Alternating poly(ester amide)s from succinic anhydride and α,ω‐amino alcohols: synthesis and thermal characterization

Alternating poly(ester amide)s 6a – e from succinic anhydride and α,ω‐amino alcohols H 2 N—(CH 2 ) x —OH ( x = 2–6) 2a–e were obtained in two steps: α‐carboxyl‐ω‐hydroxy amides 3a–e were prepared from the starting materials in a highly selective reaction, followed by a polycondensation reaction. 1 H and 13 C NMR analyses of the poly(ester amide)s clearly reveal the alternating microstructure. The poly(ester amide)s with homologous α,ω‐amino alcohols H 2 N—(CH 2 ) x —OH ( x = 2–6) are semi‐crystalline materials, their melting points show the odd/even effect observed for [n]‐polyamides and [n]‐polyurethanes. Heating the poly(ester amide)s 6a–e yields the corresponding N ‐(hydroxyalkyl) imides 4a–e with no trace of cyclic ester amides. Theoretical calculations revealed that the cyclic ester amides 5a–e are clearly richer in energy than the isomeric N ‐(hydroxyalkyl) imides. These results show that cyclic ester amides can not be prepared from N ‐(hydroxyalkyl) imides by ring‐enlargement reactions. Copyright © 2003 Society of Chemical Industry