The European Academy of Sciences has awarded the 2020 Leonardo da Vinci Award to Prof. Klaus Müllen for his outstanding activity in the field of physical organic chemistry.
Klaus Müllen received his academic training in physical and physical organic chemistry, later held a chair in organic chemistry and became director at the Max Planck Institute for Polymer Research where he was responsible for macromolecular synthesis. Deeply rooted in methods of organic synthesis and with an emphasis on organic electronic materials, he introduced a wealth of new polymer architectures, but also advanced the need for precision polymer synthesis. Many of his polymers have become classics of materials science.
His work stands out for both depth and breadth, extending from organic colorants to conjugated polymers, from graphenes to polyolefins and from organic-inorganic composites to functional organic nanoparticles. His whole scientific career is a tribute to interdisciplinarity and trustworthy collaboration. This has allowed their consortia to jointly make major contributions to nanoscience, photophysics, device fabrication, sensing and even tumor therapies. In his belief, materials synthesis must, first, be reliable to allow sound structure-property relations and to rationally „synthesize desired properties and functions“, and, secondly, include methods of processing, i.e. of creating defined macroscopic states of matter. Along these lines, he has described liquid-crystalline phases, thin films and fibers with unique supramolecular architectures.
In 1995 his group published a seminal paper on large polycyclic aromatic hydrocarbons together with their electronic characterization by scanning tunneling microscopy. By making these disc structures larger and larger, they have established the class of „nanographenes“ . These, in turn, have culminated in the synthesis of graphene nanoribbons, a new type of electronic materials bridging the worlds of conjugated polymers and graphenes. Classical polymer synthesis is thereby combined with synthesis after immobilization of monomers on surfaces and even with chemical vapor deposition.
In Klaus Müllen’s research, creativity in synthesis has always served a goal in materials research. In 2007, they published a first paper towards nowadays widely used donor-acceptor polymers as semiconductors for organic field-effect transistors . Likewise, their graphene nanoribbons are not only relevant for established device applications, but also for spintronics and even for future quantum computing. From a strategic point of view, their graphenic (2D-) structures are made from multiply branched (3D-) polyphenylene precursors. The latter, in turn, are functional materials in their own right as shape-persistent, tree-like polymers (dendrimers) for biomedicine, light harvesting and catalysis.