Anioonpolümerisatsiooniga

Anioonpolümerisatsiooniga is a process used in polymer chemistry to create polymers through a chain-growth mechanism involving anionic intermediates. This method is a type of addition polymerization where the active center is an anion. The process typically begins with an initiator that generates a carbanion or another strongly nucleophilic species. This anionic initiator then attacks a monomer molecule, which must contain an electron-withdrawing group to stabilize the resulting carbanion. Common monomers for anionic polymerization include vinyl monomers like styrene, butadiene, and acrylates, as well as cyclic ethers and epoxides.

The chain propagation step involves the anionic active center reacting with successive monomer units, extending the polymer chain. The anionic species remains at the end of the growing chain, facilitating further addition. The reaction continues until all available monomer is consumed or until a terminating agent is introduced. One of the key advantages of anionic polymerization is its ability to achieve very high molecular weights and narrow molecular weight distributions, often resulting in polymers with well-defined structures. This control over polymer architecture allows for the synthesis of specialized materials with tailored properties.

Anionic polymerization is often carried out under strict conditions, typically in non-polar or polar aprotic solvents and at low temperatures, to prevent side reactions such as proton transfer or chain termination by impurities. The absence of terminating agents in many anionic polymerizations leads to "living polymerization," where the active centers remain at the chain ends even after monomer depletion, allowing for controlled block copolymer synthesis.