The addition of nanomaterials into a polymer matrix at low concentrations (~0.2wt%) can lead to dramatic changes in the viscoelastic, mechanical, electrical, and optical properties of the material, enabling a wide variety of applications in structural, electronic, and biological implant materials and devices. Although the bulk properties of the composites can be easily measured through traditional means, much is still unknown on how the local polymer properties change approaching the interface of the nanoparticles, especially for polymers in the rubber regime. Previous work has used atomic force microscopy (AFM) to measure the local elastic modulus at this interphase, but time dependent viscoelastic properties of polymers present more challenges in capturing quantitative frequency/time resolved responses. A quantitative technique to measure viscoelastic properties at the nanoscale for these composites using a modified Quantitative Nanomechanical Mapping (QNM) AFM technique has been developed. An oscillating cantilever indents into an elastomer in a sinusoidal motion and the resulting force is recorded. From the phase lag between these two responses, the viscoelastic properties can be measured. The accuracy of this method has been compared to oscillatory data of the bulk material using dynamic mechanical analysis. The method can be applied to biphasal systems to measure how the viscoelastic properties change at the interphase. Model composite samples made from carbon-rubber “sandwich” structures have been investigated for quantitative interphase measurements. These structures minimize the geometrical complexity found in bulk nanocomposites, allowing the isolation of the interphase effect. Various geometries can then be explored to understand their influence on locally changing polymer properties. The goal is to apply these results to computational models and data mining tools to find guiding relationships in material physics and to enable targeted material design.