A developed nanomechanical analysis of atomic force microscopy (AFM) based on the JKR theory has been applied to butyl rubber; isoprene-co-isobutylene rubber (FIR, butyl rubber). The force-deformation (F-S) plots converted from force-distance curves of IIR varied with several experimental conditions, i.e., temperature, scan velocity and maximum loading force. We analyzed the plots by the JKR analysis referring to the 'two-points method' proposed by Walker and co-workers. It was found that the apparent Young's modulus and adhesive energy obtained from the method revealed well-defined appearance when plotted against maximum sample deformation. In conclusion, the 'time-temperature-stress superposition principle', which is one of the major characteristics of viscoelastic materials, proved to be valid even at nanometer scale. (C) Koninklijke Brill NV, Leiden, 2009