A novel hyperbranched copolymer (HBCP), with a numberaverage molecular weight from 11000 to 25000, was successfully prepared by the direct condensation polymerization of a unimolecular 3-armed 4-N-methylbenzamide pentamer (TMA-3MAB 5 ) as a hard segment (B 3 monomer), with aminefunctionalized poly(propylene oxide) (PPO x ) (x: degree of polymerization, 32 or 64) (A 2 monomer) at both ends as a soft segment, and investigated its possibility as a thermoplastic elastomer. The highly pure B 3 molecule, TMA-3MAB 5 , was quantitatively obtained by the step-growth reaction of 4-(Nmethylamino)benzoic acid (MAB) using thionyl chloride as the condensation reagent and trimesic acid (TMA) as the core molecule in N-methylpyrrolidone (NMP) at 20°C for 0.5 h for each step. The HBCP showed two glass transitions corresponding to imperfectly segregated PPO-rich and polybenzamide hard segment-rich domains, and the film showed good mechanical properties (Young's Modulus T M 0.254.0 MPa, elongation at break E B 1331470%), which were controlled by the fraction of the hard segment.A variety of tailor-made architectures, such as well-defined diblock, star-shaped, comb-shaped, and hyperbranched copolymers, and dendrimers have been attained through recent rapid advances in macromolecular engineering.1 Such architectures have contributed to the discovery of a number of higher ordered structures, and thus the range of the application of polymeric materials has exponentially been widened. 2 We have prepared a series of poly(N-alkylbenzamide)s (PABA n : n indicates the number of carbon atoms of the alkyl substituent) by the direct condensation polymerization of 4-(N-alkylamino)benzoic acids, and the structures and the packing of the PABA n polymers have been elucidated using IR spectroscopy, elemental analysis, DSC, WAXD, and SAXS, which show that PABA n (n = 15) molecules are rigid, and thus possess a crystalline structure, such as in monoclinic and orthorhombic packing lattices, depending on the length of the alkyl substituents.3
