Delamination Kinetics of Thin Film Poly(acrylate) Model Coatings Prepared by Surface Initiated Atom Transfer Radical Polymerization on Iron

Abstract

Living radical polymerization is often considered as an unsuitable method of surface modification for reactive metals such as iron. Necessary noble metal catalyst systems may react with the surface to be modified, causing deactivation of the catalyst. Here, surface-initiated atom transfer radical polymerization (SI-ATRP) using the typical CuI-based catalyst was used to synthesize well-defined poly(methyl methacrylate) thin films grafted on iron. Alkoxy- and chloro-silane initiators were anchored to the metal surface via Si-O-Fe bonds in a metal pretreatment step, yielding a thin cross-linked multilayer sol/gel coating. Except for the precursor’s leaving group, the resulting 10s of nm thick polymer layers were almost identical. Assessment of the delamination kinetics of the model coatings by scanning Kelvin probe (SKP) showed the average delamination to be ≈ 40 % lower in the systems with alkoxy-precursor compared to those with chloro-precursor. In addition, the spread of the measured delamination rates decreased to 1/3 in the alkoxy system, despite identical polymers. The higher delamination rate in the case of chloro-precursors was attributed to residual chloride at the interface. Initiator surface coverage differences may also contribute to stability differences. The ATRP-CuI-catalyst is consequently also suitable for surface modification of non-noble metals after appropriate pretreatment.