Compensatory method for the synthesis of chelating polymeric ligands based on styrene and 5-methyl-5-hexene-2,4-dione as a way to increase the efficiency of macroinitiators of the b-diketonate type

Abstract

Polymeric chelating ligands based on styrene and unsaturated -diketone 5-methyl-5-hexene-2,4-dione (MHD) were prepared by radical copolymerization initiated by benzoyl peroxide in benzene solution at the volume ratios of monomers styrene:MHD=1:30 and 1:10. In this case, -diketone was added to the system by conventional (simultaneous) and compensatory (equal portions at conversions of 0, 5, and 10%) methods. The resulting products were studied by IR and 1H NMR spectroscopies. It has been shown that macrochelates obtained on the basis of such ligands differ in their structure and as a consequence in their macroinitiating ability in the grafting of vinyl monomers. Polymeric ligands synthesized at the ratio of 1:10, regardless of the preparation method, form mixed-ligand complexes in the subsequent complexation reaction with cobalt(II) acetate, which exhibit weak activity in styrene grafting and are not effective in the case of methyl methacrylate. The use of a small amount of MHD (1:30) in combination with the compensatory synthesis method leads to the predominant formation of intramolecular complexes of the -diketonate type, which are more active macroinitiators in the graft polymerization of styrene and methyl methacrylate than those obtained by the traditional simultaneous method of adding MHD.