Films of soluble collagen extracted from rat-tail tendon were studied at the solid-solution interface, and the surface energy of the films was evaluated. The films transferred onto solid substrates using the Langmuir-Blodgett film (LB film) technique were characterized using Fourier transform IR attenuated total reflectance spectroscopy and atomic force microscopy. The properties of the protein in contact with different structure modifiers like basic chromium sulfate (BCS) and formaldehyde (HCHO) were analyzed for the effect of various tanning agents on the protein structure. The thermal properties of the films were studied using differential scanning calorimetry. The results show that the film of collagen treated with BCS exhibits an increase in the peak temperature and enthalpy changes compared to the pure collagen as well as the protein with HCHO. These differences are attributed to the changes in the crosslinks arising from both coordinate-covalent and covalent interactions, respectively. The atomic force micrographs showed an increase in order for the collagen film with BCS compared to the HCHO treated analogue. A similar trend is seen in the surface energy parameters of the protein films on solid surfaces on reacting with BCS and HCHO, suggesting a molecular level ordering process in collagen assemblies. (C) 2004 Wiley Periodicals, Inc.