SURFACE SEGREGATION IN BLENDS OF POLYSTYRENE AND PERFLUOROHEXANE DOUBLE END-CAPPED POLYSTYRENE STUDIED BY STATIC SIMS, ISS, AND XPS

The surface composition of styrene polymers capped at one or both ends by perfluoro groups has been determined by ISS, XPS, and static SIMS. The homopolymers, with M(n) 29000-59000, have an excess of the perflu oro end groups at the surface that is inversely proportional to the ch ain length and is commensurate with one or both ends having perfluoro groups. In contrast, double perfluoro end capped homopolymers of M(n) similar to 9000 have only one of the perfluoro groups at the surface. In blends of perfluoro end capped styrene with hydrogen-terminated sty rene, the fluorinated end cap causes the former to segregate to the su rface. Nevertheless, the extents of segment segregation of single and double perfluoro end capped polymers of weights 29000-59000 are simila r. For blends of perfluoro-capped polymer with M(n) 9000 in styrene of M(n) 30000, the molecular weight and perfluoro end caps both strongly influence the segment segregation. The concentration of fluorine at t he surface of all the blends may be estimated from the homopolymer XPS data and the blend monomer composition determined by static SIMS.