the ethyl-decorated resin, the corresponding ethyl-free composite features a surge by ∼47 °C (50 °C) in Tg, from molecular dynamics simulations (dynamic mechanical analysis measurements), as compared to the neat resin. Through a detailed theoretical analysis, we propose a microscopic picture for the differences in the thermomechanical properties...

Well‐defined pyrene‐based poly(2,2,6,6‐tetramethylpiperidinyloxy‐4‐yl methacrylate) (PTMA) (co)polymers have been synthesized and combined with multi‐wall carbon nanotubes (CNTs) as electrode material for organic radical batteries. The influence of the number of pyrene pendent groups on the electrochemical response of the nanocomposite materials has been assessed, focusing on the capacity retention upon charge/discharge cycling and on the cycling rate. In parallel, the interactions between the polymethacrylate chains and the CNT surface have been investigated with molecular modeling techniques, to shed light on the nature and stability of the functionalized PTMA/CNT interface.

We have shown in our first articles [1] [2] that even after encapsulation, the first rapid phase of degradation mechanism observed has been attributed to oxidation of interfaces and an alteration of the charges collection process. A second phase slower is induced by the oxidation of the active film, namely a decrease in the absorption and a degradation of the charge transport process. We revealed that another decrease in power conversion efficiency which has been induced by a possible interfacial passivation occurred at the organic/cathode interface, owing to the presence of residual oxygen, moisture and other impurities. This is in reality the real cause of the first rapid phase of degradation mechanism observed.

Water-soluble binders can enable greener and cost-effective Li-ion battery manufacturing by eliminating the standard fluorine-based formulations and associated organic solvents. The issue with water-based dispersions, however, remains the difficulty in stabilizing them, requiring additional processing complexity. Herein, we show that mechanochemical conversion of a regular poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) water-based dispersion produces a hydrogel that meets all the requirements as binder for lithium-ion battery electrode manufacture. We particularly highlight the suitable slurry rheology, improved adhesion, intrinsic electrical conductivity, large potential stability window and limited corrosion of metal current collectors and active electrode materials, compared to standard binder or regular PEDOT:PSS solution-based processing. When incorporating the active materials, conductive carbon and additives with PEDOT:PSS, the mechanochemical processing induces simultaneous binder gelation and fine mixing of the components. The formed slurries are stable, show no phase segregation when stored for months, and produce highly uniform thin (25 μm) to very thick (500 μm) films in a single coating step, with no material segregation even upon slow drying. In conjunction with PEDOT:PSS hydrogels, technologically relevant materials including silicon, tin, and graphite negative electrodes as well as LiCoO

WC/C:H thin films have been synthesized by a hybrid Plasma Enhanced Chemical Vapor Deposition/Physical Vapor Deposition method consisting in the reactive sputtering of a tungsten target in Ar-C2H2 atmospheres. The influence of the gas mixture on the physico-chemical properties of WC/C:H layers including their chemical composition, morphology, tribological and mechanical features has been studied. X-ray photoelectron spectroscopy measurements reveal an increase in the carbon content and a higher aliphatic bonds density in detriment to the carbide ones as a function of the acetylene flow. These results, in combination with Raman spectroscopy, X-ray diffraction, transmission electron microscopy and atomic force microscopy data, allow to depict the material as crystallized WxC1 − y nano-spheres (corresponding to aggregate of smaller nanograins of W2C and WC1 − x) diluted in a hydrogenated carbon matrix; the ratio between the hard crystallized WC phase and the softer hydrogenated carbon matrix being reduced when increasing the acetylene flow. The film nanohardness and tribological properties (i.e. friction coefficient and wear rate) are directly connected to the film chemical composition and structure. High nanohardness (~ 20 GPa), friction coefficient of μ = 0.5 and high wear rate (5.4 · 10− 13 m2/N) are obtained for the lowest carbon content of 37 at.%. When increasing the carbon content in the film (77 at.%), the hardness strongly decreases to ~ 10 GPa and a lower friction coefficient (μ = 0.2) and wear rate (4.7 · 10− 15 m2/N) are obtained. These properties are similar and even better than the ones of Cr(VI) based electroplating coatings, demonstrating the attractiveness of our WC/C:H films as a potential alternative to these coatings.

