Complexes based on alkylboranes and α,β-unsaturated carbonyl compounds as bicomponent transfer agents for free-radical polymerisation

The free-radical polymerisation of several monomers (styrene, ethyl acrylate, methyl methacrylate) was carried out in the presence of complexes based on alkylboranes and α,β-unsaturated carbonyl compounds with a view of determining whether such complexes could function as transfer agents. Methyl vinyl ketone 1 or acrolein used in combination with triethylborane 2 exhibited transfer coefficients in the range of 0.25-1.24 in the polymerisation of the three monomers mentioned above. Conversely, associating 2 with cyclohex-2-one, and 3-methyl but-3-en-2-one was found inefficient, the 3-methyl but-3-en-2-one/2 complex being useful only with styrene. Attempts involving methyl vinyl ketone associated with either butyldichloroborane or diethylmethoxyborane failed to produce transfer in free-radical polymerisation.