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 (1) 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 1, 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.