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N°29 I quarterly I APRIL 2013 Profile | 19 BY Laure CAi lloce Gero Decher’s research features in the Top 10 of the most cited publications in chemistry over the past ten years. His article “Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites,”1 published in 1997 in Science, has exceeded the 5000 citations mark. With good reason: the 56-year-old German scientist, professor at the University of Strasbourg and researcher at CNRS’s Institut Charles Sadron (ICS),2 has sparked a small revolution in materials science: polyelectrolyte multilayers. Applied on surfaces, these piled-up molecular films (“millefeuilles moléculaires”) are capable of conferring new properties (catalytic, anticorrosive, anti-fouling, fire-retardant, antibacterial, and anticoagulating) to the materials they cover. against all odds Decher’s discovery is based on a wellknown principle described in all chemistry manuals: since the surface of most materials carries electric charges, they can bind molecules of opposite charge. The multilayer films described by Decher are stacks of oppositely-charged layers: positive, negative, positive... and so on. “Until the early 1990s, people were happy to adsorb monolayers and did not see the point in going any further,” explains the chemist. “Although never demonstrated, common sense suggested that any attempt to attach a second layer would dissolve the first one during deposition.” This did not deter the young researcher, then assistant professor at Johannes Gutenberg University Mainz, Germany. For two years, he optimized the first systems before finally achieving his breakthrough. His results were first met with skepticism from his peers, who believed them to be exceptions. “Yet on repeating the experiments, everyone obtained the same results,” recounts the chemist, who always described the experimental procedures in detail, so as to facilitate their reproduction. From there, the technology gave rise to a patent, filed with a German industrial consortium. Decher is no stranger to industry, since it was at Ciba Geigy AG (now Novartis) that he completed his postdoc in 1987. “I am fascinated by fundamental research, but I never lose sight of potential applications. This is a way to pay something back for the grants that I received,” he adds. Potential Unleashed When his contract in Mainz came to an end, he set out to find a permanent position and eventually settled at Louis Pasteur University in Strasbourg, in 1995. “I was willing to go anywhere, but Alsace was particularly attractive. The region’s biculturalism and proximity to Germany appealed to me and my family. My children are now bilingual,” he explains. It is within this university, at the ICS—specialized in macromolecules— that he set up his team (“Polyelectrolyte Multilayers”). His landmark article was published two years later. It covers LbL (Layer-by-Layer) deposition and describes the full potential of this technique, which can be used with an unprecedented choice of components such as proteins, DNA, or nanoparticles, thus paving the way for applications in biology, medicine, and materials science. Decher’s discovery makes it possible to “biocompatibilize” implants or to control the release of medicines by integrating the appropriate active molecules into multilayer assemblies. The inclusion of living cells should facilitate the development of artificial tissues. With far-reaching consequences, these findings triggered the interest of the scientific community. Fifteen years on, interest continues unabated in a subject covered by more than 1000 new articles in 2010—and over 300 dedicated research teams across the world. The first products using the LbL technique appeared in the early 2000s: contact lenses with hydrophilic LbL coatings and films that prolong the shelf life of fruits and vegetables (via the capture of ethylene, which accelerates ripening), the latest development being windows that reflect infrared light. Breaking the Speed Limit In a bid to find further applications, Decher also sought to scale up LbL production, especially by improving deposition speeds. Indeed, since each layer had to be dipped in a bath for several minutes, a 50-layer coating could take an entire day to produce. In 2005, Decher published a joint article in which he described how spraying can accelerate deposition more than a hundred-fold compared to dipping. Better still, it allows multilayer films to be applied on larger surfaces like car bodywork, for example, or windows. In 2010, the simultaneous spraying of two components speeded up the process further. Today, Decher and his team continue to focus on the fundamental issues of multilayer research, whilst exploring additional applications: nanofiltration membranes, conducting films, optical and magnetic devices, or the controlled attachment of cells. Multilayer films obviously have a bright future. 01. G. Decher et al., “Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites,” Science, 1997. 277: 1232-7. 02. Institut Charles Sadron (CNRS / Université de Strasbourg). Contact information: ICS , Strasbourg. Gero Decher > decher@ics.u-strasbg.fr 5 key dates 1956 Born in Marburg, Germany 1986 PhD in chemistry, on “Supramolecular systems,” at Johannes Gutenberg University Mainz, Germany 1994 A ssociate professor at Louis Pasteur University, Strasbourg, France 1997 Publication of the article “Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites” in Science 2009 E milia Valori Prize of the French Academy of Sciences “I am fascinated by fundamental research, but I never lose sight of potential applications.” © c . URBAIN


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