Macromolecular Nanotechnology Synthesis of waterborne acrylic/clay nanocomposites by controlled surface initiation from macroinitiator modified montmorillonite Matej Mic ˇušík 1 , Audrey Bonnefond, Maria Paulis ⇑ , Jose R. Leiza Institute for Polymer Materials, POLYMAT and Grupo de Ingeniería Química, Dpto. de Química Aplicada, University of the Basque Country (UPV/EHU), Joxe Mari Korta Zentroa, Tolosa Etorbidea 72, 20018 Donostia-San Sebastián, Spain article info Article history: Received 21 July 2011 Received in revised form 7 February 2012 Accepted 4 March 2012 Available online 11 March 2012 Keywords: Polymer/clay nanocomposites Living/controlled polymerization Miniemulsion polymerization Adhesive properties abstract The nitroxide mediated controlled surface initiated polymerization of methyl methacrylate (MMA)/butyl acrylate (n-BA) was carried out with a macroinitiator modified montmoril- lonite. The macroinitiator was synthesized by the nitroxide mediated polymerization of vinylbenzyl trimethylammonium chloride (VBTMACl), methylmethacrylate (MMA) and styrene (S) at 90 °C using BlocBuilder Ò . The macroinitiator was exchanged with the sodium cations of the montmorillonite, to yield surface modified reactive montmorillonite. The bulk polymerizations of BA/MMA from the clay surface produced controlled molecular weight polymers that were able to exfoliate the clay. This controlled polymer/clay nano- composite was used as masterbatch and further dispersed in monomers and miniemulsi- fied to perform miniemulsion polymerization of BA/MMA (90/10 wt.%) at 30 wt.% solids content at low emulsifier concentration. The adhesive properties of the nanocomposites prepared with the masterbatch were proved to be better than those prepared with an organically modified clay. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The enhanced thermal, barrier, mechanical and flamma- bility properties of polymer/clay nanocomposites (PCN) have attracted the interest of many industrial and academic researchers in the last two decades [1–5]. This enhancement comes from the enormous interfacial area created by the high aspect ratio of the clay platelets (around 100 nm wide and 1 nm thick, depending on the clay type) upon complete exfoliation of the clay in the polymer matrix. If in addition to the exfoliation of the platelets, they are fully compatible with the polymer matrix, the properties of the hybrid materials exceed most of the expected application proper- ties. Clays are naturally hydrophilic, and their compatibility with organic polymers is not straightforward. In fact an or- ganic modification of the clay with a quaternary ammonium organic salt is usually performed before its incorporation to the polymer in the three most used addition methods: melt intercalation, intercalation from solution or in situ intercalative polymerization. However, this simple cationic exchange does not always assure the complete compatibility between the clay and the polymer, and a more favorable compatibility is often pursued by the attachment of the polymer itself to the clay. Two methods have been reported to accomplish this work: the grafting to and the grafting from methods. In the grafting to method, the organic salt to be exchanged in the clay interlayer bears a double bond able to polymerize and to be incorporated in the polymer backbone [6–9]. In the grafting from or surface initiated method, an initiator is ini- tially attached to the clay and the polymerization is ex- pected to occur by the addition of monomer units to the attached initiator fragment. Either azo [10–13] or peroxi [14,15] type initiators have been used. However in most of the cases the efficiency of the initiator was low, and only 0014-3057/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2012.03.002 ⇑ Corresponding author. E-mail addresses: maria.paulis@ehu.es (M. Paulis), jrleiza@ehu.es (J.R. Leiza). 1 On leave from Slovak Academy of Sciences, Polymer Institute, Depart- ment of Composite Materials, Dubravska cesta 9, 845 41 Bratislava, Slovakia. European Polymer Journal 48 (2012) 896–905 Contents lists available at SciVerse ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj MACROMOLECULAR NANOTECHNOLOGY