Enhanced Surface Properties of Branched Poly(ether sulfone) from Semifluorinated Polyhedral Oligomeric Silsequioxanes

Hybrid systems in which poly(ether sulfone) (PESU) chains are grafted to semifluorinated polyhedral oligomeric silsesquioxane (POSS) cores are expected to integrate the advantages of both fluoropolymers and POSS into the polymer system to yield excellent surface properties. For that purpose, we synthesized a novel octa-functional perfluorocyclopentenyl-POSS (PFCP-POSS), which was used as a "core" grafting point. Commercial PESU was successfully grafted to PFCP-POSS via the nucleophilic addition-elimination reaction between the phenolic chain ends and reactive PFCP moieties to yield a hybrid branched polymer possessing a semifluorinated POSS core. X-ray photoelectron spectroscopy, neutron reflectivity, and atomic force microscopy indicated that the preparation of nanostructured polymer surfaces occurs by migration of the low surface energy components (PFCP-POSS molecules), while POSS aggregation is suppressed by covalent attachment to the long PESU chains. The resulting PFCP-POSS modified PESU films were highly transparent and yielded hydrophobic surfaces with low surface energy and high modulus for potential applications in high performance coatings and composites.