polymerisatiestarten

Polymerisation initiation refers to the process that begins the formation of polymers, where monomers—small molecules—link together to create long chains. This stage is critical in polymer chemistry as it sets the foundation for the entire polymerisation reaction. Initiation typically involves the activation of a monomer or initiator species, which generates reactive intermediates capable of propagating the polymer chain.

In free-radical polymerisation, the most common initiation method, an initiator—such as benzoyl peroxide or azobisisobutyronitrile—decomposes upon heating or exposure to light, producing free radicals. These radicals then abstract a hydrogen atom from a monomer, forming a new radical species that can react with additional monomers, initiating chain growth. The efficiency of initiation depends on factors like temperature, initiator concentration, and the presence of inhibitors or retarders.

In ionic polymerisation, initiation involves the formation of cationic or anionic species, which react with monomers to generate active centres. For example, in cationic polymerisation, a Lewis acid (such as aluminium chloride) can activate a monomer, creating a carbocation that begins chain propagation. Similarly, anionic initiators, such as butyllithium, generate carbanions that react with monomers to start polymer growth.

In living polymerisation systems, initiation is designed to be fast and quantitative, ensuring minimal chain termination or transfer. This allows for precise control over molecular weight and polydispersity, making it valuable for synthesising well-defined polymers. The choice of initiation method depends on the desired polymer properties, monomer type, and reaction conditions. Proper initiation ensures efficient polymerisation and influences the final polymer’s structure and functionality.