2017 Elsevier Ltd. All rights reserved. Entangled motifs where components are mechanically interlocked are commonly encountered in polymeric networks and are analogous to supramolecular species containing mechanical bonds such as rotaxanes, catenanes, and molecular knots. The mechanically interlocked polymeric motifs include polycatenanes, polyrotaxanes, and interpenetrated nets. Interpenetration is a common occurrence in crystalline networks and has been increasingly encountered coordination networks have gained widespread attention in the literature. This chapter will serve to address several important aspects of interpenetrated network crystals. First, the concept of mechanical interlocking in small molecular assemblies will be discussed with specific types of architectures examined. The terminology involved with describing nets and their entanglements will be briefly reviewed in order for the reader to comprehend the remainder of the chapter. Entangled networks will then be addressed with regards to polycatenation, polythreading, and self-penetration, and how they differ from structural interpenetration. Different dimensionalities of interpenetrating nets are discussed in detail, specifically examining the structural components lending to the formation of each 1D, 2D, and 3D interpenetrated networks. The consequences of interpenetration on the physical properties of networks will be briefly discussed. Interpenetration control will be discussed thoroughly in terms of structural and design aspects of network materials with extensive examples from the recent literature provided. Finally, we will give an overview of some of the emerging applications where interpenetrated networks have found utility.
