## Wikipedia - Structural unit functionality, $$f$$

of a monomer
https://doi.org/10.1351/goldbook.FT07505
Number of covalent bonds that a @M04019@ or monomeric unit in a macromolecule or @O04286@ can form with other reactants.
Notes:
1. There are no monofunctional monomers.
2. If $$f = 2$$, a @L03546@ macromolecule or a @M03662@ can be formed.
3. If $$f > 2$$, a branch point can be formed leading to a branched macromolecule, a @NT07562@ or a micronetwork.
4. Ethene and ethylene glycol are examples of difunctional monomers, glycerol is an example of a trifunctional @M04017@, and divinylbenzene and pentaerythritol are examples of tetrafunctional monomers.
Source:
PAC, 2007, 79, 1801. (Definitions of terms relating to the structure and processing of sols, gels, networks, and inorganic-organic hybrid materials (IUPAC Recommendations 2007)) on page 1805 [Terms] [Paper]