Towards the molecular workshop: entropy-driven designer molecules,   entropy activation, and nanomechanical devices
  We introduce some basic concepts for designer molecules with functional units which are driven by entropic rather than energetic forces. This idea profits from the mechanically interlocked nature of topological molecules such as catenanes and rotaxanes, which allows for mobile elements whose accessible configuration space gives rise to entropic intramolecular forces. Such entropy-driven designer molecules open the possibility for externally controllable functional molecules and nanomechanical devices. 
Andreas Hanke, Ralf Metzler