To investigate the effects of reaction conditions on a intercalation between gelatin and montmorillonite (MMT) and thermodynamical impact of the intercalation, a series of gelatin/MMT hybrids were prepared by changing the reaction conditions (weight ratio of gelatin and MMT, pH, concentration of gelatin solution and MMT suspension, and reaction temperature). The hybrids were characterized by X-ray diffraction, transmission electron microscopy, atomic absorption spectroscopy, and thermogravimetric analysis. The results showed the intercalation between gelatin and MMT, which was a faster process than the melt intercalation of some synthetic macromolecules such as polystyrene, achieved a thermodynamically stable state in 5 min. All the other reaction conditions, except reaction temperature, affected the intercalation between gelatin and MMT. The reaction was driven by enthalpy. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 54-59, 2013