The simplest case refers to the formation of a strictly linear polymer by the reaction (usually by condensation) of two monomers in equimolar quantities.
If one monomer is present in stoichiometric excess, then the equation becomes[3] The effect of the excess reactant is to reduce the degree of polymerization for a given value of p. In the limit of complete conversion of the limiting reagent monomer, p → 1 and Thus for a 1% excess of one monomer, r = 0.99 and the limiting degree of polymerization is 199, compared to infinity for the equimolar case.
Monomers with functionality greater than two will introduce branching into a polymer, and the degree of polymerization will depend on the average functionality fav per monomer unit.
For chain-growth polymerization or for branched polymers, the Đ can be much higher.
In practice the average length of the polymer chain is limited by such things as the purity of the reactants, the absence of any side reactions (i.e. high yield), and the viscosity of the medium.