TiO2 nanotube arrays (TNA) elaborated on transparent and conducting substrates are promising materials for photoanodes in dye-sensitized solar cells as the reduced dimensionality enhances their transport properties. TNA were obtained by anodization of Ti films deposited by magnetron sputtering on transparent conducting oxide-coated glass. This study presents the impact of introducing a compact TiO2 underlayer on the morphological, optical and electrochemical properties of the TNA photoanodes.The TNA morphology was found to be more regular with a TiO2 underlayer and the macroscopic homogeneity of the samples was also increased. This is ascribed to a strong reduction, in the presence of the compact TiO2 underlayer, of a side reaction leading to oxygen evolution and destructuring the TNA film during anodization.As a consequence, the optical and transport properties (characterized by UV–vis and electrochemical impedance spectroscopy, respectively) were improved, together with an increased photovoltaic efficiency. Keywords: Dye solar cells, Nanotubes, Thin films, Sputtering, Anodization

We present a comparative molecular modeling study of the thermomechanical properties of crosslinked benzoxazine resins. A crosslinking algorithm was developed in order to simulate the thermal curing of thermoset resins and monitor the evolution of their network topology. The resin properties (gelation point, crosslink density, volumetric expansion, glass transition temperature, thermal expansion coefficient and elastic constants) were probed as a function of the network composition. The simulation results are in line with analytical models and in very good agreement with experimental data. Our molecular dynamics simulations provide a detailed rationale for the differences in the measured thermomechanical properties of recently reported benzoxazine derivatives and pave the way to the design of improved resins using predictive modeling tools based on the monomer chemical structure as the sole input.

This paper describes the synthesis and characterization of a new hybrid material based on poly(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl methacrylate) (PTMA) for lithium battery applications. Our strategy relies on the anchoring of nitroxide-embedding polymer chains onto multi-walled carbon nanotubes (MWCNTs). The resulting hybrid material (MWCNT-g-PTMA) not only prevents the solubilization of the PTMA active material but also benefits from its structural design aspects. The MWCNT-g-PTMA structure confers high performances thanks to the precise distribution of the PTMA redox material with respect to the MWCNT conductive network, as confirmed by molecular modeling simulations of the polymer/MWCNT interface. Physicochemical characterizations are evidence of the success of MWCNT-g-PTMA synthesis with a polymer loading up to 30 wt%. Electrochemical analysis shows the potential of MWCNT-g-PTMA as a battery material, with a capacity reaching 85% of the theoretical value, a good cyclability (retention > 80% after 150 cycles) and excellent power performances (capacity at 60C exceeding 65% of the nominal value).

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.

Patterned and layered hydrophilic/phobic coatings were deposited on multiple surfaces using nonfluorinated precursors (AA, acrylic acid; PMA, propargyl methacrylate) with an atmospheric pressure dielectric barrier discharge operating in open air. Water contact angles of the resulting films could be tuned from 135° (very hydrophobic) by adjusting the AA/PMA feed ratio and/or via postdeposition exposure of films to an Ar/O2 plasma treatment. Coatings could be applied to any surface and were seen to be water stable, due in large part to cross-linking induced from the reactivity of the PMA pendant groups. Hybrid hydrophilic/phobic patterns at submillimeter length scales, and philic/phobic/philic laminates were produced using a shadow mask and sequential deposition, respectively. Chemical heterogeneity of films was assessed using XPS, SIMS, and micro-IR imaging and suggest that localization of COOH and OH groups are primarily responsible for hydrophilicity. Overall, this work demonstrates that atmospheric pressure plasma polymerization is a simple and scalable method for robust and tunable control of wettability of surfaces of all kinds., SCOPUS: ar.j, info:eu-repo/semantics/published

A poly(3-hexylthiophene)-block-perfluoropolyether-block-poly(3-hexylthiophene) (P3HT-b-PFPE-b-P3HT) triblock copolymer was synthesized by copper(I)-catalyzed alkyne–azide cycloaddition (CuAAC) in 95% yield. The copolymer was unequivocally characterized by size exclusion chromatography reaching 27 000 g mol−1 and nuclear magnetic resonance (NMR). As expected, diffusion-ordered spectroscopy NMR experiment revealed a lower diffusion coefficient (2.56 × 10-10 m2 s−1) for the P3HT-b-PFPE-b-P3HT triblock copolymer than the ethynyl end-functionalized P3HT (2.83 × 10-10 m2 s−1). Such a triblock copolymer exhibits i) a good thermal stability with no significant weight loss until 320 °C under air, ii) a glass transition of -50 °C due to the soft PFPE segment and iii) a melting peak arising from P3HT at 236 °C. The UV–vis absorption spectrum exhibits a similar absorption profile to that of pure P3HT with a vibronic structure. Analysis of terpolymer thin films by atomic force microscopy imaging and grazing incidence wide-angle X-ray scattering reveals the formation of P3HT crystallites and an “edge-on” orientation of the polymer chains towards the substrate. Preliminary photovoltaic studies on blends of this triblock copolymer combined with a fullerene derivative indicate that the devices using P3HT-b-PFPE-b-P3HT show an almost similar power conversion efficiency to commercial P3HT.

