SYNOPSISX-ray photoelectron spectroscopy (XPS) is used to compare the surface behavior in various binary systems of poly (dimethylsiloxane) with poly( bisphenol A sulfone) and poly-(bisphenol A carbonate). All the systems studied show a pronounced surface enrichment in siloxane. At a fixed siloxane concentration in the bulk the lowest extent of surface enrichment is observed in the neat copolymers, next go the blends of copolymers in homopolymers, and the highest extent of surface enrichment is characteristic of the blends of homopolymers. The blends of two copolymers show an unexpected surface behavior: The addition of minor amounts of a siloxane-rich copolymer to another copolymer possessing a much lower siloxane content decreases (rather than increases) the surface siloxane concentration of the latter. A microscopic model is suggested to explain the observed surface behavior. The model involves the formation of a "quasi-two-dimensional" overlayer of additive's macromolecules on the blend surface, with the macromolecules oriented preferentially parallel to the sample surface.

Polyaniline was doped with dodecylbenzenesulfonic acid (Pani ⅐ DBSA) in an agate mortar and used as a conductive additive in melt blends with styrenebutadiene-styrene (SBS) block copolymer. These blends exhibit relatively high levels of electrical conductivity at low-weight fractions of the polyaniline complex. The melt blending process, performed in a two-roll mill or in a Haake internal mixer, increased the protonation degree of the Pani ⅐ DBSA, as indicated by X-ray photoelectron spectroscopy analysis. This result confirms the occurrence of a second doping process at high temperature. The mechanical performance decreases as the amount of Pani ⅐ DBSA in the blend increases, indicating a plasticizing effect of the DBSA. The higher temperature used in blending imparts better conductivity value but gives rise to a strong crosslinked material because of the presence of the sulfonic acid and the high extent of double bonds in the SBS compound.

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X-ray photoelectron spectroscopy (XPS) has been employed to investigate the protonation degree of polyaniline doped with dodecylbenzenesulfonic acid (Pani. DBSA) obtained by different synthetic methods. The protonation degree has been compared to electrical conductivity. Pani.DBSA prepared through the redoping process in an agate mortar displays conductivity values within the range of 1 S/cm. A protonation level of 48% with almost all imine groups being protonated. Pani.DBSA was also synthesized by oxidative polymerization of aniline in the presence of DBSA, which acts simultaneously as a surfactant and as protonating agent. This in situ doping polymerization was carried out in aqueous or toluene media. In both cases, protonation degrees higher than 50% have been achieved, indicating that a substantial portion of amine units have also been protonated. Higher doping degree has been achieved by aqueous dispersion polymerization of aniline. The C/N and S/N molar ratios obtained by XPS analysis indicate that the polyaniline chains obtained by in situ polymerization are protonated by both sulfonate and hydrogen sulfate anions.

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