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On Soft Matter FASCINATING Research Soft MATTER Hard Work on Soft Matter What do silk blouses, diskettes, and the membranes of living cells have in common? All three are made barked on an unparalleled triumphal between the ordered structure of building blocks.“ And Prof. Helmuth march. Even information, which to- solids and the highly disordered gas. Möhwald, director of the “Interfaces” from soft matter: if individual molecules are observed, they appear disordered, however, on a larger, day frequently tends to be described These are typically supramolecular department at the MPIKG adds, “To as one of the most important raw structures and colloids in liquid me- supramolecular scale, they form ordered structures. Disorder and order interact, thereby affecting the put it in rather simplified terms, soft materials, can only be generated, dia. Particularly complex examples matter is unusual because its struc- properties of the soft material. At the MAX PLANCK INSTITUTES FOR POLYMER RESEARCH stored, and disseminated on a mas- occur in the area of biomaterials,” ture is determined by several weaker sive scale via artificial soft materials. says Prof. Reinhard Lipowsky, direc- forces. For this reason, its properties in Mainz and of COLLOIDS AND INTERFACES in Golm, scientists are focussing on this “soft matter”. Without light-sensitive coatings, tor of the “Theory” Division of the depend very much upon environ- there would be no microchip - and Max Plank Institute of Colloids and mental and production conditions.” nor would there be diskettes, CD- Interfaces in Golm near Potsdam The answers given by the three ROMs, and videotapes, which are all (MPIKG). Prof. Hans Wolfgang scientists are typical in that their made from coated plastics. Spiess says, “Soft material reveals its perspectives all differ. Some scien- It is nature, however, which has complex combinations of properties tists define soft matter as being al- really perfected the art of creating due to the precise interplay between most liquid, whilst others also in- soft matter. For billions of years, areas of order and disorder of the clude very strong materials such as natural or artificial fibres. However, whether liquid or solid – there are properties that all forms of soft ma- terials have in common. What the three scientists have outlined in Hans Wolfgang Spiess with the probe-head of a NMR spectrometer (in the background) Klaus Müllen also achieves mastery over polymers in the form of a football… he cultural development of since the existence of life on earth, „T mankind is inseparably linked highly complex structures have orig- to the development of new, high- inated from soft matter. The ways in performance materials,” says Prof. which they arise are typically very Hans Wolfgang Spiess, Managing elegant; the molecules organise Director of the Max Planck Institute themselves into complex cellular for Polymer Research in Mainz; “it is membranes which perform vital not without reason that we speak of functions. Or they form extremely the Stone, Bronze or Iron Age.” After strong fibres that give plants shape this hard prehistoric past, we have and support. Biologists, chemists, now arrived in the age of soft mat- material scientists, and physicists are ter: leather and natural fibres such trying to understand and emulate ILSER as wool and silk or paper have been F nature’s incredible structures and important economic commodities for OLFGANG production processes. centuries. And over the past fifty : W “The term soft material relates to HOTOS years, synthetic materials have em- P the states of aggregation which lie 52 M AXP LANCKR ESEARCH 4/2001 4/2001 M AXP LANCKR ESEARCH 53 FASCINATING Research Soft MATTER technical terms (explained on page tremendous variety of polymers. The Despite the simulation being virtual, excited by an NMR spectrometer to 60) can be roughly expressed in lay- carriers of the hereditary informa- they are able to zoom into the mole- receive and transmit electromagnetic man’s terms as follows: tion of life, the nucleic acids, are cular processes that take place in re- signals. From this, the scientists are ❿ Firstly, the molecules form a polymers. Proteins are polymers, as al polymers. able to deduce how the material is much more disordered structure in is the starch from potatoes or grains. For the computer simulations to be constructed. Spiess and his col- soft matter than the atoms or mol- Polymers also lend animal tissue able to draw a realistic picture of the leagues have developed new solid ecules in the crystal lattice of a elasticity and stability in the form of material being studied, they must al- state NMR methods, which are par- true solid. On the other hand, they Fig. 1: This three-dimensional collagen fibres. Other polymers, cel- so be provided with reliable data ticularly suitable for explaining the do not swirl around in a disor- At the Max Planck Institute for “snapshot” from a Mainz computer lulose fibres, perform this function from measurements in order to have structure of