This project aims at the convergent synthesis of carbon nanobelts, i.e. carbon nanotubes shorter than wide, and related highly condensed lath-shaped polycyclic aromatics, i.e. short graphene ribbons. Both classes of materials are of interest for organic electronics and optoelectronics as well as model compounds for extended nanotubes and graphene ribbons. The laths also serve as guinea pigs for the optimization of reactions ultimately leading to the targeted carbon nanobelts, which may serve as seeds for the controlled growth of nanotubes of homogeneous chirality and width, and thus homogeneous electronic properties. The targeted nanobelts include armchair, zigzag and chiral belts, and range in diameter from values equal to the diameter of C60 to approximately twice that value (7 to 12Å), spanning thus essentially the mainstream diameter range of single wall carbon nanotubes. The synthetic approach to these belts is based on a limited set of condensation reactions that first couple bifunctional bricks to flexible conjugated macrocycles that are themselves of interest as cyclic analogs to conjugated polymers, and then rigidify these flexible rings in a second step to fully condensed, fully aromatic belts. Macrocycle formation under high dilution conditions is eased by a molecular design that relies on the configurational zig-zag-like flexibility of multiple cis-vinylene links between the arylene fragments, and the build-up of sterical strain is essentially relegated to the next intramolecular condensation step performed on the already-built macrocycle. The starting bricks, oligomeric intermediates and final rigidified products are designed to bear multiple flexible substituents to ensure good solubility and thus reactivity and characterizability all the way through the synthetic build-up. The substituents are chosen so that they may be taken off subsequently to offer access to the unsubstituted lath- and belt-shaped, fully conjugated, condensed hydrocarbons in a last step. This project is in full agreement with the scientific program presented four years ago by the project leader upon his recruitment application at the CNRS, and is the result of preliminary studies performed during the past two years in order to elaborate an optimized synthetic approach to carbon nanobelts and related ribbon-type analogs.

Bioinspired microdevices are the prelude to a great advance in biomedical technologies. However, there is a clear gap in fabricating prototypes of the size and complexity of cells. Active colloids are an experimental paradigm to realize microrobots due to their ability to self-propel and perform simple tasks, although they fail to provide autonomous units due to their limited geometries and materials, and lack of autonomy. Conversely, artificial cells capture self-regulated processes reminiscent of their biological counterparts but lack cell-mimetic motion. The creation of autonomous cell-mimetic units combining motion and functionality offers exciting opportunities for the creation of bioinspired microrobots. However, identifying the minimal designs and core elements remains an open challenge. The aim of MIMESYS is to deliver a unique cell-mimetic assembly combining synthetic and biological materials into a motile and autonomous microdevice. This will be achieved by encapsulating enzyme-functionalized active colloids inside giant lipid vesicles (GUVs) into a minimal cell-mimetic architecture. This project provides an experimental model with chemical signals as a behavioural-regulation pathway. The enzymatic particles serve as receiver/sender of chemical signals regulating motion, group dynamics, and functionality; while the GUV acts as an adaptive and permeable container. These units will efficiently navigate complex scenarios, communicate, and perform simple tasks autonomously. MIMESYS will confront the current limitations, leading to a better understanding of the fundamental precursors and conditions to engineer minimal models of motile artificial cells, opening up a new area on biomimicking microdevices. The fundamental outcome of this ANR JCJC project will set the benchmark for future and more complex approaches, addressing gaps in the fields of synthetic biology and active matter.

In a context where new technologies require ever-increasing functional materials, the field of bottom-up design has recently seen the emergence of strategies to greatly extend the range of crystalline phases accessible to colloidal self-assembly, securing a viable path to novel materials with exciting properties. In this context, we will forge a self-assembly pathway to colloidal chiral gyroids and clathrates, motivated by their valuable properties in photonics and mechanics. This project aims at (i) the definition of the self-assembly strategies to the colloidal structures of interest with the help of computer simulations, (ii) the synthesis of the suitable building blocks in bulk, (iii) the experimental in-situ study of their DNA-guided assembly by a combination of advanced techniques.

