Polycondensaatiomenetelmässä

Polycondensation is a type of step-growth polymerization reaction. In this process, monomers containing at least two reactive functional groups react with each other to form larger molecules, releasing small molecules as byproducts. These byproducts are typically water, methanol, or hydrogen chloride. The reaction proceeds in a stepwise manner, with oligomers and polymers forming from the initial monomers.

Key characteristics of polycondensation include the stepwise growth of polymer chains and the elimination of a small molecule during each linkage formation. This is in contrast to chain-growth polymerization, where monomers add to a growing chain end rapidly. Common functional groups involved in polycondensation are hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), and halide (-Cl).

Examples of polymers produced via polycondensation include polyesters, polyamides (like nylon), polycarbonates, and polyurethanes. For instance, the formation of polyester involves the reaction between a diol and a dicarboxylic acid, with the elimination of water. Similarly, polyamides are formed from diamines and dicarboxylic acids, also releasing water.

The molecular weight of the polymer in a polycondensation reaction depends on the extent of reaction and the stoichiometry of the monomers. Achieving high molecular weight polymers often requires near-complete conversion of the monomers and precise control over the monomer ratio. Reaction conditions such as temperature, catalyst presence, and removal of the byproduct can significantly influence the rate and outcome of the polycondensation process.