Initiators

Initiators are substances or events that start a process, triggering a reaction or sequence of reactions. They are used across science and industry to begin chemical, physical, or biological processes. Initiators are distinguished from catalysts in that they are consumed during the reaction and often generate reactive species that propagate the process.

In polymer chemistry, initiators start polymerization. Free-radical initiators decompose to form radicals that add to monomers, creating growing chains. Common examples include thermal initiators such as benzoyl peroxide and AIBN, as well as redox systems that react at room temperature. Photoinitiators absorb light and rapidly generate radicals or cations, enabling rapid curing of coatings and adhesives. Widely used photoinitiators include Irgacure derivatives and benzoin ethers. The choice of initiator affects polymerization rate, molecular weight, and polymer architecture.

In resins and coatings, latent or initiator-triggered curing systems allow controlled setting, often requiring activation by light, heat, or a catalyst. This enables on-demand curing and spatial control in processes like 3D printing and surface coatings.

In biology and biochemistry, initiation refers to the beginning of processes such as transcription or translation, driven by initiation factors and enzymes that assemble the necessary machinery at a gene or mRNA. In catalysis and materials science, initiation steps may involve the formation of an active catalytic species or the first reactive event in a cycle.

Initiators are classified by mechanism (radical, ionic, photoinitiators, enzymatic) and by activation method (heat, light, chemical redox). They can pose hazards due to exothermic decomposition or sensitivity to oxygen and moisture, requiring careful storage and handling.