Polüondensatsioon

Polüondensatsioon is a type of step-growth polymerization process where monomers react to form a polymer and a small molecule, such as water, methanol, or hydrogen chloride. This reaction occurs in a stepwise manner, with monomers reacting to form dimers, which then react to form trimers, and so on, until long polymer chains are formed. Each step of the polymerization involves the elimination of a small molecule.

The key characteristic of polycondensation is the formation of a byproduct. Unlike chain-growth polymerization, where monomers add to a growing chain without the release of any byproduct, polycondensation reactions involve the condensation of functional groups on the monomers. For example, if a diol and a dicarboxylic acid react, they form a polyester and release water. Similarly, diamines and dicarboxylic acids form polyamides (nylons) and release water.

The rate of polycondensation is generally slower than chain-growth polymerization and is often dependent on factors such as temperature, catalyst concentration, and the concentration of reactants. The molecular weight of the polymer increases gradually as the reaction proceeds. This process is widely used in the synthesis of important polymers like polyesters, polyamides, polycarbonates, and phenolic resins, which find applications in textiles, plastics, coatings, and adhesives. The purity of the monomers is crucial for achieving high molecular weight polymers in polycondensation reactions.