EFFECT OF ACETYL ACETONE ON RADICAL POLYMERIZATION OF VINYL MONOMERS INITIATED BY BENZOYL PEROXIDE

Abstract

The radical polymerization of styrene and methyl methacrylate (MMA) initiated by benzoyl peroxide (BР) with the addition of 10, 20, 50, and 80% of acetylacetone (AA) mixed with a monomer was studied. It was found that the rate of the polymerization process increases in the presence of a certain amount of AA in the system (³ 50% of the monomer). This is due to the fact that AA accelerates the decomposition of BP, while removing it from the system in the form of non-radical products, and the initiating function is performed by acetylacetonate radicals, which are formed upon interaction with BP. The incorporation of acac fragments into the polymer chain has been proved by IR and 1H NMR spectroscopy. It was found that these groups in the composition of the polymer interact with the p-system of benzene rings of polystyrene. The second reason for the accelerating action is the formation of complexes between the monomer and AA, in which the additive has an acceptor effect, leading to the facilitation of the breaking of double bonds in the monomer. It was shown that MMA has a stronger effect on AA polymerization, because forms stronger complexes with the enol form of AA, which requires a longer time for the radical to leave the complex. In this regard, during its polymerization, induction periods are observed, the duration of which is directly proportional to the concentration of AA in a mixture with MMA. It was revealed that another feature of the effect of AA on radical polymerization is its participation in chain transfer reactions, which does not decrease the rate of the process, but only leads to a decrease in the molecular weight of the products. This makes it an effective regulator of polymer molecular weights. The paper proposes a scheme for the polymerization of vinyl monomers, initiated by BP with the addition of AA.