EVA/PBT nanostructured blends synthesized by in situ polymerization of cyclic cBT (cyclic butylene terephthalate) in molten EVA Walid Bahloul a, b, c , Ve ´ronique Bounor-Legare ´ a, b, c, * , Françoise Fenouillot a, b, d , Philippe Cassagnau a, b, c a Universite´ de Lyon, F-69000 Lyon, France b Universite´ Lyon 1, F-69622 Villeurbanne, France c CNRS, UMR5223, Inge´nierie des Mate´riaux Polyme `res, Laboratoire Mate´riaux Polyme`res et Biomate ´riaux, F-69622 Villeurbanne, France d CNRS, UMR5223, Inge´nierie des Mate´riaux Polyme `res, Laboratoire Mate´riaux Macromole´culaires, F-69621 Villeurbanne, France article info Article history: Received 16 October 2008 Received in revised form 3 March 2009 Accepted 27 March 2009 Available online 16 April 2009 Keywords: Copolymers In situ polymerization cBT abstract Poly(ethylene-co-vinyl acetate) (EVA)/poly(butylene terephthalate) copolymers were synthesized by the in situ polymerization of cyclic butylene terephthalate monomer (cBT) in the presence of molten EVA copolymer. Titanium phenoxide Ti(OPh) 4 which leads to the highest degree of grafting compared to the more classical titanium system was used as the initiator for the ring-opening polymerization of the cBT monomer. The corresponding copolymer was characterized fully by 1 H NMR after selective extraction from the blend. As a result, a maximum of 11.3 wt% of EVA-g-PBT copolymer was synthesized by this method. Examination of morphology by transmission electronic microscopy (TEM) showed a fine dispersion of PBT phase with size ranging from 100 to 500 nm in diameter. This gave evidence for a crown structure of the PBT phase that is coated by EVA-g-PBT copolymer. Finally, rheological and mechanical studies highlighted a specific behaviour of this material with improved mechanical properties at room temperature. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Recently, several strategies have been developed to reach well structured polymer blends at the micro and nano-scale as described by Harrats et al. [1]. However, there remain a need for research into the synthesis of block or graft copolymers that would present ideally the ability to give nanostructures; this work is both scientifically challenging and industrially important. Reactive extrusion [2] in particular represents an attractive way to obtain such specific nanostructures. Generally, there are three main ways of synthesis of such copolymers: a) Living copolymerization b) Chemical modification by post polymerization c) Coupling between two appropriately functionalized polymer chains Methods a) and b) are associated with ‘‘the grafting from’’ approach and method c) belongs to the ‘‘grafting onto’’ route. Structures of copolymers obtained through methods b) and c) are specifically relevant to reactive extrusion since they are unattain- able by classical copolymerization method. However, the main difficulty lies in the fact that the polymers/polymers or polymers/ monomers systems are generally not miscible. The chemical reac- tion occurs at the interface and thus a large quantity of copolymer is difficult to obtain. This interfacial reaction leads to compatibiliza- tion of the blends by reactive mixing [3]. Thus, when synthesis of nanostructured copolymers or blends is required, other parameters have to be optimized in order to increase the concentration of the copolymers synthesized. In this case, the copolymers would arrange themselves at a nanometric scale but would also be orga- nized at a larger scale, forming ultimately a fully nanostructured material. The formation of such a nanostructured material has to be related to the architecture of the copolymers based in particular on the size and the molar masses of the sequences or the grafts and also on the grafting ratio (copolymer concentration) and the type of reactive chains (position of the functional reactive group). For example, based on the coupling between two appropriately func- tionalized polymer chains, relevant results were reported by Leibler and his group [4–7]. They succeeded in the self-organization of grafted copolymers of poly (methylmethacrylate)/polyamide 6 and polyolefin/polyamide obtained by reactive mixing in the molten state. On the other hand, Flat [8] reviewed the synthesis by reactive extrusion and the characterization of new materials based on * Corresponding author. Universite ´ de Lyon, F-69000 Lyon, France. Tel.: þ334 72 44 82 12; fax: þ334 78 89 25 83. E-mail address: Veronique.bounor-legare@univ-lyon1.fr (V. Bounor-Legare ´). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2009.03.055 Polymer 50 (2009) 2527–2534