Solids: Thermodynamics and Bonding

· Polymer molecules can form three-dimensional covalently bonded networks. Phenol formaldehyde is the example shown in the diagram.
· The units of this type of structure need to be poly-functional, i.e. able to bond covalently to several other groups. The formation of covalently bonded three-dimensional structures requires a functionality of three or more.
· Diamond could be thought of a the prototype of this type of structure.

From: van Vlack, "Elements of Materials Science and Engineering," Addison Wesley (1990)