Metastable mesophases

Mesophases are briefly summarized and defined on a uniform basis, making use of order and mobility parameters. A schematic one‐component phase diagram is then reviewed that includes equilibrium as well as nonequilibrium phases. Assuming only five condensed phases (crystal, melt, glass, mesophase, and mesophase glass), fifteen different phase areas exist with simultaneous presence of up to three phases. Examples of all phase areas are documented with results from our laboratory. This scheme can be extended to more components and more than these five phases and produces then many more possible phase areas than can be handled experimentally at the present.