Degradation of poly(acrylates) under SF5+ primary ion bombardment studied using time-of-flight secondary ion mass spectrometry. 1. Effect of main chain and pendant methyl groups

Abstract

Polyatomic primary ions have been applied recently to the depth profiling of organic materials by secondary ion mass spectrometry (SIMS). Polyatomic primary ions offer low penetration depth and high damage removal rates in some polymers, but the relationship between polymer chemistry and degradation under polyatomic primary ion bombardment has not been studied systematically. In this study, positive and negative ion time-of-flight SIMS (ToF-SIMS) was used to measure the damage of ∼100 nm thick spin-cast poly(methyl methacrylate) (PMMA), poly(methyl acrylate) (PMA) and poly(methacrylic acid) (PMAA), films under extended (∼2 × 1014 ions cm−2) 5 keV SF5+ bombardment. These polymers were compared to determine the effect of the main chain and pendant methyl groups on their degradation under SF5+ bombardment. The sputter rate of PMMA was approximately twice that of PMA or PMAA and the rate of damage accumulation was higher for PMA and PMAA than PMMA, suggesting that the main chain and pendant methyl groups played an important role in the degradation of these polymers under SF5+ bombardment. These results are consistent with the literature on the thermal and radiation-induced degradation of these polymers, which show that removal of the main chain or pendant methyl groups reduces the rate of depolymerization and increases the rate of intra- or intermolecular cross-linking. Copyright © 2004 John Wiley & Sons, Ltd.