Studying interfacial bonding at buried polymer–zinc interfaces

• Buried interfaces of carboxylic polymers and Zn surfaces are studied.
• Reaching buried interfaces by analytical techniques is challenging.
• Buried interfaces can be mimicked by adsorption of representative molecules.
• Buried interfaces are also evaluated by studying polymer covered thin metal films.
• Surface chemistry, roughness and semiconductor properties are key factors.

This manuscript is a critical appraisal of our recent studies on the possible parameters influencing the interfacial bonding properties between carboxylic polymers and Zn surfaces as well as approaches to effectively understand interfacial phenomena. It has been shown that different surface pretreatments result in a set of ranging chemical compositions, morphologies, roughnesses and semiconductor properties, while each parameter in turn influences the interfacial properties. Moreover, polymer functional groups available for interfacial interactions effectively influence the interfacial phenomena. To overcome the limited analytical depths of the available spectroscopic techniques to study underneath thick polymer coatings, i.e. buried interfaces, several approaches are examined in this study. Polymer and metal interfaces are modeled by adsorption of the representative functional molecules forming thin semi-monolayers on the metal surface. Towards understanding the real polymer and metal interactions, polymer coatings were mechanically removed from the metal surface and residue layers were shown to exhibit the metal and polymer interface. Moreover, interfaces were analyzed by means of Kretschmann geometry in which a thin metallic substrate was deposited on an internal reflection element. In this case, an electric filed passes the metallic substrate and reaches the metal and polymer interfaces. Both formation and degradation of the interfacial bonding in dry and wet conditions were analyzed respectively. The later case was integrated with electrochemical impedance spectroscopy to obtain a thorough understanding of the ongoing polymer degradation and interfacial electrochemical interactions.