Editorial

Abstract

SIMS, as a non-destructive surface analysis technique for polymeric materials, started about 30 years ago; which happened co-instantaneously with the foundation of the journal Surface and Interface Analysis (SIA). Over the 30-year developments, SIMS has become one of the most important surface analysis techniques for polymeric materials owing to the combination of its unique capabilities: high molecular specificity, high surface sensitivity and sub-micrometer imaging resolution. In recent years, many advances have been made in the SIMS analysis of organic material surfaces such as molecular dynamics simulations, instrumental developments (e.g. cluster ion beams), data interpretation (e.g. multivariate analysis) and new methodology (metal-assisted SIMS). These advances have not only improved the SIMS capabilities for polymer analysis but also opened up new application perspectives. For example, it is now possible for some polymers to perform molecular depth profiles and construct 3D molecular images. Consequently, it seems timely and appropriate to gather research articles on the recent advancements of SIMS analysis on polymers into this special issue of SIA. The papers in this special issue are organized as follows. The volume starts with a concise and informative review by Delcorte et al. on their recent studies on the use of atomic and polyatomic ions in SIMS analysis of organic materials. The review covers both the theoretical study using molecular dynamics simulation and the experimental SIMS work and presents a nice overview on the progress on several areas such as molecular depth profiling, metal-assisted SIMS, molecular SIMS imaging. The strength and weakness of polyatomic versus atomic ion sources in these areas has also been critically assessed. The subsequent paper by Piwowar and Vickerman systematically studies the effects of molecular weights on the ToF SIMS spectra of poly(methyl methacrylate) (PMMA) when Au+ and C60+ are used as primary ions respectively. Their results have clearly shown that the C60+ ion source produces much higher secondary ion yields than Au+ ion source and the ion yield enhancements are consistent across the entire investigated molecular weight range. Three papers in this special issue are focused on the depth profiling of polymers. The paper by Mahoney presents a thorough investigation of the effect of polymer stereochemistry on depth profiling. Three stereo-specific PMMA samples (isotactic, atactic and syndiotactic) were depth profiled using SF5+ polyatomic ion source at different temperatures and the damage characteristics of these samples were compared. The results clearly showed that a polymer's physical properties also play an important role in molecular depth profiling. The paper by Houssiau and Mine provides a detailed investigation on the feasibility of molecular depth profiling of PMMA, polycarbonate (PC) and polystyrene (PS) using low energy (250 eV) Cs+ and Xe+ ions. All the three polymers can be successfully profiled using Cs+ but not all by Xe+. These results allowed the authors to point out the special beneficial effects of low energy Cs+ in polymer depth profiling, namely the negative ion signal enhancement and the inhibition of cross-linking reactions due to Cs reactivity. Finally, the paper by Lee et al. presents a nice application of ToF SIMS depth profiling using Cs+ and C60++ to a polystyrene-poly(n-propyl methacrylate) diblock copolymer system. Their results clearly showed that the microstructure changes of the copolymer due to annealing temperatures and times are reflected in the SIMS profiles. The last three papers in this special issue provide real applications of SIMS in combination with XPS to different polymeric materials. Baytekin et al. showed how the combination of ToF SIMS and XPS can be used to provide full surface chemistry and wettability of micro-fluidic devices and to monitor the effectiveness of their processing. On the other hand, Shimizu et al. have used ToF SIMS and XPS to study the interfacial interaction between polymeric methylene diphenyl diisocyanate (PMDI) and aluminum. Their results clearly showed that the reaction of PMDI with water can be quantitatively followed by ToF SIMS and XPS and a covalent bonding between PMDI and aluminum was unambiguously proven from ToF SIMS results. Finally, the paper by Lau et al. demonstrated that the surface composition changes of liquid crystalline polymers as a result of molecular ordering can be easily monitored using ToF SIMS combined with principal component analysis.