This book presents an overview of polymer nanocomposites for use in various high-temperature applications. Specifically, it focuses on the structure and physical properties of nanocomposites based on heterocyclic matrices derived from nitrile monomers such as cyanate esters or phthalonitriles. Due to increasing interest in new heat-resistant, lightweight materials for use in extreme conditions, such as in aeronautics, microelectronics, and various industrial machinery, the high thermal stability of heterocyclic polymer networks, in particular, has attracted much attention from materials...