End-functionalized poly(3-hexylthiophene) (P3HT) and poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) were synthesized using controlled polymerization techniques and linked together to lead to a diblock copolymer structure via click cycloaddition. These diblock copolymers were further blended with carbon nanotubes (CNTs) to be used as cathodes in organic radical batteries. The performances of these batteries were studied during charge/discharge cycling at constant and variable current densities (C rate). In order to shed light on the importance of the diblock copolymer architecture, the results were compared to the capacities measured on electrodes made of blends of P3HT and PTMA homopolymers. Theoretical simulations were finally used to corroborate the good electrochemical properties of the synthesized diblock copolymers.

The preparation and characterisation of a novel three‐dimensional organic material consisting of porphyrin arrays on carbon nanotubes embedded in an organogel is reported. Firstly, the porphyrin array was prepared through metal‐ligand coordination of a ditopic ligand (1,2‐bis(4‐pyridyl)ethane) and two bis‐Zn(II) porphyrins, linked through a pyrene core, and was studied through UV‐Vis, NMR and diffusion spectroscopies. Secondly, the porphyrin supramolecular architecture was adsorbed on pristine carbon nanotubes, greatly improving the dispersibility of the latter in organic solvents. The hybrid material was characterised by means of UV‐Vis spectroscopy, microscopic techniques and thermogravimetric analysis. Finally, by exploiting the anisotropic magnetic susceptibility of carbon nanotubes, the hybrid material was aligned under a magnetic field, the organisation of which could be maintained by in situ gelation. The resultant hybrid organogel exhibited notable optical anisotropy, suggesting an anisotropic arrangement of the porphyrin‐CNTs architectures in the macroscopic material.

Sepiolite (Sep)&ndash, styrene butadiene rubber (SBR) nanocomposites were prepared by using nano-sized sepiolite (NS-SepS9) fibers, obtained by applying a controlled surface acid treatment, also in the presence of a silane coupling agent (NS-SilSepS9). Sep/SBR nanocomposites were used as a model to study the influence of the modified sepiolite filler on the formation of immobilized rubber at the clay-rubber interface and the role of a self-assembled nanostructure in tuning the mechanical properties. A detailed investigation at the macro and nanoscale of such self-assembled structures was performed in terms of the organization and networking of Sep fibers in the rubber matrix, the nature of both the filler&ndash, filler and filler&ndash, rubber interactions, and the impact of these features on the reduced dissipative phenomena. An integrated multi-technique approach, based on dynamic measurements, nuclear magnetic resonance analysis, and morphological investigation, assessed that the macroscopic mechanical properties of clay nanocomposites can be remarkably enhanced by self-assembled filler structures, whose formation can be favored by manipulating the chemistry at the hybrid interfaces between the clay particles and the polymers.

© 2016 American Chemical Society. We report the synthesis of all-conjugated branched poly(thiophenes) with a control over the degree of nonlinearity via two different routes. In the first approach a branched monomer is polymerized using three different catalysts which differentiate in the degree of association to the π-system of the polymer backbone. In the second approach a copolymerization is performed with the branched and a linear monomer. In a next step the influence of the different degrees of nonlinearity on the optoelectronic properties is investigated by UV-vis and fluorescence spectroscopy. Finally, the thermal behavior, the morphology, and the electrical properties at the nanoscale of the material in solid state are studied using DSC and AFM techniques. ispartof: Macromolecules vol:49 issue:23 pages:8951-8959 status: published

This work deals with the synthesis and characterization of new diblock copolymers based on π-conjugated and depolymerizable units. These diblock copolymers are based on a regioregular poly(3-hexylthiophene) sequence associated with a sacrificial block, namely polyphthalaldehyde. The conjugated polymer was obtained by Grignard metathesis polymerization and end-capped by an alkynyl group while the depolymerizable segment was synthesized by an anionic cyclopolymerization from an azide moiety. Diblock copolymers with different molecular weights were then successfully synthesized via an alkyne–azide coupling reaction. Under specific conditions, these copolymers self-assemble into fibrillar nanostructures in thin films. The elimination of polyphthalaldehyde was carried out by thermal treatment, generating nanoporous poly(3-hexylthiophene) films. The use of a dry treatment to remove the polyphthalaldehyde block strongly reduces the morphological damages that would occur with a “wet” processing route. These nanop...

