Porraspolymeerisaation

Porraspolymeerisaatio, a Finnish term, translates to step-growth polymerization in English. This is a type of polymerization reaction where monomers, which are small molecules, react with each other to form larger repeating units and thus a polymer. Unlike chain-growth polymerization, where monomers add to a growing chain one by one, step-growth polymerization involves reactions between functional groups on the monomers. These reactions can occur between monomer A and monomer B, or between two molecules of the same monomer if it possesses two different functional groups (e.g., A-B type monomer).

The key characteristic of step-growth polymerization is that the molecular weight of the polymer increases gradually throughout the reaction. Initially, the reaction mixture consists mainly of monomers, then dimers, trimers, and longer oligomers are formed. High molecular weight polymers are only achieved in the later stages of the reaction when these oligomers start reacting with each other. A byproduct, often a small molecule like water or HCl, is typically released with each step of the polymerization.

Common examples of polymers formed through step-growth polymerization include polyesters, polyamides (like nylon), polyurethanes, and polycarbonates. These polymers are widely used in various applications, from textiles and packaging to engineering plastics and coatings, due to their diverse properties achievable through different monomer selections. The reaction kinetics and the efficiency of the functional group reactions are crucial factors determining the final molecular weight and properties of the polymer.