Well-Defined Star-Shaped Aromatic Polyamides from Chain-Growth Polymerization of Phenyl 4-(Alkylamino)benzoate with Multifunctional Initiators

For the synthesis of well-defined star-shaped aromatic polyamides, triphenyl benzene-1,3,5-tricarboxylate ( 2a ), tetraphenyl benzene-1,2,4,5-tetracarboxylate ( 2b ), and 1,3,5-tris(4-phenyloxycarbonylbenzyloxy)benzene ( 3 ) were synthesized and then employed as multifunctional initiators for the chain-growth polymerization of phenyl 4-(octylamino)benzoate ( 1 ). The polymerization with 2a or 2b did not proceed smoothly from all of the phenyl ester moieties in the initiators and afforded polymers with high polydispersities. In contrast, initiator 3 having the benzyloxy spacers resulted in three-armed aromatic polyamide ( I ) with low polydispersity. Furthermore, the benzyloxy linkages of the core of I were cleaved by hydrogenolysis to yield a polymer with low polydispersity, the M n of which was one-third that of I, indicating that I exactly possesses three arm chains of a uniform and controlled length. However, the polymerization at higher feed ratios of [ 1 ] 0 /[ 3 ] 0 afforded not only the three-armed polymer but also a linear polymer formed by self-polymerization of 1 .