Chemical and morphological analysis of surface enrichment in a biodegradable polymer blend by phase-detection imaging atomic force microscopy

Surface enrichment phenomena are important in determining the surface organization of fabricated biomaterials and other polymeric materials. Enrichment can govern both the surface chemistry and morphology of such surfaces. Here, we present new information on the surface enrichment of components from a biodegradable polymer blend composed of poly(sebacic anhydride) (PSA) and poly(DL-lactic acid) (PLA). This information, derived by phase-detection imaging atomic force microscopy (AFM), defines both the surface chemistry and morphology. We demonstrate that phase-detection imaging can distinguish between microdomains of PSA and PLA in blends of these biodegradable polymers. Contrast between these two polymers is achieved even when the microdomains cannot be distinguished on surface topography images. The relationship between the force of tapping of the AFM probe on the polymer surface and the image contrast mechanism is investigated. In addition to detecting chemical and mechanical variations on polymer blend surfaces, phase-detection imaging can improve the resolution and contrast of images on single-component films. This is demonstrated by the identification of lamellae with widths of less than 5 nm within PSA spherulites.