Raman and Infrared Microspectroscopic Mapping of Plasma-Treated and Grafted Polymer Surfaces

Abstract

The grafting of polystyrene (PS) onto a predominantly polypropylene (PP) substrate has been followed by Raman and infrared microspectroscopic mapping. For exactly the same 50 μm × 50 μm section of polymer surface, Raman spectra were obtained at 1 μm intervals for the substrate, the surface after plasma treatment, and the surface after PS grafting. Maps of the substrate were constructed, indicating the crystallinity variation across the surface and also the distribution of the minor component ethylene-propylene rubber (EPR). After plasma treatment, the crystallinity was found to decrease slightly. Infrared microspectroscopic maps of a larger plasma-treated surface were also obtained with the technique of attenuated total reflection. The spatial resolution of these maps was 50 μm, and they showed the distribution of the hydroxy groups introduced onto the surface by the plasma treatment. PS grafting was found to be heterogeneous. Increased concentrations of grafted PS showed some correlation with positions on the surface which had higher EPR after plasma treatment.