Synthesis of novel hyperbranched poly(ester-amide)s based on acidic and basic amino acids via "AD plus CBB '" couple-monomer approach

A series of novel hydroxyl- or methyl ester- terminated hyperbranched poly(ester-amide)s (HBPEAs) based on acidic (L-glumatic acid and L-aspartic acid) and basic amino acids (L-lysine) have been synthesized via the "AD + CBB'" couple-monomer approach. The ABB' intermediates were stoichiometrically formed through thio-ene reaction benefited from reactivity differences between functional groups. Without any purification, in situ self-polycondensations of the intermediates at elevated temperature in the presence of Ti(OBu)(4), as a catalyst, afforded HBPEAs with high molecular weights. More rapid polymerization rate and much higher molecular weight as well as broader polydispersity were observed for the polymerization process of intermediates based on acidic amino acids than basic amino acids which is related to the catalytic mechanism and structure difference of intermediates. Moreover, polymerization of intermediate derived from L-aspartic acid was carried out faster by comparison with that from L-glumatic acid. The DB values were approximately estimated to be 47%-49% for the polymers derived from L-aspartic acid and L-glutamic acid. The resultant HBPEAs possessed glass transition temperature (T-g) in the range of 3 to 11 degrees C, among which those derived from L-lysine shows the highest Tg, and decomposition temperatures at 10% weight loss under air and nitrogen are in close regions of 261-271 degrees C and 264-268 degrees C, respectively. (C) 2011 Elsevier Ltd. All rights reserved