Magnetic high field pulses can be applied to initiate cold and interfacial reactions. The initiation of the chemical reaction is triggered in a volume, which is limited to cubic nanometer range. The initiation of the reaction is named a cold one, because the bulk material has not been heated to put in the activation energy. At first, magnetic high field pulses induce an eddy current in metallic structures (susceptors), which are localized within the interface of reactive materials. After generation, eddy currents are converted to heat. The resulting thermal energy exceeds the activation energy necessary to couple two reactive materials surrounding the susceptors. The coupling process is particularly suitable for the permanent bonding of plastics (Bisphenol-A based polycarbonate (PC)) with thermally unstable materials (polyvinylamine (PVAm)) or especially with hydrogels. The resulting interface layers in the formed hybrid material are characterized and only few nanometers thick. The molecular interfacial layer analysis is a prerequisite for a targeted process development and contains the information about the newly formed covalent bonds. To determine the properties of the interface in relation to the bulk is challenging. It is often below the limit of detection of established analytical methods. The characterization of reactive interfaces, therefore, requires a combination of polymer analytical methods. Metallic-nanoparticle-based interfacial enhanced infrared spectroscopy, scanning electron microscopy, transmission electron tomography, thermal analysis and gel permeation chromatography were combined or adapted. Model systems are used to explain the reaction mechanism and the adhesion properties by their adhesive and non-adhesive contributions.