Investigation of the water-induced reorganization of polycaprolactone-poly(fluoroalkylene oxide)-polycaprolactone triblock copolymer films by angle-dependent X-ray photoelectron spectroscopy

The water-induced reorganization of a series of poly(caprolactone)-poly(fluoroalkylene oxide)-poly(caprolactone) (PCL-PFPE-PCL) thin film surfaces was studied by angle-dependent X-ray photoelectron spectroscopy (XPS). The reorganization was studied as a function of polymer chain length, water exposure time, and XPS sampling depth. The prepared films were exposed to water and then frozen in liquid nitrogen to preserve the surface composition during XPS analysis. The XPS results showed the PFPE block segment length influenced the extent and rate of segment reorganization at the surface. The detected changes were shown to be reversible upon re-exposure to air and the effect of liquid-nitrogen freezing was determined to be negligible.