Preparation and Characterization of Layered Double Hydroxides – PMMA Nanocomposites by Solution Polymerization Guo-An Wang, 1 Cheng-Chien Wang, 2 and Chuh-Yung Chen 1,3 Layered double hydroxides (LDH) – poly(methyl methacrylate) (PMMA) intercalated-exfo- liated nanocomposites were synthesized by solution polymerization of methyl methacrylate (MMA) in the presence of aminobenzoate organically-modified LDH. Preparations of 4-aminobenzoate organically modified LDHs were carried out by applying a chemical co- precipitation reaction. Structural and compositional details of LDH-AB were obtained with Fourier transformed infrared (FT-IR) spectroscopy, 27 Al magic-angle spinning nuclear magnetic resonance ( 27 Al MAS NMR), elemental analysis (EA), inductively coupled plasma (ICP) atomic absorption spectrometry and X-ray diffraction (XRD). The morphology of the LDH-AB in the PMMA matrix was identified by employing transmission electron microscopy (TEM), XRD, and UV/visible transmission spectroscopy. The thermal properties of the nanocomposites were enhanced and their Tg values as well as the decomposition temperatures shifted to a high temperature region as identified by the differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). For example, the Tg value and the decom- position temperature of the nanocomposites with 6.4% LDH-AB increased by 19 °C and 24 °C, respectively. KEY WORDS: Nanocomposites; layered double hydroxides; poly(methyl methacrylate); FT-IR; 27 Al magic-angle spinning NMR; TGA; DSC. 1. INTRODUCTION In recent years, nanocomposite materials have attracted considerable research interest. Organic– inorganic nanocomposites indicate that the dimen- sion of the inorganic dispersed phase has at least one-dimension less than 100 nm [1–3]. Most research during the past decade regularly utilized clays as an inorganic dispersed phase because they exhibit diverse morphologies with a large aspect ratio and considerable ion exchange capacity. Polymer-clay nanocomposites possess, by virtue of their large interfacial area per volume ratio, unique properties such as improved mechanical strength [4, 5], thermal stability [5, 6], anti-flammability [7], ionic conductiv- ity [8], and gas permeability [9]. From a structural viewpoint, the layers of clay that are dispersed in the polymer matrix separate into intercalated and exfoliated nanocomposites. Interca- lated nanocomposites have polymer chains that penetrate into the interlayer gallery; and, the distance between the layers is increased without completely separating the layers. Exfoliated nanocomposites are defined as having insufficient attractions between each two-layer section. For this reason they cannot 1 Department of Chemical Engineering, National Cheng-Kung University, Tainan, 70148, Taiwan. 2 Department of Chemical Engineering, Southern Taiwan Uni- versity of Technology, Tainan, 710, Taiwan. 3 To whom correspondence should be addressed. E-mail: ccy7@ccmail.ncku.edu.tw Journal of Inorganic and Organometallic Polymers and Materials, Vol. 15, No. 2, June 2005 (Ó 2005) DOI: 10.1007/s10904-004-5541-x 239 1574-1443/05/0600-0239/0 Ó 2005 Springer Science+Business Media, Inc.