Polyaddition

Polyaddition is a chemical process in which simpler chemical compounds, known as monomers, are joined together by reactions between their functional groups to form large, polymeric molecules, known as macromolecules. In contrast to polymerisation, in which the monomers are joined together by the reaction of C=C double bonds, in polyaddition the linking takes place through the migration of hydrogen atoms (H).

Another important distinguishing feature compared with polycondensation is that in polyaddition no low-molecular-weight compounds, such as water or small molecules, are eliminated. In polycondensation, by contrast, such low-molecular-weight substances often arise as by-products, which are released during the reaction. Polyaddition thus enables the formation of polymers without the creation of by-products, which is advantageous in many applications.