BioBond

In order to achieve the necessary adhesion under consideration of economic aspects, a combination of the structural advantages of lignin from lignified plants and an imitation of the adhesion force that can be achieved by mussels on smooth surfaces is planned.

Lignin forms the structural basis of green plants and trees. On the basis of its complex three-dimensional polymeric structure, the other plant components cellulose and hemicellulose are combined in an extremely load-bearing construction. The underlying lignin can be obtained from renewable raw materials or residual materials, making the starting material CO2-neutral. Furthermore, the combination of a natural wood component with a frequently occurring amino acid provides a harmless adhesive.
In this way, a new biomimetic adhesive can be developed which consists mainly of plant residues. A particular advantage of the new material is its biodegradability, which makes recycling by "composting" with ligninolytic enzymes or fungi possible.

Despite the fact that lignin can in principle be used as an adhesive, the material cannot compete with technical petrochemical derivatives. This is particularly due to the low adhesion to smooth surfaces. For this reason, a combination of the lignin structure with the primary component of mussel adhesives, 3,4-dihydroxyphenylalanine (DOPA), is planned. Here, a biocatalytic coupling of the amino acid DOPA with the heteropolymer lignin is pursued. There is a structural similarity between the two components, so that chemical binding to the surface of the lignin can be easily carried out. DOPA shows very good adhesion properties, especially on metal oxide compounds. By combining the two materials, two successful natural binders can be used in a biomimetic way to create a new biodegradable adhesive.

One target application of the new adhesive is the Bioconcept-Car of the project partner FOUR MOTORS GmbH. The current Bioconcept-Car, a Porsche Cayman GT4 Clubsport, is a pioneer for a new fuel generation, the E20 - a petrol with 20 percent bioethanol additive. Furthermore, parts of the racing car consist of a bio-polymer reinforced with natural fibres.
This is where the planned research project will start, both for the combination of bio-based plastics and metallic joining partners.