Surface characterization of butyl methacrylate polymers by XPS and static SIMS

Abstract

Abstract X‐ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SIMS) were used to identify and quantify different isomeric butyl methacrylate polymers. The samples examined were normal‐, iso‐ and tert ‐ butyl methacrylate ( n ‐, i ‐ and t ‐BuMA) homopolymers and two n / t ‐BuMA random copolymers. XPS could differentiate the various BuMA polymers based on their valence band (VB) lineshapes. Resolution of the C 1s spectra into four Gaussian peaks (hydrocarbon, β‐shifted hydrocarbon, ether and ester) produced similar peak widths and good agreement between the resolved peak areas and the polymer structure. Because of the C 4 carbonium ions formed, static SIMS can distinguish the BuMA homopolymers by the increase in the m / z = 57 + signal (C 4 H 9 + ) from n ‐BuMA to i ‐BuMA to t ‐BuMA. For the n / t ‐BuMA random copolymers, the amount of dehydrogenated C 4 groups produced by static SIMS experiments (positive 55 and negative 71 ions) increased with increasing n ‐Bu concentrations. Any one of several peak intensity ratios (positive 55/57 and 57/69 and negative 57/85 and 71/85) can be used to determine the percentage of n ‐BuMA and t ‐BuMA components present in an n / t ‐BuMA copolymer. A combination of two different peak intensity ratios is required to distinguish the i ‐BuMA polymer from an n / t ‐BuMA copolymer. The clearest differentiation of the BuMAs was obtained by combining XPS VB and static SIMS results.