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University of Konstanz – crystallinity is key

Renewable resources not only provide the field of biotechnology with interesting possibilities for the development of new materials. Scientists from the Department of Chemical Material Science at the University of Konstanz have now succeeded in chemically synthesising a new type of plastic from plant oils.

A new type of plastic made from plant oils. © University of Konstanz

The Department of Chemical Materials Science at the University of Konstanz headed up by Prof. Dr. Stefan Mecking focuses on the generation of polymers and nanoparticles using catalytic methods as well as the development of new catalysts. "Our particular focus is catalysts that continue to work in the presence of functional groups. This is an important aspect because catalysts are frequently deactivated by functional groups," said Prof. Dr. Stefan Mecking whose department specialises in the generation of new materials from renewable resources.

Whilst working towards her doctorate in Mecking's department, Dorothee Quinzler developed a new type of plastic from plant oils. In contrast to previous methods which cleave the double bond of fatty acids, Quinzler's new polyester production method involves the complete transfer of unsaturated fatty acids into the polymer. "It was not previously possible to produce aliphatic polyesters of this kind, as long-chain dicarbonic acid monomers were not available," said Prof. Mecking. The researcher's method of synthesising polyester from plant-derived unsaturated fatty acids using isomerising carbonylation is an interesting alternative to established biotechnological plastics production methods. Although carbonylation methods have been used on a large scale for quite a while, it will still take some time before researchers will be able to use this method on the new polyester. "Our prime goal is to improve the catalysts; once we have succeeded in doing this, we will be able to work on large-scale carbonylation," said Mecking.

High degree of crystallisation

“As plant oils are difficult to obtain, it was essential to find a way to use the oils to synthesise high-quality products with a specific property profile,” said Prof. Mecking. The polyesters synthesised by Prof. Mecking’s team have a relatively high melting point because they are very crystalline. “The polyesters’ crystallinity is caused by van der Waals interactions occurring between neighbouring linear chains,” Mecking explains. It is far more difficult to crystallise polyesters with branched polymer chains. The degree of crystallisation affects the thermal and chemical properties of the polymer and its field of application. However, the property profile of the new plastic has not yet been fully explored. “Although we have not yet been able to prove that the polyester is biologically degradable, we nevertheless assume that this is the case,” said Mecking. The scientists also believe that it will be possible to use the new plastic as a technical plastic. The researchers’ next goal is to produce larger quantities of the plastic and further clarify its property profile in order to subsequently test the application of the polyester in cooperation with industrial partners. The investigations are being funded by the Baden-Württemberg Foundation under the “Environmental Technology Research” programme.

Fluorescent nanoparticles in medicine

Another issue the Konstanz researchers are working on is the production of nanoparticles. The researchers will initially be focusing on the melting and crystallisation properties of polymeric nanocrystals. “Previously it was impossible to produce freely movable polymer nanocrystals,” said Mecking. Such nanocrystals can be used to produce very thin films, for example hydrophobic coatings. In addition, the department also deals with hybrid nanoparticles with an organic and inorganic phase. “The organic shell helps to adapt the properties of the inorganic particles to their environment,” said Mecking explaining that this might relate to the specific reactivity to the binding or protection of the cores. This project is part of a collaborative research centre (SFB), which also involves the Department of Modern Optics and Quantum Electronics headed up by Prof. Dr. Leitenstorfer.

Fluorescent nanoparticles have major potential for use in the field of medicine. “Our initial goal was to produce fluorescent nanoparticles whose spectrum was easy to adjust,” said Mecking. Thanks to the efficient transfer of energy from the polymer to a dye, only small amounts of dye are necessary. The fluorescent dyes that are covalently bound inside the nanoparticles were visualised using 2-photon microscopy and monitored in living cells. Fluorescence might be used to monitor the path of nanoparticles through the body. Although nanotechnology provides excellent opportunities for application in environmental and health technology, it is still associated with risks that are somewhat difficult to assess at the current time.

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