Hybrid solar cells are in sustained development among the photovoltaic (PV) technologies. Molybdenum diselenide (MoSe 2 ) is a promising alternative semiconductor for hybrid PV due to its absorption in the near-infrared spectrum, its good carrier transport and its ability to form 2D structures. Scanning Spreading Resistance Microscopy (SSRM) is used for the electrical characterization of crystalline Nb-doped MoSe 2 . An n-type nature of doping is demonstrated, with local accumulation of dopants in the crystal when substituting Mo atoms by Nb in a 0.01% stoichiometric ratio. On the basis of the SSRM measurements, a band structure for the probe-sample system is proposed. Blends are also prepared with the p-type semiconducting polymer poly(3-hexylthiophene) (P3HT) and the photo-electrical properties of those Nb-doped MoSe 2 :P3HT systems are studied at the nanoscale by PhotoConductive-Atomic Force Microscopy (PC-AFM).

PDMS-b-PAA block copolymers were synthesized in a two-step procedure. The first step involves atom transfer radical polymerization (ATRP) of the protected ethoxyethyl acrylate (EEA) monomer initiated with α-bromopoly(dimethylsiloxane) (PDMS) ( $$ \bar{M}_{\text{n}} $$ = 10,000 g/mol) macroinitiator. In the second step the synthesized poly(dimethylsiloxane)-b-poly(ethoxyethyl acrylate) (PDMS-b-PEEA) was deprotected by thermal treatment. The aggregation properties of the copolymers were investigated by atomic force microscopy (AFM) and dynamic light scattering (DLS). The influence of the polymer concentration, the length of the PAA block, the (mixed) solvent composition, and annealing on the size and the shape of the aggregates was evaluated. The results show that the aggregate size and morphology can be successfully controlled by tuning the experimental conditions. These copolymers might possibly be used in the preparation of adhesive materials.

© 2015 American Chemical Society. Conjugated graft copolymers consisting of a chiral poly(phenyleneethynylene) (PPE) backbone and poly(3-hexylthiophene) side chains (P3HT) with different grafting degrees were synthesized. While PPE was prepared by classical Sonogashira couplings, the end-functionalized P3HT was prepared by a controlled Kumada catalyst transfer polycondensation (KCTP) allowing the installation of an acetylene end group. After some postpolymerization reactions on the PPE to introduce azide groups, the P3HT was clicked to the PPE through the CuAAC coupling reaction. Subsequently, the (chiral) self-assembly of these materials was studied by means of UV-vis and CD spectroscopy, AFM, and DSC. Finally, fluorescence spectroscopy is used to study the quenching of the PPE fluorescence by P3HT. ispartof: Macromolecules vol:48 issue:24 pages:8789-8796 status: published

Chlorophyll a derivatives were integrated in &ldquo, all solid-state&rdquo, dye sensitized solar cells (DSSCs) with a mesoporous TiO2 electrode and 2&prime, 2&prime, 7,7&prime, tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9&prime, spirobifluorene as the hole-transport material. Despite modest power conversion efficiencies (PCEs) between 0.26% and 0.55% achieved for these chlorin dyes, a systematic investigation was carried out in order to elucidate their main limitations. To provide a comprehensive understanding of the parameters (structure, nature of the anchoring group, adsorption &hellip, ) and their relationship with the PCEs, density functional theory (DFT) calculations, optical and photovoltaic studies and electron paramagnetic resonance analysis exploiting the 4-carboxy-TEMPO spin probe were combined. The recombination kinetics, the frontier molecular orbitals of these DSSCs and the adsorption efficiency onto the TiO2 surface were found to be the key parameters that govern their photovoltaic response.

International audience; Poly(3-hexylthiophene)s end-functionalized with p-extended porphyrins have been synthesized in a one-pot procedure. The polymers show a broad absorption profile extending to 700 nm and a fibrillar microstructure, which can be tuned through judicious selection of the porphyrin molar ratio.

