Evaluation of monolayers and multilayers of phenylene sulfide oligomers on metal surfaces using TOF-SIMS and AFM

We attempted to evaluate the interaction between metal and polyphenylene sulfide (PPS), and especially metal–sulfur bonding, by using time‐of‐flight secondary ion mass spectrometry and atomic force microscopy. As model PPS compounds, two kinds of phenylene sulfide oligomer—a tetramer and a heptamer—were synthesized and their monolayers and multilayers were formed on Ag, Cu, and Al substrates. Comparison of the monolayers with the multilayers revealed that, in the case of the tetramer, the monolayers formed uniformly on all substrates and metal–sulfur bonds were present. The Ag–sulfur and Cu–sulfur bonds were stronger than the Al–sulfur bond. In contrast, with the heptamer, the molecular interaction was stronger than that with the substrates, and consequently the sulfur atoms did not contact the metals. Therefore, the monolayers barely formed on all substrates. These results indicated that the larger the oligomer, the weaker the metal–sulfur bonding; this is one of the reasons why it is difficult to join PPS to metal directly. Copyright © 2012 John Wiley & Sons, Ltd.