polymer materials. simulation shows how the long dered fashion as they do in a gas. Polymer Research in Mainz, the sci- in plant tissue. firm ground to stand on. This data is By working with the theorists and polymer chain molecules move in Soft materials are also not true liq- entists are investigating a type of a polymer melt. In Mainz, two research groups are being provided by the “Polymer spectroscopists, the material scien- uids, although areas that are liquid soft material without which life – playing a special role in the analysis Spectroscopy” research group under tists in Mainz are able to experiment can affect their properties signifi- and our everyday existence as we of the properties of polymers. They Hans Wolfgang Spiess. Spectroscopy very effectively. Besides, pure re- cantly. know it today – would be unimagin- are developing increasingly precise is the second tool for the developer search, applied research – the aim of ❿ Secondly, the structures of soft able: natural and artificial materials instruments which allow them to of new materials. This is where the which is to develop marketable prod- matter are both flexible and stable. consisting of polymers. Polymers are look into the world of molecules. new samples are investigated using ucts – is also important at the Mainz ESEARCH ❿ Thirdly, soft matter can form large molecules in which hundreds R Thanks to these tools, the researchers various analytical methods. NMR Institute. The scientists at Mainz are supramolecular structures sponta- or thousands of similar, fundamental OLYMER in the laboratories are far better able (Nuclear Magnetic Resonance) spec- even able to further develop conven- P neously through self-organisation. building blocks, the monomers, are FOR to understand the properties of the troscopy is particularly important. tional mass-produced plastics so that Without this particularly interest- strung together. Every artificial ma- polymer molecules. They are in a NMR makes use of the fact that they get completely new properties; .: MPI IG ing characteristic, no natural or- terial, from the contact lens to the F much better position to investigate many atomic nuclei behave like tiny for example, pipes made from poly- ganism would be able to exist or most modern woven fibre, is a poly- Fig. 2: The pushed-in repair tube materials and develop new ones with magnets. Placed in a strong magnet- ethylene, the artificial material from survive. mer. Nature conceals an even more before inflation. greater accuracy than previously. ic field, these atomic magnets can be which plastic bags are made. One successful example of indus- trial co-operation by the Max Planck Institute for Polymer Research is the development of an artificial material Joachim O. Rädler is head of the polymer physicists in Mainz. His group is for renewing pipes in collaboration studying the interaction between molecules in order to use them for building nano-systems, and is hot on the trail of nature’s fascinating strategies, one of which is the self-organisation of molecules into complex structures. Kurt Kremer is head of the Theory Division in Mainz. One of these tools is computer simulation. The experts in this area are members of the “Theory of Poly- mers” research group, headed by one of the Institute directors, Prof. Kurt Intact material Formation of cracks Kremer. The scientists construct the simulated polymer material from in- dividual, virtual molecules and cal- culate its properties. Soft matter is still too complex to be easily repro- duced in all its detail on a computer. But the theorists are able to simulate Partially crystalline polymer the most important properties amaz- ingly well (Fig. 1). In the process, Fig. 3 left: The long chain molecules they are learning how the individual (red) hold the crystalline (blue) together in the undamaged plastic. molecules behave in the polymer. Right: Under stress the chains 54 M AXP LANCKR ESEARCH 4/2001 tear and a crack opens. 4/2001 M AXP LANCKR ESEARCH 55 Fig. 4: Dumbbell-shaped graphite FASCINATING Research islands arrange themselves on a Soft MATTER graphite surface. Two neighbouring islands are approximately 3 nm away from each other. with a subsidiary of the former to the Max Planck Society’s annual great pressure. As it must not deteri- the crystallites. The industry is now dumbbell or a figure of eight. Fig. 4 Hoechst Corporation. Who hasn’t budget”, Hans Wolfgang Spiess men- orate with time over decades, flexi- using the modified plastic to produce shows the regular pattern formed by had big problems with pipes at one tions in passing. bility creates a problem. Flexibility new, flexible pipes with a life up to these islands on the surface. time or another? And not just with does in fact depend on high mobility fifty times longer than before. Now the island structures develop HIGH-TECH-PLUMBERS ceramic or metal pipes: plastic pipes of the molecules in the artificial ma- It may be that soft materials of the remarkable behaviour: they stack can also crack or become porous.
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