Structural Changes in Surface-Modified Polymers for Medical Applications

Biological properties of synthetic polymers can be improved by surface modification with the use of liquid oxidizers. A resorbable biomedical polymer - poly(glycolide-co-ε-caprolactone) (PGCL) was incubated in 0.1 M NaOH for 2, 6, 16, and 24 h, followed by excessive washing and drying in vacuum. Surface properties of the materials before and after modification were evaluated: wettability by contact angle measurements, topography by atomic force microscopy, and chemical functions by infrared spectroscopy. Applied modification improved wettability of PGCL due to creation of chemical oxygenated functionalities, and resulted in a slight alternation of the surface topography and roughness. In order to determine whether NaOH incubation caused structural changes in bulk of PGCL, positron annihilation lifetime spectroscopy, differential scanning calorimetry and viscosity measurements were performed. It was found that the ortho-positronium lifetime in PGCL declines as a function of modification time. It suggests that NaOH incubation causes structural changes in PGCL not only on the surface but also in bulk.