Polycondensation of phenyl 4‐(octylamino)benzoate (1) in the presence of diphenyl terephthalate (2) as a difunctional initiator proceeded in a bidirectional propagation from 2. This polycondensation was applied to the synthesis of poly(ethylene glycol) (PEG)–aromatic polyamide–PEG triblock copolymer (4) as a new, well‐defined coil‐rod‐coil triblock copolymer.
For the synthesis of well-defined star-shaped aromatic polyamides, triphenyl benzene-1,3,5tricarboxylate (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 chaingrowth 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.
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