Crystallization Studies on a Clay Nanocomposite Prepared From a Degradable Poly(ester amide) Constituted by Glycolic Acid and 6-Aminohexanoic Acid Laura Morales-Ga ´ mez, 1,2 Lourdes Franco, 1,2 Marı ´a Teresa Casas, 1 Jordi Puiggalı´ 1,2 1 Departament d’Enginyeria Quı´mica, Universitat Polite ` cnica de Catalunya, E-08028 Barcelona, Spain 2 Centre de Recerca en NanoEnginyeria (CRNE), Universitat Polite ` cnica de Catalunya, E-08028 Barcelona, Spain An intercalated nanocomposite was prepared from an organomodified clay (Cloisite 25A) and a new biode- gradable poly(ester amide) characterized by an alter- nating arrangement of glycolic acid and 6-aminohexa- noic acid units by the melt-mixing technique. The influ- ence of the final silicate layer morphology on hot and cold crystallization behavior was investigated by opti- cal microscopy, differential scanning calorimetry, and synchrotron radiation. Primary nucleation increased significantly with the incorporation of nanoparticles, in contrast with the decrease previously observed when exfoliated structures were obtained. The secondary nucleation constant was higher for the nanocomposite sample, indicating that the growth mechanism was hampered by the presence of clay particles. However, the increase in primary nucleation had a greater effect, resulting in a faster overall crystallization rate for the nanocomposite. The addition of clay particles slightly reduced the degree of crystallinity attained after the hot and cold crystallization processes and favored a lamellar insertion mechanism. POLYM. ENG. SCI., 51:1650–1661, 2011. ª 2011 Society of Plastics Engineers INTRODUCTION The development of biodegradable polymers is one of the most interesting topics because these materials have potential applications as commodities and specialities, mainly in the biomedical field. In this sense, biodegrad- able polymers are regarded as a potential alternative to existing petroleum-based polymers because trends focus on promoting the use of environmentally friendly materi- als despite their higher production costs [1, 2]. Aliphatic polyesters are the most commonly used family of poly- mers because of the presence of hydrolyzable ester groups. However, mechanical and thermal properties are often not sufficient to meet the requirements of commod- ity applications. Several alternatives have, therefore, been considered to improve performance properties, like the incorporation of amide groups in the main chain, which allows establishing strong hydrogen bonding intermolecu- lar interactions. Thus, interest is increasing in poly(ester amide)s [3–11] to the point that this new family of biode- gradable polymers is even being considered for commer- cialization (e.g., BAK TM , a poly(ester amide) derived from 1,4-butanediol, adipic acid, and 6-aminohexanoic acid [12]). The properties of polymers can also be significantly modified by adding layered silicates, as demonstrated by pioneering works performed with nylon 6-clay nanocom- posites [13, 14]. Since then, the preparation of nanocom- posites based on biodegradable polymer matrices has been extensively studied [15–17] despite potential problems associated with low production level and high costs. We developed a promising synthesis procedure based on a thermal polycondensation that allows obtaining new poly(ester amide)s constituted by an alternating arrange- ment of glycolic acid and x-amino acid units (Fig. 1) [18, 19]. The derivative of 6-aminohexanoic acid [here- after named poly(glc-alt-amh)] was mainly studied because its related homopolymers (i.e., polyglycolide and nylon 6) are samples with well-known applications as bio- degradable and commodity materials, respectively. This polymer was found to be biocompatible [20] and to crys- tallize according to a peculiar structure, which exhibits Correspondence to: J. Puiggalı ´; e-mail: jordi.puiggali@upc.es Contract grant sponsor: FEDER; contract grant number: MAT2009-11503; contract grant sponsor: AGAUR; contract grant number: 2009SGR 1208; contract grant sponsor: CICYT. DOI 10.1002/pen.21936 Published online in Wiley Online Library (wileyonlinelibrary.com). V V C 2011 Society of Plastics Engineers POLYMER ENGINEERING AND SCIENCE—-2011