Atomic Force-, Confocal Laser Scanning-, and Scanning Electron Microscopy Characterization of the Surface Degradation of a Polymer

Changes of surface morphology of degradable polymers are currently characterized qualitatively by SEM. In order to study the degradation behavior of surface eroding polymers, the effective surface area should be quantified. Therefore, AFM and CLSM techniques were used to calculate the surface area of extruded films of (P(3HB-co-3HV)), used as a model and degraded in a bacteria culture for up to 95 hours. AFM and CLSM methods showed similar results at the beginning of degradation: the surface area decreased slightly during the first 6 hours of incubation time (2% mass loss) as biodegradation occurs preferably at places with a higher surface to volume ratio. Later on, the surface became rougher and both microscopy methods showed an increase of the surface area which reached a maximum after 30 to 47 hours of degradation (6 to 15% mass loss). The surface area measured with high resolution AFM showed an increase of about 54% while CLSM, having a lower resolution, showed an increase of about 26%. After 78 hours of degradation, (21% mass loss) no reliable measurements could be obtained anymore with AFM due to a too rough topography, while CLSM was not limited by surface roughness but by pore shape. The quantitative results regarding surface area correlated with qualitative SEM results and with the growth of the bacteria culture.