POLYSTYRENE-DENDRIMER AMPHIPHILIC BLOCK-COPOLYMERS WITH A GENERATION-DEPENDENT AGGREGATION

A class of amphiphilic macromolecules has been synthesized by combinin g well-defined polystyrene (PS) with poly(propylene imine) dendrimers. Five different generations, from PS-dendr-NH2 up to PS-dendr-(NH2)(32 ), were prepared in yields of 70 to 90 percent. Dynamic light scatteri ng, conductivity measurements, and transmission electron microscopy sh ow that in aqueous phases, PS-dendr-(NH2)(32) forms spherical micelles , PS-dendr-(NH2)(16) forms micellar rods, and PS-dendr-(NH2)(8) forms vesicular structures. The lower generations of this class of macromole cules show inverted micellar behavior. The observed effect of amphiphi le geometry on aggregation behavior is in qualitative agreement with t he theory of Israelachvili et al. The amphiphiles presented here are s imilar in shape but different in size as compared with traditional sur factants, whereas they are similar in size but different in shape as c ompared with traditional block copolymers.