SURFACE-COMPOSITION OF POLY(METHYLPHENYLSILOXANE)-POLYSTYRENE BLOCK-COPOLYMERS

The surface compositions of poly(methylphenylsiloxane) (PMPS) homopoly mers and poly(methylphenylsiloxane) - polystyrene (PMPS-PS) diblock co polymers have been analyzed using time-of-flight secondary ion mass sp ectrometry (TOFSIMS). The high surface sensitivity of this method, whi ch probes samples to depths of a few Angstroms, showed the block copol ymer samples to have both poly(methylphenylsiloxane) and polystyrene s egments present at the surface. These results may be contrasted with t he behavior seen for poly(dimethylsiloxane) (PDMS) blocks and blends, where the low surface energy of the -[O-Si(CH3)(2)]- repeat units typi cally leads to surface segregation and complete PDMS surface coverage is seen. Investigation of the thermal characteristics of the block cop olymers by differential scanning calorimetry revealed a single glass t ransition temperature, indicating a single phase morphology. The surfa ces of the block copolymers also showed an enrichment of -Si(CH3)(3) g roups, which are the terminal groups of the PMPS, presumably due to th e low surface energy of the trimethylsilyl groups.