A class of amphiphilic macromolecules has been synthesized by combining well-defined polystyrene (PS) with poly(propylene imine) dendrimers. Five different generations, from PS- dendr -NH 2 up to PS- dendr -(NH 2 ) 32 , were prepared in yields of 70 to 90 percent. Dynamic light scattering, conductivity measurements, and transmission electron microscopy show that in aqueous phases, PS- dendr -(NH 2 ) 32 forms spherical micelles, PS- dendr -(NH 2 ) 16 forms micellar rods, and PS- dendr -(NH 2 ) 8 forms vesicular structures. The lower generations of this class of macromolecules show inverted micellar behavior. The observed effect of amphiphile geometry on aggregation behavior is in qualitative agreement with the theory of Israelachvili et al . The amphiphiles presented here are similar in shape but different in size as compared with traditional surfactants, whereas they are similar in size but different in shape as compared with traditional block copolymers.
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A new class of amphiphilic macromolecules has successfully been synthesized by creating well-defined di block copolymers of polystyrene (PS. M n = 3.2 x 10\ M J M n = 1.04) with poly propylene imine) dendrimers. A poly styrene core molecule with a primary amine end-group was prepared by a quan titative three-step modification procedure of acid-functionalized polystyrene. On this core molecule, five different genera tions from PS-dendr-'NH2 up to PS-dendr-(N H 2 ) 32 were constructed in high yields.The molecular structure of the block co polymers was analyzed in detail with NM R and IR spectroscopy and electro spray mass spectrometry. With conduc tivity measurements and monolayer pres sure-area isotherm determinations, we observed generation-dependent am phiphilic behavior. Dynamic light scatterKeywords amphiphiles • block copolymers • dendrimers • micelles • surfactants ing and transmission electron microscopy showed that amphiphile geometry had a distinct effect on aggregation behavior; W C r C rthis is in qualitative agreement with Israelachvili's theory. Critical associa tion concentrations determined with the pyrene probe luminescence technique were as low as 5 x 1 0 _ 7 m. The am phiphiles presented here, therefore, show a resemblance to traditional block copoly mers with regard to size and stability, and are similar to surfactants with respect to tuning of the shape.
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