INTERFACIAL BEHAVIOR OF BLOCK POLYELECTROLYTES .5. EFFECT OF VARYING BLOCK LENGTHS ON THE PROPERTIES OF SURFACE MICELLES

Block polyelectrolytes P(S(m)-b-VP(n)/C10I) composed of polystyrene blocks (m = 54-480) and perdecylated poly(4-vinylpyridine) (n = 3-240) have been studied using the Langmuir film balance technique and the corresponding Langmuir-Blodgett films. The recently reported phenomenon of surface micelle formation1 has been found to be very general for those types of materials. Different morphologies, as visualized by transmission electron microscopy, arise, depending on the diblock composition. An unusual phase transition originates from one of the morphological units, i.e., small, circular starfish micelles, and is consistent with an ionic chain solubilization process induced by film compression. As the relative ionic block length is decreased, other morphologies are observed. The properties of surface rod aggregates are consistent with the rods being made up of two layers of the diblocks, with the PS blocks forming the core. Large planar aggregates also form, and appear to be one PS block thick and can extend up to several microns in width. Compressional hysteresis, temperature effects, and aggregation numbers have been used to provide a self-consistent description of the surface micellization phenomenon.