Characterization of poly(vinyl alcohol)/poly(ethylene glycol) hydrogels and PVA-derived hybrids by small-angle X-ray scattering and FTIR spectroscopy Herman S. Mansur * , Rodrigo L. Ore ´fice, Alexandra A.P. Mansur Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais, Rua Espı ´rito Santo, 35/28 Andar, 30160030 Centro, Belo Horizonte, MG, Brazil Received 15 June 2004; received in revised form 12 August 2004; accepted 17 August 2004 Abstract The purpose of this study is to develop novel poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) hydrogel blends and PVA-derived organic–inorganic hybrid materials and perform nanostructural characterizations. PVA and PEG hydrogels were prepared by dissolving the polymer in aqueous solution, followed by addition of glutaraldehyde (GA) chemical crosslinker. Hybrids were synthesized by reacting PVA in aqueous solution with tetraethoxysilane (TEOS). PVA/TEOS were also modified in the nanometer-scale by crosslinking with GA during the synthesis reaction. Hydrogels and hybrids were characterized by using small-angle X-ray scattering synchrotron radiation (SAXS) and Fourier transform infrared spectroscopy (FTIR). Thin film samples were prepared for SAXS experiments. SAXS results have indicated different nano-ordered disperse phases for hydrogels made of PVA, PEG, PVA/GA, PVA/PEG. Also, PVA/TEOS and PVA/TEOS/GA hybrids have indicated different X-ray scattering patterns. FTIR spectra have showed major vibration bands associated with organic– inorganic chemical groups present in the hybrid nanocomposites PVA/TEOS and PVA/TEOS/GA. PVA/PEG hydrogels and PVA-derived hybrid materials were successfully produced with GA crosslinking in nanometer-scale network. q 2004 Elsevier Ltd. All rights reserved. Keywords: Hybrids; Nanocomposite; Hydrogel 1. Introduction Recently, the field of material science has witnessed the emergence of both hydrogels and novel class of materials called organic–inorganic hybrids. Hydrogels and hybrid materials are of intensive interest in contemporary material chemistry as these materials have potential applications in biomedical devices, matrices for drug delivery systems, carrier for cells immobilization, carrier for signaling molecules, and bioseparation membranes [1–6]. The major driving forces behind the intense activities in this area are the new and different properties of these materials, which the traditional composites and conventional materials do not have. Hybrids would combine properties of organic polymers with ceramics. These different components can be mixed at length scales ranging from nanometer to micrometer, in virtually any ratio leading to the so-called hybrid organic–inorganic materials. They are also termed as ‘ceramers’ and ‘ormosils’ (organically modified silicates) or ‘ormocers’ (organically modified ceramics), which are normally nanocomposites [4]. The hybrids having such combined characteristics of organic and inorganic sub- stances promise new high performance or high functional materials to fully exploit this technical opportunity with benefits of the better of the two worlds. On the other hand, hydrogels are three-dimensional, hydrophilic polymeric networks capable of absorbing and retaining different amounts of water or biological fluids. The networks are insoluble due to the presence of chemical crosslinks (junctions, tie-points) or physical crosslinks (crystallites, entanglement), which permit hydrogels to be thermodyna- mically compatible with water [7–9]. As a result, in 0032-3861/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2004.08.036 Polymer 45 (2004) 7193–7202 www.elsevier.com/locate/polymer * Corresponding author. Tel.: C55-31-3238-1843; fax: C55-31-3238- 1815. E-mail address: hmansur@demet.ufmg.br (H.S. Mansur).