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According to IUPAC, the functionality of a monomer is defined as the number of bonds that a monomer's repeating unit forms in a polymer with other monomers. Thus in the case of a functionality of f = 2 a linear polymer is formed by polymerizing (a thermoplastic). Monomers with a functionality f ≥ 3 lead to a branching point, which can lead to ...
The functionality of a monomer molecule is the number of functional groups which participate in the polymerization. Monomers with functionality greater than two will introduce branching into a polymer, and the degree of polymerization will depend on the average functionality f av per monomer unit.
The functionality of a monomeric structural unit is defined as the number of covalent bonds which it forms with other reactants. [1] A structural unit in a linear polymer chain segment forms two bonds and is therefore bifunctional , as for the PET structural units above.
A monomer (/ ˈ m ɒ n ə m ər / MON-ə-mər; mono-, "one" + -mer, "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization.
A monomer with functionality 3 has 3 functional groups which participate in the polymerization. This will introduce branching in a polymer and may ultimately form a cross-linked macrostructure. The point at which this three-dimensional 3D network is formed is known as the gel point , signaled by an abrupt change in viscosity.
Condensation polymerization is an important class of step-growth polymerization, which is formed simply by the reaction of two monomers and results in the release of a water molecule. [4] Since these polymers are typically made up of two or more monomers, the resulting end groups are from the monomer functionality.
A general image of a multifunctional branch unit, , reacting with bifunctional monomers with A and B functional groups to form a step-growth polymer. The Flory–Stockmayer Theory predicts the gel point for the system consisting of three types of monomer units [1] [5] [6] [7]
The degree of branching that occurs during polymerisation can be influenced by the functionality of the monomers that are used. [6] For example, in a free radical polymerisation of styrene , addition of divinylbenzene , which has a functionality of 2, will result in the formation of branched polymer.