The use of bionanoparticles and more specifically of viruses, as building blocks for generating highly organized materials with hierarchical structures, is an emerging field in material science and biotechnology, because of unique features and advantages exhibited by viral particles: high degree of symmetry, uniformity in size and shape, well-characterized surface chemistry, ease of production, robustness, biocompatibility... Viruses appear therefore as versatile and functional organic protein-based supramolecules for chemists and as model structural entities for soft condensed matter physicists. In this project, we propose to focus on a filament-shaped virus, the bacteriophage fd. The raw fd virus has been already successfully studied as model system of rod-like particle self-organizing into liquid crystalline states. Our challenge is to produce new virus-based colloids with thermoresponsive properties and to study their phase behavior in suspension at the single particle scale, thanks to their colloidal size. The specificity of reactive chemical functions on fd virus surface are a major asset to regio-functionalize this virus and to develop new colloidal particles, paving the way for the elaboration of complex self-assemblies. Our goal is to monitor the self-organization of our virus-based functionalized colloids not only by the particle concentration, but also reversibly by temperature thanks to the specific chemical grafting on virus of thermoresponsive (co)polymers. Two new virus-based systems will be developed in our project: 1) The formation of colloidal amphiphiles by covalently bonding two viruses by their endpoints, the first pristine virus being hydrophilic and the second hydrophobic at high temperature due to the grafting of a thermoresponsive polymer (such as poly(N-isopropylacrylamide), PNIPAM) on its surface. The dual (hydrophilic virus)-(hydrophobic virus) system will then form rod-like patchy colloids, having temperature as tunable parameter for directing the self-assembly. Such patchy particles represent the first colloidal system mimicking molecular amphiphiles, for which superstructures from a few particle units (“colloidal molecules”) to real three-dimensional self-assemblies will be obtained. Thanks to the colloidal size and time, investigations of the self-assembly and phase transitions mechanisms involved in amphiphilic systems will be studied. 2) The induction by temperature of hydrophilic rods with tunable effective diameter thanks to the chemical modification of the whole viral surface by diblock copolymers. The first inner block grafted to the virus surface will be thermoresponsive (e.g. PNIPAM), whereas the second outer block exposed to the solvent will be hydrophilic whatever the temperature. The effective diameter associated with the chemically modified virus will be then tunable with temperature, maintaining meanwhile the colloidal stability of the dispersion (avoiding gel states). According to Onsager theory of the isotropic liquid to nematic phase transition, this change of particle diameter, keeping hydrophilic the biocolloids, will induce phase transition into liquid crystalline states. This strategy of functionalization by tuning the effective particle diameter with temperature will be then extended from our model system of viral rod-like particles to dispersions of technological interest: the carbon nanotubes (CNTs). Taking advantage of the colloidal scale of the rod-like fd viruses allowing for their visualization and the tracking of single particle with optical microscopy, structural and dynamical studies of self-organization and phase behavior of both virus-based systems will be performed as a function of temperature thanks to the functionalization with thermoresponsive (co)polymers. This approach should therefore open new pathways in the control of anisotropic (nano)particles into hierarchical structures organized at the mesoscopic or macroscopic length scale.

The miniaturization of electronic components is a major challenge. In computer sciences, it is expected by 2019 that Moore’s law will not be able to be respected with classical “top-down” strategies for miniaturization (photolithography…). New approaches and new techniques need to be developed. For data storage and information processing, a potential solution to this large problem can come in the form of single-molecule magnets (SMMs) or single chain magnets (SCMs) as these materials show appealing and potentially useful properties at the molecular scale. Their ability to store information at a nanometric scale makes them ideal candidates for future information storage devices as they offer a potentially much higher information storage density. In addition, their quantum properties can also be used as “qubit” for future quantum computers. This research project aims at the synthesis, the study and the functionalization of new redox-active SMMs or SCMs with enhanced properties, through a rational design of the molecular components. The redox activity will be provided either by the metal centre or the bridging ligand, or both. This will allow us to tune and sometimes to enhance significantly the magnetic properties of the resulting molecular architectures, with the goal of making molecular magnets with higher operating temperatures, which is a long standing challenge in this research area and a requirement for industrial applications. The first step for this project will be to make a new class of ligand specially designed i) to act as a redox-active bridge between the metallic spin carriers with the possibility of being stabilized in a radical form, ii) to promote the formation of metal carbon bonds, iii) to stabilize delocalized mixed valence states to promote interesting electronic, optical and improved magnetic properties. For the metallic spin carrier, the primary focus will be on using 4d/5d metal for several reasons, explained in this proposal, which make them ideal candidates to promote higher operating temperature for the SMMs and SCMs they will be part of. Initially bimetallic “prototype” systems will be synthesised by reaction of the bridging ligand with “capped” metal centres. This will allow us to undertake complete magnetic and electronic studies of both the metal centres and ligand within the complex. The isolation of these prototype systems will allow the selection of the most interesting building blocks for the synthesis of polynuclear complexes as potential SMMs as well as one dimensional coordination networks with potential SCM properties, with a better understanding of their behaviour. All these new potential enhanced SMMs/SCMs will be fully characterized and investigated. As well as creating a number of new potential SMMs/SCMs, the bridging ligand will be functionalized by different suitable groups in order to i) “tune” its redox/electronic properties, ii) to increase the solubility, iii) isolate magnetically the complexes or chains, iv) add liquid crystalline properties to the molecular assemblies toward organized magnetically active films. All the new isolated complexes or chains will be fully characterized by a large number of techniques including X-ray diffraction, cyclic voltammetry, UV/Vis/NIR and IR spectrometry, NMR, calorimetry, SQUID magnetometry and EPR. This will give us a comprehensive understanding of all the properties of the new complexes. The achievement of this innovative and ambitious research proposal should have a strong impact in the molecular magnetism community, and could contribute to the next generation of some basic components of computers.