SURFACE SEGREGATION STUDIES OF FLUORINE-CONTAINING DIBLOCK COPOLYMERS

A diblock copolymer of deuterated styrene and isoprene (dPS-PI) with a small volume fraction of isoprene was chemically modified to incorpor ate pendant fluorinated side chains (''fingers''). The composition dis tribution of the diblock copolymers within a high molecular weight pol ystyrene (PS) homopolymer was determined by forward recoil spectrometr y. Surface segregation and interfacial segregation of the modified blo ck copolymers from a polystyrene matrix are observed in as-spun films. Equilibrium segregation was achieved on annealing at 160 degrees C fo r several days. The segregation isotherms at the air-polymer interface are shown to be quantitatively described by a self-consistent mean fi eld theory (SCMF), and these permit us to estimate an effective Flory parameter which describes the attraction of the fluorinated segments t o the surface and their repulsion from the bulk. The change in the sur face tension as a result of the adsorption of the block copolymers at the air-homopolymer interface was evaluated from the predictions of SC MF theory and compared with the changes in the water contact angle obs erved. Advancing water contact angle data are consistent with the pres ence of a nonuniform layer of PS, CF2, and CF3 segments on the surface of the segregated samples.