Synthesis of Poly(ester amide)s Derived from Glycolic Acid and the Amino Acids: b-Alanine or 4-Aminobutyric Acid Alfonso Rodrı ´guez-Gala ´n, Montserrat Vera, Katia Jime ´nez, Lourdes Franco, Jordi Puiggalı ´* Departament d’Enginyeria Quimica, ETS d’Enginyeria Industrial, Universitat Polite `cnica de Catalunya, Diagonal 647, Barcelona E-08028, Spain Fax: 0034 93 4017150; E-mail: Jordi.Puiggali@upc.es Received: May 8, 2003; Accepted: August 26, 2003; DOI: 10.1002/macp.200350064 Keywords: differential scanning calorimetry (DSC); glycolic acid; NMR; poly(ester amide)s; solid-state polymerization Introduction Polymers based on glycolic acid are nowadays the fibers most used as surgical sutures. [1] The high glass transition temperature of poly(glycolic acid) forces its processing as a multifilament (SAFIL 1 , DEXON 1 ) to reduce rigidity, but at the same time, a coating is usually needed to solve problems associated with capillarity or to the drag tissue. Flexibility may also be improved by copolymerization with other monomers, such as lactic acid (VICRYL 1 , POLY- SORB 1 ), e-caprolactone (MONOCRYL 1 ), trimethylcar- bonate (MAXON 1 ), or a mixture of monomers, like e-caprolactone and trimethylcarbonate (MONOSYN 1 ) or p-dioxanone, and trimethylcarbonate (BIOSYN 1 ). Thus, it is possible, in some cases, to commercialize the suture as a non-coated monofilament. Furthermore, the composition changes allow for a wide range of materials for applications with different suture absorption times. Recent efforts have been focused on the incorporation of natural a-amino acids, [2–4] since they may enhance the susceptibility towards enzymatic degradation, putatively improve their intermolecular interactions due to the Full Paper: The polymerization of metal salts of N- chloroacetyl-b-alanine and N-chloroacetyl-4-aminobutyric acid was investigated. The former gives a mixture of polymer and a seven-membered cyclic compound constituted of glycolic and b-alanine units, and its reaction proceeds in the solid state. However, liquefaction is observed in the second case giving rise to a polymer with a moderate molecular weight. Condensation kinetics of both sodium and silver salts of N-chloroacetyl-b-alanine have been studied by differential scanning calorimetry. Copolymers of glycolic acid and b-alanine with a molar ratio of glycolic acid/b-alanine varying from 0.5 to 1.0 have been synthesized by thermal reaction of co-precipitated crystals of the sodium salts of chloroacetic acid and N-chloroacetyl-b-alanine. NMR spec- troscopy indicates that copolymers tend to have a random distribution. The resulting new poly(ester amide)s have been characterized by spectroscopy and thermal analysis. DSC heating runs corresponding to different mixtures of the sodium salts of chloroacetic acid and chloroacetyl-b-alanine. 2078 Macromol. Chem. Phys. 2003, 204, 2078–2089 Macromol. Chem. Phys. 2003, 204, No. 17 DOI: 10.1002/macp.200350064 ß 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim