Confocal Raman microscopy of supercritical fluid dyeing of polymers

Abstract

Supercritical CO₂ was used as a medium to introduce azo-dyes into polymers (PMMA and PET). Confocal Raman microscopy has been applied using dry metallurgical and oil objectives to measure the concentration of dye as a function of distance from the surface to the core of the polymer samples. A significant gradient of dye concentration normal to the surface, down to the depth of ca. 100 µm, has been observed. In addition, cross-sections of cut dyed polymer samples have been analysed using a conventional mapping approach. The comparison between confocal depth and conventional mapping approaches has demonstrated that the use of the oil objective can provide reliable qualitative information on dye distribution in these systems. These confocal Raman experiments demonstrate the potential of this method in applications to polymeric materials processed with supercritical fluids.