Initiation of chemical reactions at polymer-polymer interfaces.

The development of new polymer composites is largely based on knowledge of the interaction between the different materials within the boundary layers. A prerequisite for stable composite or hybrid formation is a permanent bond between the different polymer materials. Not only chemical bonds, especially covalent bonds, but also physical interactions cause durable adhesion and resilient materials or components.

The research goal is to create a strong bond between two or more polymer materials by triggering chemical coupling reactions locally in the interfaces. The local heating of the interface is achieved by induced eddy currents. This is generated by placing metal particles in the interface between the materials to be coupled and then exposed to very short high-field magnetic pulses. When the activation energy is exceeded, the formation of covalent bonds between the polymers is stimulated. A thermal load on the bulk polymers remains low, since only the interface heats up locally.

"Cold" boundary layer reaction

• Low-interaction transfer of energy into the interior of the material.
• Initiation of chemical reactions.
• Processing without heating the bulk volume.
• Processing of bio- or renewable macromolecules. Low stresses in the material interfaces, as material class-dependent shrinkage is suppressed after heating.

Biopolymers or biopolymer composites are preferable to polymer materials made from fossil raw materials from the point of view of environmental compatibility and sustainability. When using composites or hybrid technology, the interfacial layers make a decisive contribution to the material properties. Targeted interfacial engineering and powerful analytical methods are decisive.

For thermally unstable biopolymers or those stabilized by hydrate shells, conventional processing at high temperatures is impossible. Heating the volume for processing leads to irreversible destruction of the molecular structures. The goal must be to apply the processing energy specifically at the interfaces. Without process-related interaction with the bulk material, undesirable processes such as discoloration, shrinkage or chain degradation do not occur. This is referred to as using processes to initiate "cold" interfacial reactions.

Chemical coupling in magnetic high fields

Magnetic high fields with field strengths greater than 70 T are used at low frequency to introduce energy into the interfacial layers. Applications, e.g. chemical bonding/debonding of thermolabile materials, such as hydrogels or biopolymers, are also conceivable as solid phase transformations.

Electromagnetic high-frequency fields for triggering chemical reactions

If electromagnetic transducers are placed in the boundary layer, localized energy absorption of a high-frequency electromagnetic field can be achieved. Applications include chemical interfacial reactions or chain scissions that create a second internal phase in the material, chain growth, or crosslinking of biopolymers at solid-liquid interfaces.