The effects on clay exfoliation of organic modification of montmorillonite (MMT) and the nature of the catalyst used during the synthesis and curing of a MMT modified phenolic resol resin were investigated. The impact on the final properties of other parameters such as reactivity ratio and temperature of condensation were also analyzed in order to optimize the conditions to prepare a customized organoclay-based nanocomposite. Nanocomposites were analyzed by means of wide angle X-ray scattering (WAXS), optical microscopy (TOM), and atomic force microscopy (AFM) techniques. The formation of either intercalated or quasi-exfoliated structure was assessed in some systems. Thermal and mechanical properties of the cured composites were evaluated and correlated to their morphologies. More homogenous clay dispersion was achieved for composites prepared with aminoacid-modified MMT, triethylamine (TEA) as catalyst, formaldehyde/phenol molar ratio (F/P) 2.0, and curing at 80 degrees C. POLYM. ENG. SCI., 2012. (C) 2011 Society of Plastics Engineers