Degradation of poly(acrylates) under SF 5 + primary ion bombardment studied using time‐of‐flight secondary ion mass spectrometry. 2. Poly( n ‐alkyl methacrylates)

Polyatomic primary ions offer low penetration depth and high damage removal rates in some polymers, facilitating their use in the molecular depth profiling of these polymers by secondary ion mass spectrometry (SIMS). This study is the second in a series of systematic characterizations of the effect of polymer chemistry on degradation under polyatomic primary ion bombardment. In this study, time‐of‐flight SIMS (ToF‐SIMS) was used to measure the damage of ∼90 nm thick spin‐cast poly(methyl methacrylate), poly( n ‐butyl methacrylate), poly( n ‐octyl methacrylate) and poly( n ‐dodecyl methacrylate) films under extended (∼2 × 10 14 ions cm −2 ) 5 keV SF 5 + bombardment. The degradation of the poly( n ‐alkyl methacrylates) were compared to determine the effect of the length of the alkyl pendant group on their degradation under SF 5 + bombardment. The sputter rate and stability of the characteristic secondary ion intensities of these polymers decreased linearly with alkyl pendant group length, suggesting that lengthening the n ‐alkyl pendant group resulted in increased loss of the alkyl pendant groups and intra‐ or intermolecular cross‐linking under SF 5 + bombardment. These results are partially at variance with the literature on the thermal degradation of these polymers, which suggested that these polymers degrade primarily via depolymerization with minimal intra‐ or intermolecular cross‐linking.