Crystallization behavior of nano-composite based on poly(vinylidene fluoride) and organically modified layered titanate Kumiko Asai a , Masami Okamoto a, * , Kohji Tashiro b a Advanced Polymeric Nanostructured Materials Engineering, Graduate School of Engineering, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468 8511, Japan b Department of Future Industry-Oriented Basic Science and Materials, Graduate School of Engineering, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468 8511, Japan article info Article history: Received 29 February 2008 Received in revised form 4 July 2008 Accepted 19 July 2008 Available online 29 July 2008 Keywords: Poly(vinylidene fluoride) Nano-composites Crystallization abstract To understand the effect of the nano-filler particles on the crystallization kinetics and crystalline structure of poly(vinylidene fluoride) (PVDF) upon nano-composite formation, we have prepared PVDF/ organically modified layered titanate nano-composite via melt intercalation technique. The layer titanate (HTO) is a new nano-filler having highly surface charge density compared with conventional layered silicates. The detailed crystallization behavior and its kinetics including the conformational changes of the PVDF chain segment during crystallization of neat PVDF and HTO-based nano-composite (PVDF/HTO) have been investigated by using differential scanning calorimetric, wide-angle X-ray diffraction, light scattering, and infrared spectroscopic analyses. The neat PVDF predominantly formed a-phase in the crystallization temperature range of 110–150  C. On the other hand, PVDF/HTO exhibited mainly a-phase crystal coexisting with g- and b-phases at low T c range (110–135  C). A major g-phase crystal coexists with b- and a-phases appeared at high T c (¼140–150  C), owing to the dispersed layer titanate particles as a nucleating agent. The overall crystallization rate and crystalline structure of pure PVDF were strongly influenced in the presence of layered titanate particles. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Over the last few years, the utility of inorganic nanoscale particles as filler to enhance the polymer performance has been established. Of particular interest is recently developed nano- composite technology consisting of a polymer and organically modified layered filler (organo-clay) because they often exhibit remarkably improved mechanical and various other materials’ properties as compared with those of virgin polymer or conven- tional composite (micro/macro-composites) [1–5]. These concur- rent property improvements are well beyond what can be generally achieved through the micro/macro-composites’ preparation. The effect of organo-clay on the crystal structure and poly- morphism of the matrix semi-crystalline polymer has been inves- tigated in nano-composites. The crystallization rate of nylon 6 was enhanced dramatically in the presence of clay particles as revealed from light scattering experiments [6]. Nylon 6 was crystallized extensively in the g-form in the nano-composite because of the epitaxial crystallization, which was also revealed from the transmission electron microscopic images. Mathias et al. [7] have investigated nylon 6 nano-composite using 15 N nuclear magnetic resonance and concluded that the clay stabilizes the g-phase of nylon 6. A new polymorph of poly(vinylidene fluoride) (PVDF) was introduced in PVDF-based nano-composites [8–11]. The phase is preferentially crystallized in the b polymorph in the presence of the organically modified clay (organo-clay). They reported that similar crystal lattices between clay and the b polymorph, and the large flat surface of the clay are the key factors to interact between polymer and inorganic materials [11]. Recently, a full analysis of the crys- tallization of PVDF in nano-composites has been done by Dillon et al. [12,13]. Using Fourier transform infrared spectroscopy (FTIR), they reported that a-form coexists with b- and g-phases, and the amount of b-phase increases with increasing clay content. The interaction of an inorganic phase of the organo-clay with the semi-crystalline polymer, the loading amount of the interface, shape, dimension, and surface properties of the layered filler can potentially change the crystallization kinetics and the crystalline morphology of the matrix polymer [14–16]. Despite extensive studies of the polymer crystallization in nano- composite systems, the mechanism underlying of the different polymorphisms is not very well explored in the literature. * Corresponding author. Tel.: þ81 52 809 1861; fax: þ81 52 809 1864. E-mail address: okamoto@toyota-ti.ac.jp (M. Okamoto). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2008.07.037 Polymer 49 (2008) 4298–4306