To succeed in commercial applications, donor materials for organic solar cells should combine high stability and simple synthesis with high performance in devices. Here, we present a new small pi-conjugated molecule, TPA-T-DCV-Ph, which meets those requirements. Simple and efficient three-step synthesis produces a push-pull molecule with triphenylamine donor and phenyldicyanovinyl acceptor groups, which is suitable for both solution processing and vacuum deposition. The unique property of TPA-T-DCV-Ph is an unusually long exciton diffusion length of > 25 nm due to the combined effect of long exciton lifetime and surprisingly low energy disorder. This, together with a device engineering, resulted in > 5% efficiency for TPA-T-DCV-Ph:C-70 vacuum-processed solar cells. The results obtained are envisioned to be further improved by optimizing the absorption of the molecule and light management in the device which can push the efficiency even further.

The nanoscale morphology of photoactive hybrid heterojunctions plays a key role in the performances of hybrid solar cells. In this work, the heterojunctions consist of a nanocolumnar TiO2 surface covalently grafted with a monolayer of poly(3-hexylthiophene) (P3HT) functionalized with carboxylic groups (–COOH). Through a joint analysis of the photovoltaic properties at the nanoscale by photoconductive-AFM (PC-AFM) and surface photovoltage imaging, we investigated the physical mechanisms taking place locally during the photovoltaic process and the correlation to the nanoscale morphology. A down-shift of the vacuum level of the TiO2 surface upon grafting was measured by Kelvin probe force microscopy (KPFM), evidencing the formation of a dipole at the TiO2/P3HT-COOH interface. Upon in situ illumination, a positive photovoltage was observed as a result of the accumulation of photogenerated holes in the P3HT layer. A positive photocurrent was recorded in PC-AFM measurements, whose spatial mapping was interpreted consistently with the corresponding KPFM analysis, offering a correlated analysis of interest from both a theoretical and material design perspective.

International audience; Conjugated poly(3-hexylthiophene) copolymer derivatives containing 10% appended porphyrin moieties are prepared using a supramolecular approach toward applications in organic electronics. The self-assembled polythiophene–porphyrin copolymers are synthesized by coordinationof the porphyrinato central zinc ions to the imidazole-functionalized polythiophene side chains.Evidence for the self-assembly process is provided by 1H NMR spectroscopy, single crystal X-ray diffraction, and optical absorption studies on model compounds. The polythiophene–porphyrin copolymers show an extended absorption window in the region of 420–650 nm due to the contribution of the porphyrin. Photoluminescence studies indicate concentration dependent energy transfer from P3HT to the porphyrin. Preliminary photovoltaic studies are performed by combining the polythiophene–porphyrin copolymers with PC 61 BM in the photoactive layer of bulk heterojunction organic solar cells.

The atmospheric pressure PECVD deposition and texturization of hydrophobic coatings using liquid fluorinated C6F12 and C6F14 precursors are investigated. The effect of the carrier gas (argon and helium) is discussed in terms of the behavior of the gas phase and of the characteristics of the deposited film. Mass spectrometry measurements indicate that the fragmentation is higher with argon while helium reacts very easily with oxygen impurities leading to the formation of CxFyOz compounds. These observations are consistent with the chemical composition of the films determined by XPS and the variation in the deposition rate. Moreover, the streamers present in the argon discharge affect the morphology of the surface by increasing the roughness, which leads to the increase in the hydrophobicity of the coatings.

In this work, glancing angle deposition and magnetron sputtering are combined to synthesize nanostructured Ti films. Different type of microstructures (tilted columns, straight pillars, zigzags) are obtained as a function of the experimental conditions. As a support, kinetic Monte Carlo simulations are performed to understand the observed trends using the NASCAM (NAnoSCAle Modeling) code. The latter is used to simulate the growth of the films and to explain the effect on the obtained structures of experimental parameters such as the substrate temperature, the gas pressure as well as the substrate tilting and rotation speed. NASCAM enables quantitative prediction of the density, the surface roughness, and the column shape asymmetry. In addition, the effective porosity (ϕ e ) of the structures was evaluated from the simulation data for two molecules presenting different size (0.64 and 3.20 nm). The results show that ϕ e decreases with the size of the adsorbed molecule, from above 50% for the small molecule to below 10% for the larger one. This is understood by considering the accessibility of the pore as a function of the size of the molecules. These data are correlated to experimental results obtained by transmission electron microscopy.

