Kondensaatiokytkentä

Kondensaatiokytkentä, known in English as condensation coupling or condensation polymerization, is a chemical reaction where monomer units join together to form a polymer, releasing a small molecule as a byproduct. This small molecule is typically water, but can also be other substances like methanol or hydrogen chloride. The process is essentially the reverse of hydrolysis, where water breaks down a polymer.

In condensation polymerization, each monomer molecule must possess at least two functional groups. These functional groups react with each other, forming a new covalent bond and eliminating the small molecule. For example, in the formation of polyester, a dicarboxylic acid and a diol react. The hydroxyl group of the diol reacts with the carboxyl group of the dicarboxylic acid, forming an ester linkage and releasing a water molecule. This process repeats, with monomers adding to the growing chain, leading to a high molecular weight polymer.

Common polymers formed through condensation include polyesters, polyamides (like nylon), polycarbonates, and polyurethanes. These materials find widespread applications in textiles, plastics, adhesives, and coatings due to their diverse properties. The specific type of functional groups present on the monomers dictates the resulting polymer's characteristics, such as its strength, flexibility, and thermal stability. Understanding condensation coupling is fundamental to polymer chemistry and the design of new materials.