The adhesion and fracture of styrene‐acrylonitrile random copolymer and poly(methyl methacrylate) (PMMA/SAN) laminates were studied. They showed a drastic transition from brittle to ductile on varying the acrylonitrile (AN) content in SAN, with changes in the fracture mode from interfacial failure to cohesive fracture. Energy‐filtering transmission electron microscopy (EFTEM) and scanning electron microscopy (SEM) with an in‐lens detector system were employed to study the interface and adhesion of the laminates. The effect of the AN content in SAN on the PMMA/SAN interfacial structures could be revealed by imaging of the interfaces using elemental mapping and electron energy loss spectroscopy (EELS). The in‐lens detector system in the SEM enabled the differentiation of thin interfaces with poor adhesion strength, yielding smooth and flat fracture surfaces, where numerous nanosized fibrils were formed normal to the surfaces.
