Allylpolymerisierung

Allylpolymerisation is a type of polymerisation reaction involving monomers that contain allyl groups. An allyl group is a hydrocarbon group with the formula CH2=CHCH2-. This functional group is characterized by a double bond adjacent to a methylene group. Unlike vinyl monomers, which readily undergo chain-growth polymerisation through the double bond, allyl monomers exhibit slower and more complex polymerisation behavior.

The primary challenge in allylpolymerisation is chain transfer, also known as degradative chain transfer. During the propagation step, a radical can abstract a hydrogen atom from the allylic position of the monomer or a growing polymer chain. This abstraction creates a resonance-stabilized allyl radical, which is less reactive than the original propagating radical. This resonance stabilization makes it difficult for the allyl radical to initiate new polymer chains, leading to a low molecular weight and incomplete conversion of the monomer.

Despite these challenges, allylpolymerisation can be achieved under specific conditions, often requiring high initiator concentrations or elevated temperatures to overcome the slow propagation rate. Various allyl monomers, such as allyl chloride, allyl alcohol, and allyl methacrylate, can be polymerised. The resulting polymers often possess unique properties due to the presence of residual unsaturation in the polymer backbone, which can be used for further crosslinking or modification. Allyl polymers find applications in areas such as coatings, adhesives, and specialty resins.