Please cite this article in press as: V.S. Nguyen, et al., Inﬂuence of cluster size and surface functionalization of ZnO nanoparti- cles on the morphology, thermomechanical and piezoelectric properties of P(VDF-TrFE) nanocomposite ﬁlms, Appl. Surf. Sci. (2013), http://dx.doi.org/10.1016/j.apsusc.2013.04.070 ARTICLE IN PRESS G Model APSUSC-25539; No. of Pages 8 Applied Surface Science xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Applied Surface Science j ourna l ho me page: www.elsevier.com/locate/apsusc Inﬂuence of cluster size and surface functionalization of ZnO nanoparticles on the morphology, thermomechanical and piezoelectric properties of P(VDF-TrFE) nanocomposite ﬁlms Van Son Nguyen a , Didier Rouxel a,∗ , Brice Vincent a , Laurent Badie c , Fabrice Domingues Dos Santos b , Emmanuel Lamouroux c , Yves Fort c a Institut Jean Lamour, UMR CNRS 7198, Faculté des Sciences et Techniques, Université de Lorraine, 54506 Vandœuvre-lès-Nancy, France b Piezotech S.A.S., 9 rue de Colmar, 68220 Hésingue, France c Structure et Réactivité des Systèmes Moléculaires Complexes, UMR CNRS 7565, Faculté des Sciences et Techniques, Université de Lorraine, 54506 Vandœuvre-lès-Nancy, France a r t i c l e i n f o Article history: Received 29 November 2012 Received in revised form 1 March 2013 Accepted 11 April 2013 Available online xxx Keywords: P(VDF-TrFE) Zinc oxide nanoparticles Nanocomposite Piezoelectric properties Thermomechanical properties a b s t r a c t Few studies have been reported concerning the nanocomposites of copolymers of vinylidene diﬂuoride and triﬂuoroethylene (P(VDF-TrFE)) with piezoelectric nanoﬁllers. This study deals with the prepara- tion and characterization of piezoelectric nanocomposite ﬁlms based on P(VDF-TrFE) ﬁlled with several ZnO piezoelectric nanoparticles with different sizes and surface states. The inﬂuence of cluster size and surface state of ZnO nanoparticles on the morphology and electromechanical properties of (PVDF-TrFE) nanocomposite ﬁlms is investigated. The dispersion of nanoparticles and the microstructure of nanocomposite are observed by Environmen- tal Scanning Electron Microscope (ESEM) and Transmission Electron Microscopy (TEM). The crystallinity of the copolymer matrix is characterized by X-ray diffraction and Differential Scanning Calorimetry (DSC). The piezoelectric and mechanical properties are measured to evaluate the inﬂuence of cluster size and surface functionalization with respect to the P(VDF-TrFE) matrix. The nanocomposites ﬁlled with 10% nanoparticles showed an increase up to 25% of storage modulus while keeping a high piezoelectric activ- ity. Furthermore, storage modulus of nanocomposites slightly linearly increased with decreasing cluster size of nanoparticles. © 2013 Published by Elsevier B.V. 1. Introduction Piezoelectric materials have been widely adopted for many applications such as electromechanical transducers, actuator, and sensors. The most common piezoelectric materials are ceram- ics, i.e. lead zirconate-titanate (PZT), barium titanate (BaTiO 3 ) and lithium niobate (LiNbO 3 ) thanks to their high piezoelec- tric and dielectric properties; however these ceramics are brittle, especially in their bulk form. Recently, piezoelectric polymers, mainly poly(vinylidene diﬂuoride) (PVDF) and its copolymers such as vinylidene diﬂuoride and triﬂuoroethylene (P(VDF-TrFE)) [1–3], have attracted intense scientiﬁc and technological interest. This is mostly due to their unique features, such as ﬂexi- bility, ease of processing, and lightness in spite of their low piezoelectric coefﬁcients compared to ceramic-based materials. Therefore, the combination of the advantages of piezoceramic ∗ Corresponding author. Tel.: +33 03 83 68 46 47; fax: +33 03 83 68 49 33. E-mail addresses: didier.rouxel@univ-lorraine.fr, didier.rouxel@ijl.nancy-universite.fr (D. Rouxel). and piezoelectric polymers has received considerable attention of researchers [4,5], for example the ﬂexible bifunctional composites of P(VDF-TrFE)/lead titanate displaying selectively piezoelectricity or pyroelectricity [6]. Compared to PVDF homopolymer, P(VDF- TrFE) has higher piezoelectric properties, without mechanical stretching. Therefore the copolymers are preferred in the appli- cations of ferroelectric thin ﬁlms on substrates. The nucleation of the ferroelectric phase by several nanoﬁllers has been reported for PVDF [7–9], however the preparation of PVDF solutions often uses toxic solvents such as dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). The strong dependence of the microstructure and properties of P(VDF-TrFE) on the processing conditions [10], thermal annealing [11] and ﬁlm thickness [12] are also observed. Several P(VDF-TrFE)-based composites [10,13–15] and nanocom- posites [16–22] are reported in the literature. However very little data concerning the effect of nanoﬁllers on the morphology and properties of the copolymer is available in the literature [23]. Zinc oxide (ZnO) is one of the most promising materials for optoelectronic, spintronic and piezoelectric devices [24,25] due to its piezoelectric and optoelectric properties. The numerical study showed that as ZnO dielectric permittivity is close to those of the 0169-4332/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.apsusc.2013.04.070