The interfacial region between fillers and polymer matrix in the nanocomposite materials is believed to be one of the key morphological elements to govern their mechanical properties. The direct visualization of such interfacial region, “interphase region” for short, has been a subject for many years. Transmission electron microscopy (TEM) is a powerful tool to visualize nano-scale polymeric morphologies, however, because the interphase region consists of the same polymeric species as the matrix, no electron contrast of the interphase can be found under TEM. Atomic force microscopy (AFM), on the other hand, gives clear and sharp contrast due to mechanical properties: force-curve measurements are carried out at each point of the AFM image. In other words, each pixel has physical quantities, e.g., elastic modulus, adhesion work function etc., in AFM. It has been shown that there exist regions around the fillers with higher elastic modulus (than the rubbery matrix), indicating the presence of the interphase region. However, because the mechanical properties can be easily affected by the structures underneath the measurement points where the force-curve measurements are carried out, the higher elastic region around the fillers may not necessarily reflect the true interphase region.<br/> <br/>In the present work, we used transmission electron tomography (TEMT), a three-dimensional (3D) visualization method at nanometer scale, to observe internal 3D structure of rubber nano-composite, which are combined together with AFM. Namely, the two imaging techniques were carried out at exactly the same portion of the rubber nano-composite. In doing so, it became possible, for the first time, to accurately determine the elastic modulus from the AFM with the knowledge of internal (underneath) structures. Thus, the true interphase regions, if any, may be obtained from the combined technique of TEMT and AFM. Details will be discussed at the conference time.

Direct visualization of Interphase region between fillers and matrix in rubber composites observed by electron tomography with mechanical mapping

256th National Meeting (2018)

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