Dispersion Characterization in Layered Double Hydroxide/Nylon 66 Nanocomposites Using FIB Imaging Y. D. Zhu, 1 G. C. Allen, 1 J. M. Adams, 2 D. Gittins, 3 M. Herrero, 4 P. Benito, 4 P. J. Heard 1 1 Interface Analysis Center, University of Bristol, Bristol BS2 8BS, United Kingdom 2 School of Engineering and Computer Science, University of Exeter, Exeter EX4 4QF, United Kingdom 3 Performance Minerals and Pigments, Central R&D, IMERYS Minerals Ltd., Par Moor Center, St. Austell, PL24 2SQ, United Kingdom 4 Departamento de Quı ´mica Inorga ´nica, Universidad de Salamanca, 37008 Salamanca, Spain Received 14 November 2007; accepted 11 January 2008 DOI 10.1002/app.28028 Published online 19 March 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Layered double hydroxides (LDHs), a newly emerging 2D host material, consist of cationic brucite-like layers and exchangeable interlayer anions. In this work, the morphology and dispersion of LDH particles in LDH/ Nylon 66 (salt) nanocomposites has been investigated using focused ion beam (FIB) techniques, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The FIB images show that LDHs are present in the poly- mer phase dispersed to different degrees, with partial intercalation, exfoliation, and aggregation all being observed. The most even dispersion was achieved in nano- composites with the lowest loading (0.5 wt % LDH). Resid- ual tactoids and agglomerates were most common in the samples made with the highest concentration of LDHs studied here (5 wt %). The dispersion observed using FIB was consistent with TEM and XRD analysis, yet this tech- nique had significant benefits in terms of time and simplic- ity over these ‘‘conventional’’ technologies. Ó 2008 Wiley Periodicals, Inc. J Appl Polym Sci 108: 4108–4113, 2008 Key words: Nylon 66; LDH; nanocomposite; dispersion; FIB INTRODUCTION Since the Toyota Research Group carried out the ini- tial work to produce Nylon 6/clay nanocompo- sites, 1,2 the use of polymeric nanocomposites in vari- ous engineering applications has become state-of-the- art because these materials have high potential for delivering very significant property improvements while adding only small amounts of nanoparticles to polymer matrices. These improvements include mod- ulus, strength, heat resistance, and reductions of gas permeability and flammability, 3–5 all of which can be achieved with little increase in weight, significant in many applications in vehicle transports for example. As an alternative to the natural layered silicate clay (montmorillonite) commonly used for the prep- aration of polymeric nanocomposites, a new class of nanocomposites employs synthetic nanoparticles, layered double hydroxides (LDHs), with opposite charge to montmorillonite, i.e., the layers are cationic rather than anionic. Nanocomposites based on LDHs have recently generated interest from researchers due to their special properties in a wide range of application such as catalysis, adsorption, structural applications, and drug delivery. 6,7 LDHs have positively charged hydroxide layers and interlayers containing exchangeable anions and water mole- cules. Compositions can be expressed as: [M 21 1-x M 31 x (OH) 2 ] intra [A m2 x/m nH 2 O] inter , where M 21 and M 31 are metal ions, A is the anion, and intra and inter denote the intralayer domain and the interlayer space, respectively. LDH layers consist of edge- sharing octahedra; each of the octahedra having a central cation coordinated with six hydroxyl groups. The layers are 0.48–0.49 nm thick 8,9 and their planar dimensions can be tuned by properly adjusting the synthesis conditions. The most important features of LDHs are their large variety of compositions and the tunable layer charge density. 10 It has been commonly agreed that particle disper- sion plays an important role in the improvement of mechanical and other properties in nanocomposites, because a high degree of dispersion ensures maxi- mum interface area and the maximum impact on polymer crystallinity and structure. Generally, the dispersion of particles in the polymer matrix is char- acterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). 11–14 SEM can give a general Correspondence to: G. C. Allen (g.c.allen@bristol.ac.uk). Contract grant sponsor: MEC and MEC; contract grant number: MAT2006-10800-C02-01. Contract grant sponsors: Materials Centre South West- Great Western Research; Imerys Minerals Ltd.; contract grant numbers: (MCyT) MAT2006-10800-C02-1; (JCyL) SA030/03; and ERDF. Journal of Applied Polymer Science, Vol. 108, 4108–4113 (2008) V V C 2008 Wiley Periodicals, Inc.