Infrared and X-ray photoelectron spectroscopy of aminophenyltrimethoxysilane films on metals

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Abstract
The molecular structures of thin films formed by aminophenyltrimethoxysilane (APTMS) deposited onto mechanically polished aluminum, iron, and copper substrates from dilute aqueous alcohol solutions were determined using reflection-absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). The as-deposited films on all three substrates were similar and consisted of hydrolyzed oligomers that condensed to form siloxane polymers during heating at elevated temperatures. APTMS films on all three substrates reacted readily with epoxy resins at 150°C. Although some loss of nitrogen was observed, the films formed on aluminum were relatively stable during heating at 250°C and inhibited oxidation of the substrate. The films formed on iron and copper depolymerized rapidly during heating at 250°C and failed to inhibit oxidation of the substrates. It was concluded that APTMS films were potentially useful primers for use at high temperatures on aluminum, but not on copper or iron.