Application of matrix-assisted laser desorption/ionization mass spectrometric imaging to monitor surface changes of UV-irradiated poly(styrene) films.

This study presents the application of matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI) to monitor changes occurring at polymer surfaces. As an example, a poly(styrene) (PS) film was irradiated with ultraviolet (UV) light at 254 nm for different time intervals, while areas of the film were protected from UV light by covering it with an aluminum mask. After the UV treatment, the polymer surface was analyzed by MALDI-MSI. Time-dependent photo-induced cross-linking of the polymer film was observed, and a correlation curve between UV radiation time and area of cross-linking was constructed. This represents the first step towards the surface analysis of polymer components of photoresists and top coatings of cars, and it will also enable a new characterization strategy for combinatorial material research.