Synthesis of hyperbranched aromatic polyamides starting from dendrons as ABx monomers:: Effect of monomer multiplicity on the degree of branching

Three hyperbranched aromatic polyamides were synthesized by the direct polycondensation of 3,5-diaminobenzoic acid 2 (AB(2) monomer), G1 dendron 4 (AB(4) monomer), and G2 dendron 6 (AB(8) monomer). The weight-average molecular weights (M-w) of the resulting polymers were 100 000-200 000 with a polydispersity (PDI) of ca. 3. The degrees of branching (DB) of the polymers from 2, 4, and 6 were 0.32, 0.72, and 0.84, respectively, as determined by H-1 NMR spectroscopy. Thermal polymerization of 2 and 4 was also carried out to form hyperbranched polyamides without solvents and catalysts. The resulting polymers by the thermal polymerization had M-w's of around 20 000 with a PDI of around 2. DB of the hyperbranched polymers could be controlled within a range of 0.32-0.72 by the copolymerization of 2 and 4 in different molar ratios. DB had little influence on the T-g and solubility of the polymers.