avamisrõngapolümerisatsioon

Avamisrõngapolümerisatsioon, also known as ring-opening polymerization, is a polymerization mechanism where cyclic monomers open to form a linear polymer chain. This process differs from chain-growth polymerization where monomers add to a growing chain by forming new bonds without breaking existing ones within the monomer itself. In ring-opening polymerization, the strain energy within the cyclic monomer is a driving force for the reaction.

Several types of ring-opening polymerization exist, including cationic, anionic, and radical ring-opening polymerization, depending on the initiator used. Coordination ring-opening polymerization is also common, particularly for cyclic ethers and esters, often employing metal-based catalysts. The mechanism involves the activation of the cyclic monomer, followed by ring opening and propagation of the polymer chain.

Common examples of polymers produced via ring-opening polymerization include poly(ethylene oxide) from ethylene oxide, poly(lactide) from lactide, and poly(caprolactone) from caprolactone. These polymers find applications in diverse fields such as biodegradable plastics, medical devices, adhesives, and coatings. The control over molecular weight and polymer architecture can be achieved by carefully selecting reaction conditions and initiators.