The association of kinetic studies, DFT calculations and 1H–7Li NMR analyses allowed the control of the cyclo-ATRP of PEG9DMA and the production of polymethacrylate pseudo crown-ethers of various molar masses. Their potential to act as a solid-state polymer electrolyte in Li-ion batteries has been highlighted and may come from the supramolecular organization of the cyclo-PEG forming a Li+ diffusion channel.

In the rapidly developing field of organic photovoltaics, the material design and device engineering are key factors that eventually determine the device efficiency. Design of the active layer material and intermolecular interactions largely determine the efficiency of organic solar cells. In this study, the authors discuss ultrafast photophysics of four star-shaped molecules (SSMs) as benchmark materials with time-resolved photoinduced absorption and photoluminescence spectroscopy as experimental tools. The authors show that efficient exciton-to-charge conversion occurs in SSM films even without an external acceptor. This results in the lowering of the Coulomb binding between intermolecular electron- hole polaron pairs which, in turn, can lead to an increased open-circuit voltage. The findings suggest that promoting intermolecular interactions in films of small organic molecules is one of the pathways to highly efficient organic solar cells.

This chapter discusses the applicability of different AFM -based techniques with force sensitivity of a few pN for mapping the nanostructure and quantifying the nanoscale mechanical properties of the surface of complex polymer coatings based on silicone oligomers in order to use them as bioadhesives . The AFM modes used are Peak Force Tapping and Contact with Si3N4 and chemically-modified (CH3-terminated alkanethiols, COOH-terminated alkanethiols) probe tips both in air and aqueous media. Studying nanostructured films of block copolymers containing a polydimethylsiloxane (PDMS) segment and a segment of poly(acrylic acid) (PAA ) or poly[(2-dimethylamino) ethyl methacrylate] (PDMAEMA ) led to a better understanding of the interaction of the polymer chains with solvent molecules or chains of another polymer in the self-assembly process. Stiffness mapping by PFT-AFM has allowed identifying the difference in mechanical properties between two polymer constituting blocks. The effect of copolymer concentration and solvents on the surface morphologies was also studied in details. In more complicated situation, the copolymers were used to modify the surface properties of elastomeric PDMS coatings and the PDMS surface properties before and after immersion in water were also evaluated. AFM -based nano-mechanical testing showed that the surface reorganization significantly affects the morphology and the adhesion properties of the silicone coatings. The observed broadening of the adhesion distribution is believed due to the different interactions between hydrophobic /hydrophilic surfaces and the silicon probe tip in aqueous solution. Finally, the nature of the tip-surface interaction forces was clarified by employing functionalized AFM tips. The adhesion force mapping with hydrophobic tips (CH3-terminated alkanethiols) for 10 wt% PDMS-b-PDMAEMA-filled coatings before and after immersion in water showed larger forces for the coatings before immersion, thus confirming that the interaction forces between two hydrophobic surfaces are stronger than those between one hydrophobic and one hydrophilic surface. In addition, the interaction forces between amino groups of the PDMAEMA and COOH-terminated tips were investigated as a function of the pH and the ionic strength of aqueous media. Progressive stretching and continuous desorption of individual copolymer chains from the tip surface were recorded. The dynamic changes of polymer desorption were also reported by recording force curves at various pulling speeds and contact times. Furthermore, the adhesion force maps recorded at high ionic strength (in 0.1 M NaCl solution) showed a major decrease in the adhesion frequency and plateau forces, indicating a loss of polyelectrolyte properties. Bio-adhesion experiments with mussels were then performed on the different types of substrates—unfilled PDMS coatings and PDMS coatings filled with block copolymers. The results revealed that these organisms attach preferably to block copolymer-filled coatings after immersion due concomitant molecular reorganization at the top-surface of the copolymer-filled coatings. These observations provided evidence for the significant role played by the selected amphiphilic block copolymers to promote bio-adhesion on surface-treated silicone coatings.

