Phase Separation at the Surface of Poly(ethylene oxide)-Containing Biodegradable Poly(l-lactic acid) Blends

摘要

The surface chemistry and in-depth distribution of the composition of a poly(ethylene oxide) (PEO)-containing biodegradable poly(l-lactic acid) (PLLA) blend matrix system have been investigated using X-ray photoelectron spectroscopy (XPS). This study reports detailed quantitative compositional information using a novel numerical method for determining depth profiles. The PEO system studied is an amphiphilic Pluronic P104 surfactant, PEO–b-poly(propylene oxide) (PPO)–b-PEO. The extent of phase separation is analyzed by determining the surface enrichment of the PEO component via measurement of chemical composition at the polymer–air interface. For this blend system, the combination of the PPO component in the Pluronic surfactants drives the formation of a surface excess of Pluronic in the blends with PLLA. The surface excess profile shows a rapid increase in Pluronic surface composition versus bulk Pluronic mass fractions of 1–5%, but the profile levels off above bulk Pluronic mass fractions of 5%.