Dendronized aliphatic polymers by a combination of ATRP and divergent growth

Dendronized, hybrid dendritic-linear polymers were synthesized by either the graft-onto route or by atom transfer radical polymerization (ATRP) of macromonomers. In both ways, the main chain was composed of acrylate repeating units and the dendrons were based on the aliphatic ester skeleton obtained from 2,2-bis(methylol)propionic acid (bis-MPA). ATRP of macromonomers was not a viable route for monomers with side chains larger than second-generation dendrons, which is why a combination of the two approaches was required to obtain polymers with larger side chains. The graft-onto route was conducted by reacting hydroxyl groups on the main chain with the acetonide-protected 2,2-bis(hydroxymethyl)propionic anhydride. The acetonide protecting group was easily removed by treating a solution of the polymer with an acidic ion-exchange resin. Dendronized polymers with 1-3 generation dendron side groups were synthesized with a maximum molecular weight of ca. 86 kDa. The products were analyzed by H-1 and C-13 NMR, SEC, and MALDI-TOF.