Thermally Induced Cross-Linking of Polymers via C,H Insertion Cross-Linking (CHic) under Mild Conditions

The focus of studies performed so far on the formation of surface-attached polymer networks by C,H insertion cross-linking (CHic) reaction has been largely on photochemical activation. This study describes the thermal activation of the formation of (surface-attached) polymer networks under comparably mild conditions. A novel cross-linker, based on a diazo phenyl ester group, is incorporated into various copolymers, which are subsequently deposited on solid substrates. Upon activation, the cross-linker moieties generate carbene intermediates, which lead to rapid, complete cross-linking of the whole film and simultaneous surface attachment to various organic materials via CHic. Although this system requires only comparably mild conditions (i.e., below 100 degrees C) to become activated, a long shelf life at room temperature is observed. The presented system might be useful in a wide range of applications, from coatings to rather complex geometries. We demonstrate the covalent binding of protein-repellent thin films to the inner surface of (rubber) tubes and the generation of patterned structures by a branding iron approach. For this a hot structure is pressed onto a diazo polymer coated surface, leading in the contact zone to fast cross-linking while in all other areas the polymer remains soluble and is washed off during subsequent extraction.

Automated summary

This study focuses on the thermal activation of surface-attached polymer networks under mild conditions, using a novel cross-linker based on a diazo phenyl ester group. The system, which enables the rapid complete cross-linking of films with simultaneous surface attachment to organic materials via CHic, only requires activation below 100 degrees C and has a long shelf life at room temperature. It has potential applications in coatings and complex geometries.