Research project P7/05 (Research action P7)
The IAP Functional Supramolecular Systems will identify and demonstrate new fundamental concepts in light conversion and manipulation, in catalysis and separations, and in design of responsive and adaptable systems, based on concepts of supramolecular assembly and function.
The vertical project structure (WPs) reflects the main functions that we aim at:
WP 1. Adaptable, responsive systems
Here we design supramolecular assemblies that reconfigure as a response to stimuli, such as heat, pH, light, electrode or redox potential, mechanical stress, electric or magnetic fields, CO2 pressure, concentration of analytes (sugars, nucleotides, ..), etc. The challenge is to use multiple or localizable stimuli and responses, and to realize a major leap in the operational window of the materials. The applied stimuli will be controlled temporally and spatially, down to the 10 nm scale; responses and optical or electrochemical signals are recorded in the same spatiotemporal range. The systems can be 2D structures such as (nanopatterned) ultrathin films and monolayers, 3D structures such as porous materials and gels, or microfluidic channels that open or close under external stimuli. The systems are typically based on functional macromolecules, semiconducting or conducting polymers, ferroelectric polymers, synthetic and natural polyelectrolytes including biomacromolecules (polysaccharides, proteins, DNA, RNA), colloids or nanoparticles.
Depending on the design of the supramolecular assembly, the systems can be used for actuation and controlled motion of nanoparticles, for storage and delivery (of drug molecules, gases), for controlling adhesion, for switching, as microfluidic sensors or sensor arrays, as adaptive smart nanoparticles, as self-healing (polymeric) materials for coatings and thermosets. We will also study their capability to exert control on biological systems, e.g. regarding proliferation or adhesion.
WP 2. Supramolecular catalysis, photocatalysis and advanced separations
Within the catalysis work, attention is focused on multifunctional catalysts, on photocatalysis, and on responsive catalysts that change their activity as a response to a stimulus. New separation concepts are primarily based on molecular recognition in 3 or 3D structured systems. A grand challenge is to convert new feedstocks (CO2, renewables) using catalysts that are designed for durability.
Multifunctional catalysts are designed based on a modular approach, in which inorganic or organic building blocks are assembled to form pores, cages in 2 or 3 dimensions, with precise electronic control over the active site(s). Exemplary materials are new templated zeolite materials, self-assembling porous coordination polymers, carbon-inorganic hybrids, or polymeric support particles. Photocatalysts are designed via a bottom-up approach, by assembling organic antennae molecules around inorganic, doped nanoclusters. The matrix around the photoactive centre is designed to adsorb volatile contaminants or reactants and to collect impinging light, e.g. via concepts of plasmonics and by integration in photonic crystals. Identification of intermediates and their properties will be achieved via fast spectroscopy; the heterogeneity of structure and function will be studied via (non)-optical microscopy. Multiphase catalysis involving supercritical (sc) CO2 will be addressed, e.g. with development of tensioactive agents for the water/scCO2 interface.
Supramolecular materials for separations will be designed on 2D surfaces, in 3D porous materials and in structured membranes.
WP 3. Supramolecular systems for energy conversion
In the area of photovoltaics, the aim is to develop architectures that go beyond current bulk heterojunction-based photovoltaic devices. The global challenge is to reach joint control of the microscopic morphology, the optical properties and the electrical response in ternary organic solar cells. This can only be achieved by fine control of the supramolecular interactions and supramolecular ordering, combined with novel approaches to materials processing. Focus will be put on improved light absorption and energy transfer, by design of low bandgap, highly ordered molecular and (co)polymer materials. Charge transport and collection will be promoted via supramolecular assembly in multifunctional materials, i.e., systems designed to simultaneously (i) favor interaction with oxide nanostructures or metal nanoparticles, (ii) improve charge transport in the semiconducting layers, (iii) control the morphology of the p-n junctions.
In this context we will also explore the reversible conversion of light to plasmons on tailored metallic nanoparticles (plasmonics). Optimized and new supramolecular design concepts (e.g. templating with mesoporous materials) will be developed to arrange metal NPs into plasmonic antenna structures. The use of such plasmonic antennas to improve light absorption and transport to the site of charge dissociation in photovoltaics (as well as in catalysis) will be explored.
Finally, in the domain of OLEDs, hybrid, supramolecularly organized systems will be taken to the device level.
The horizontal project structure (platforms) gathers and develops new expertise for studying the supramolecular systems. Strong links are also expected between the platforms, e.g. in theory-based design of materials, or prediction of spectral properties of new materials.
Platform 1. Synthesis and fabrication
We will prepare building blocks for supramolecular systems, such as small conjugated molecules, multinuclear transition metal complexes, conjugated polymers, tensioactive polymers, (gradient) block copolymers, polymers with discrete molecular weights, inorganic nanoparticles, etc, using green media wherever possible. New challenging methodologies will be developed, e.g. novel combinations of controlled/living polymerization techniques, additive-free click chemistry, site-specific functionalization, or exploitation of non-equilibrium self-organization. Fabrication methodologies include (templated) self-assembly in 2D or 3D, layer-by-layer assembly, guided adsorption, micro-, nano- and soft lithography combined with self-assembly, atomic layer deposition, wetting and dewetting, confined crystallization, mini-emulsion polymerization, model-guided design, supercritical processing, reactive processing of nanoparticles. Organic photovoltaic materials will be integrated in devices to allow testing. The supramolecular assemblies are shaped as nanoparticles, films, membranes, microspheres, capsules, foams, composites etc, with well-controlled hierarchy.
Platform 2. Advanced characterization
The aim here is to study structure, function and dynamics of the self-assembling systems down to the single molecule level or below, with the best temporal, spatial and spectral resolution. This requires access to state-of-the-art characterization tools and development of new and dedicated imaging facilities. Therefore this platform gathers cutting edge expertise in electron microscopy (with special attention devoted to soft matter such as polymeric or hybrid materials), in ultraresolution (non-)linear optical microscopy (PALM, STORM, CARS, SHG) and in scanning probe techniques (STM, AFM). Other central tools are QCM-d, XPS, XRR, time-resolved X-ray absorption (XAS) techniques, (GI-)WAXS, NMR, ultrafast spectroscopy etc. As grand challenges we aim to develop and optimize electron microscopy techniques dedicated to quantitative 2D and 3D imaging of soft matter, at the nanometer and sub-nanometer level (e.g. to address buried interfaces) and to explore the integration of techniques, such as the combination of electron microscopy with optical microscopy.
Platform 3. Multiscale modeling and model-guided design
A multiscale modeling approach is required to study the structure, the function, the spectroscopic signatures, the transport processes (e.g., electron or atom transfer) and the dynamic behavior of the supramolecular systems. This approach covers the range of complexity starting from simple structures (single molecules and molecular building blocks) up to supramolecular, self-assembled and macromolecular systems and includes the description of processes occurring at organic/organic and organic/inorganic interfaces. For these purposes, the development of advanced, complementary tools is required, starting from state-of-the-art quantum chemical methods (0.1-10 nm) to force-field simulations (10-100 nm) to mesoscale modeling (100 nm-1μm). The grand challenge here will be to establish an integrated modeling platform based on multiscale modeling techniques, which will be dissipated within the network to study and design multifunctional supramolecular systems, catalysts and devices. The dynamics in space and time will be studied starting from chemical kinetics at molecular level to microkinetics, based on the mean-field approximation, which allows to account for the complexity of the molecular level combined with the transport phenomena at larger time and length scales. Advanced chemoinformatics and chemometrics will allow efficient data storage, data mining, molecular pattern recognition and functional screening and provide quantitative structure-function relations.
