Dendrimer-like Star Polymers

Dendrimer-like star polymers, a novel type of molecular architecture, have been synthesized. The architecture of the new polymers resembles that of three-dimensional spherical dendrimers as well as classical star polymers. The controlled structures, based on aliphatic polyesters, are synthesized by a divergent growth approach. A hexa hydroxy-functional 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) derivative was used as the “initiator” for the stannous-2-ethylhexanoate (Sn(Oct)2) catalyzed living ring opening polymerization of e-caprolactone. The polymerization generated a six-arm polymer with a molecular weight of 14 300 (Mn) and a Mw/Mn of 1.06. The new polymer was functionalized with a protected bis-MPA, deprotected, and used as the “macroinitiator” for the polymerization of a second generation 12 armed poly(e-caprolactone) (Mn = 42 300, Mw/Mn = 1.16). Another iteration of the same procedure generated a third generation 24 arm dendrimer-like star polymer with a Mn of 96 000 and Mw/Mn of 1.14. The comp...