Dynamic moduli mapping of rubber blends by nanorheological atomic force microscopy

Abstract

The miscibility between two polymer species is important not only from a scientific viewpoint but also from an industrial perspective. The information on the morphology is not sufficient to understand their mixed states, and submicron-scale material properties must be clarified. A unique nanorheological atomic force microscopy (AFM) technique was utilized in this study to investigate the nature of a styrene-butadiene rubber (SBR)/butadiene rubber (BR) partially miscible polymer blend. The blend seemed to be immiscible according to scanning transmission electron microscopy and conventional AFM techniques. However, when both the storage modulus and loss modulus for the blends were compared with those for the homopolymers by using nanorheological AFM, values for both the SBR-rich and BR-rich regions did not coincide with those for the pure components. In particular, the BR-rich region, which might contain SBR due to their partial miscibility, exhibited a dynamic heterogeneity, where the frequency responses were much more complicated than those of the BR homopolymer, though differential scanning calorimetry measurement could not detect it as the change of glass-transition temperature.