The performance of organic nanostructures is closely related to the organization of the functional molecules. Frequently, molecular chirality plays a central role in the way molecules assemble at the supramolecular level. Herein we report the hierarchical self-assembly of benzo-fused tetrathia[7]helicenes on solid surfaces, from a single surface-bound molecule to well-defined microstructures, using a combination of various characterization techniques assisted by molecular modeling simulations. Similarities as well as discrepancies are revealed between homochiral and heterochiral aggregations by monitoring the hierarchical nucleation of helicenes on surfaces, where the impact of enantiopurity, concentration and adsorbate-substrate interaction on molecular organization are disclosed. ispartof: Nanoscale vol:9 issue:45 pages:18075-18080 ispartof: location:England status: published

Polymers are lightweight, flexible, solution-processable materials that are promising for low-cost printed electronics as well as for mass-produced and large-area applications. Previous studies demonstrated that they can possess insulating, semiconducting or metallic properties; here we report that polymers can also be semi-metallic. Semi-metals, exemplified by bismuth, graphite and telluride alloys, have no energy bandgap and a very low density of states at the Fermi level. Furthermore, they typically have a higher Seebeck coefficient and lower thermal conductivities compared with metals, thus being suitable for thermoelectric applications.We measure the thermoelectric properties of various poly(3,4-ethylenedioxythiophene) samples, and observe a marked increase in the Seebeck coefficient when the electrical conductivity is enhanced through molecular organization. This initiates the transition from a Fermi glass to a semi-metal. The high Seebeck value, the metallic conductivity at room temperature and the absence of unpaired electron spins makes polymer semi-metals attractive for thermoelectrics and spintronics. Refereed/Peer-reviewed

The molecular arrangements of two different alkylsubstituted oligothiophenes, α,α′-dihexylquaterthiophene (DH4T) and α,α′-dioctylterthiophene (DOTT), in monolayers on molybdenum disulfide (MoS2) were studied with a joint theoretical/experimental approach. Scanning tunneling microscopy was used both at the liquid/solid interface and in dry conditions to investigate the ordering of the conjugated oligomers in two-dimensional layers. DH4T and DOTT form well-ordered monolayers at large scales with interdigitated packing on MoS2. In addition, DOTT exhibits an arrangement in which a dimer-type stacking of the conjugated backbone with an interlocking of the alkyl side chains is formed. Molecular modeling simulations have been used to provide insights into the microscopic morphology and to assess the stability of the different assemblies of DOTT and DH4T on MoS2.

We report on the synthesis of new thermally cross-linkable all-conjugated diblock copolymers composed of a poly(3-hexylthiophene) (P3HT) block and an acrylate-functionalized polythiophene block. These copolymers are then used in bulk heterojunction (BHJ) solar cells with [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and their photovoltaic performances are compared with standard P3HT/PCBM devices. Thermal cross-linking of the functional copolymers/PCBM blends is performed to improve the thermal stability of the active layer. BHJ photovoltaic cells with cross-linkable copolymers and PCBM show initial power conversion efficiencies slightly lower than that of P3HT devices. However, solar cells with cross-linkable copolymers retain more than 85% of their initial power efficiency value after 165 h of thermal annealing (accelerated aging test), whereas the same devices with P3HT retain less than 65% of their initial power efficiency. This improvement of the thermal stability of BHJ photovoltaic cells is the...

An easy and quantitative cyclization procedure based on an intramolecular imperfect aldol reaction from a pre-generated regioregular poly(3-hexylthiophene) is developed. As an illustration of the versatility of this procedure, the synthesis of a representative macrocyclic poly(3-hexylthiophene) with a diameter of 5 nm is presented.

The waterborne nature of radiation curable polyurethane dispersions largely respond to the current environmental concerns and do not require any additional coalescent since the film formation (drying) and hardening (photo-curing) take place in distinct steps. It is possible to design aqueous dispersions with distinct polymer particle populations resulting in micro-structured coatings with optimized properties over a wide range of curing conditions. Mixed dispersions based on hard and soft acrylated polyurethane particles were used as model systems for the present study. The minimum film formation temperature has been investigated as a function of the hard:soft polymer ratio. The elastic modulus of the dry coatings shows a reinforcing effect consistent with the inclusion of hard domains in a soft continuous matrix. However, the level of reinforcement is not properly predicted by the usual mechanical models and it is qualitatively accounted for by assuming a composition gradient (interphase) between the hard domains and the matrix. The multiple-phase structure was clearly established by Atomic Force Microscopy in agreement with thermal analysis data. Furthermore the local nanoscale mechanical properties were mapped using a new imaging mode based on real-time force–distance curve analysis. Finally, the coatings prepared using this multiple-phase pattern present a clear benefit over conventional homogeneous coatings by offering an improved balance of chemical and mechanical resistance in pigmented systems applied on melamine-coated MDF panels.