Facile synthesis of eight-membered cyclic(ester-amide)s and their organocatalytic ring-opening polymerizations

Five eight-membered cyclic(ester-amide)s (M1-M5) were synthesized from phthalic anhydride and beta-amino alcohols by sequential nucleophilic addition and intramolecular esterification. The organocatalytic ring-opening polymerization (ROP) of these monomers with 1,5,7-triazabicyclo[4.4.0]-dec-5-ene (TBD) and 1,8-diazabicyclo[5.4.0]undecane-7-ene (DBU)/thiourea (TU) as the catalysts was investigated, and they could all be polymerized in a controlled manner under optimized conditions, affording well-defined poly(ester-amide)s (PEAs) (P1-P5) with tailored molar masses and narrow dispersities. The structures of these PEAs were characterized, confirming that the main-chain tertiary amide bonds existed as a mixture of cis/trans isomers. These PEAs are amorphous materials with high thermal stability (T-d,T-5%: 260-301 degrees C) and side chain-dependent glass transition temperatures (T(g)s) (62-138 degrees C). Polymer P1 contains both a rigid benzene ring and a pyrrole ring in the backbone, being a PEA with the highest T-d,T-5% (301 degrees C) and T-g (138 degrees C). The TBD-catalyzed copolymerization of M1 and rac-LA could generate a series of random copolymers with tunable and enhanced T(g)s (52-96 degrees C) with increasing incorporation ratio of M1 (0-51 mol%). Finally, These PEAs could be selectively and completely converted into their corresponding monomer precursors in alkaline aqueous solutions.