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 su ch surfaces. Here, we present new information on the surface enrichmen t of components from a biodegradable polymer blend composed of poly(se bacic anhydride) (PSA) and poly(DL-lactic acid) (PLA). This informatio n, derived by phase-detection imaging atomic force microscopy (AFM), d efines both the surface chemistry and morphology. We demonstrate that phase-detection imaging can distinguish between microdomains of PSA an d PLA in blends of these biodegradable polymers. Contrast between thes e two polymers is achieved even when the microdomains cannot be distin guished on surface topography images. The relationship between the for ce of tapping of the AFM probe on the polymer surface and the image co ntrast mechanism is investigated. In addition to detecting chemical an d mechanical variations on polymer blend surfaces, phase-detection ima ging can improve the resolution and contrast of images on single-compo nent films. This is demonstrated by the identification of lamellae wit h widths of less than 5 nm within PSA spherulites.