Raman and FTIR studies of the distribution and dynamics of active molecules in polymer films.

Fourier Transform Infrared Attenuated Total Reflection Spectroscopy (FTIR-ATR) and Raman microscopy were employed to study the distribution and leaching of the fungicide fluorfolpet in plasticised poly(vinyl chloride) (pPVC) matrixes, along with the diffusion and perturbation of water molecules in the matrixes. Raman mapping and depth profiling were used to determine the molecular distribution of fluorfolpet on the surface and in the bulk of the films respectively. The films were examined both before and after treatment with water at 25°C, in order to study the effect of the leaching of fluorfolpet and its distribution and that of the plasticiser dioctylphthalate (DOP). It was found that the degree of leaching was strongly dependent upon the concentration of DOP in the films, and that leaching occurred from the surface (i.e. film/solvent interface). The distribution of the additives was determined to be "heterogeneous" on the microscopic scale, but "homogeneous" on the macroscopic scale. Additional information such as the rate of migration of the biocide inside the film was obtained using FTIR spectroscopy and the rotating disc method in conjunction with UV spectroscopy. FTIR-ATR was used to investigate the hydration and dehydration of plasticised PVC films. Monitoring of the time dependent change in the nu(OH) mode of water was used to determine the mode of sorption of water into PVC. A dual mode sorption model was found to fit the data well. Diffusion rates of water were found to be strongly dependent on the DOP concentration in the film. It was shown that the "free volume" and the "number of potential binding sites" were determining factors for the diffusion of water in PVC films. A systematic FTIR-ATR study of the perturbation of water sorbed into PVC polymer as a function of plasticiser content and time is reported. The nu(OH) band of water in the polymer has been fitted to individual components, corresponding to those recently found for pure water itself. A detailed quantitative analysis of the frequency shifts and relative intensities of these bands yields direct evidence for the breaking of the water network in the polymer matrix.