Formation of spindlelike aggregates and flowerlike arrays of polystyrene-b-poly(acrylic acid) micelles

In this letter we describe a simple physical method for the ordered aggregation of scattered single spherical polystyrene-b-poly(acrylic acid) (PS-b-PAA) micelles. First, narrow dispersed spindlelike aggregates, about 60 nm in diameter and 1.5 mum in length, are obtained from the aggregation of single spherical PS-b-PAA micelles at 0 degreesC on a glass slide. Then, the yielding spindlelike units can further aggregate into long-ranged, close-packed, flowerlike arrays after a given amount of freeze-thaw cycles. The formation of the interesting arrays is ascribed to the templated aggregation of micelles on the water polycrystal at the freezing point.