Prediction of Surface Segregation of Fluorinated Additives from Measurement of Wettability Properties of...

The aim of this work is to describe the segregation phenomenon of random perfluorinated copolymers toward the surface of a polystyrene (PS) matrix. Three random perfluorinated copolymers, named POISE-a (Polymer prOcessing Interface StabilizEr), synthesized with different amounts of chemically bound fluorine, were mixed with a commercial PS matrix by a solvent casting process. Their effect on the wettability properties of PS as a function of their concentration was measured first under static conditions with different liquids (water, formamide, diethylene glycol) and then under dynamic conditions with water. The evolution of the cosine of the static and dynamic advancing contact angles as a function of the fluorine content by weight in the bulk was predicted using an original physical law, in which the different parameters were related to the morphology of the additivated polymers as revealed by experimental X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy-energy dispersive X-ray (SEM-EDX) measurements. This law has been successfully used to predict the wetting properties of other polymer blends and has contributed to a better understanding of the phase segregation mechanism of additives migrating to the PS surface, at the origin of the increase in hydrophobicity.