Dicyanate-clay nanocomposites comprising a dicyanate resin and a type of organically modified clay were prepared and characterized, and their thermomechanical properties were investigated. The organically modified clay had silicate layers of nanometer size intercalated with an organic modifier, which improved the compatibility between the clay and organic materials, such as dicyanate resins. Dynamic mechanical analysis was performed to investigate the thermomechanical properties of the dicyanate-clay nanocomposites containing various amounts of the clay. The storage modulus of the nanocomposites below their glass-transition temperatures slightly increased with increasing clay content. The glass-transition temperature of the dicyanate-clay nanocomposites increased with increasing clay content. The nanostructures of the dicyanate-clay nanocomposites were characterized by transmission electron microscopy and X-ray diffraction analysis. (C) 2003 Wiley Periodicals, Inc.