Solid-state NMR study of biodegradable starch/polycaprolactone blends Jir ˇı ´ Spe ˇva ´c ˇek a, * , Jir ˇı ´ Brus a , Thomas Divers b , Yves Grohens b a Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic b Laboratoire Polyme `res, Proprie ´te ´s aux Interfaces et Composites, Universite ´ de Bretagne-Sud, Rue de Saint Maude ´, BP 92 116, 56321 Lorient, France Received 19 December 2006; received in revised form 9 February 2007; accepted 14 February 2007 Available online 25 February 2007 Abstract Abundant literature exists on starch or modified starch blended with biodegradable polyesters to achieve good perfor- mance with cheap compost plastics. The level of miscibility in these blends is one of the most relevant parameters. In the present study, solid-state 1 H and 13 C NMR spectra, as well as carbon spin-lattice relaxation times T 1 (C) and proton spin- lattice relaxation times T 1 (H) and proton spin-lattice relaxation times in the rotating frame T 1q (H) of biodegradable starch (or starch formate)/polycaprolactone (PCL) (or polyester (PE) oligomers) blends and samples of the neat components were measured. From the T 1q (H) and T 1 (H) relaxation times it follows that blends starch/PCL, starch/PE-oligomers and starch formate/PE-oligomers are phase separated even on the scale of 20–110 nm. On the contrary starch formate/PCL blend is phase separated on the scale 2.5–12 nm but homogeneously mixed on the scale 20–90 nm. Moreover, shorter T 1 (C) and especially T 1q (H) values found for the starch or starch formate component in all these blends in comparison with neat sam- ples show that molecular mobility of starch and starch formate segments is affected by blending. This indicates some mis- cibility also in phase separated blends which can happen in amorphous channels of starch. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Biodegradable blends; Molecular morphology; Starch; Starch formate; Polycaprolactone; Solid state NMR 1. Introduction Research on biodegradable polymers has received increasing attention in recent years because of their wide applications in environmental friendly packag- ing, biomedical materials, but also in various indus- trial applications such as computer and mobile phone industry. The most popular and biodegrad- able polymers are aliphatic polyesters, such as polyc- aprolactone (PCL), polylactic acid, poly(butylene adipate terephthalate) and polyhydroxybutyrate. However, since these polymers are still expensive and do not match all the technical requirements for possible applications, blends of these polymers with starch, which is a cheap abundant resource, lead to large number of papers and patents [1–10]. Impor- tant requirements for packaging materials, such as films, are high flexibility, medium Young’s modulus at room temperature and blow or cast processing ability. Barrier properties are also relevant for these 0014-3057/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2007.02.021 * Corresponding author. Tel.: +420 296809380; fax: +420 296809410. E-mail address: spevacek@imc.cas.cz (J. Spe ˇva ´c ˇek). European Polymer Journal 43 (2007) 1866–1875 www.elsevier.com/locate/europolj EUROPEAN POLYMER JOURNAL