An acrylic monomer having βdiketonic moiety

i.e.3-acetyl-5-methyl-5-hexene-2

4-diketone(AMAA) was synthesized by reaction of acetylacetone and methacrylyl chloride in the presence of magnesium ethoxide.It has been found that AMAA is difficult to polymerize by free-radical initiation or heating due to the enol formating of βdiketonic moiety in the monomer.After the protection of the enol form in AMAA by treatment with trimethylsilyl chloride

the free-radical polymerization of AMAA can take place smoothly.The trimethylsilyl group can be removed easily by alcoholysis.It has been revealed by ESR analysis that the carbon atom which connected three strongly electron negative carbonyl groups in AMAA molecule forming a stable carbon free radical lead to retard the propagation during the free-radical polymerization.