THERMOGRAVIMETRIC STUDIES OF POLYSTYRENE OF MODIFIED COBALT 5-METHYL-5-HEXEN-2,4-DIONATE

Abstract

Thermogravimetry was used to study polystyrene samples modified with cobalt 5-methyl-5-hexene-2,4-dionate (MHD-Co) in two ways. The first method consists in copolymerizing styrene with the metal monomer MHD-Co, which simultaneously acts as an initiator and an inhibitor in this process, namely it exhibits a multifunctional effect in radical copolymerization with vinyl monomers. The polystyrene obtained in this way contains ≤ 0,5% cobalt in the form of β-diketonate groups covalently linked to the macromolecule, which are located both at the ends and in the middle of the polymer chain. Such polymers can be macroinitiators and graft side chains already at the stage of their synthesis; therefore, they have a branched structure of macrochains. The second modification method consists in the preliminary preparation of a styrene copolymer with unsaturated β-diketone followed by the complexation reaction of the obtained macroligand with a metal salt. In this case, when using the Co (III) salt, polymer chelates are formed as a result of the interaction of several polymer chains, and in the case of the Co (II) salt, two β-diketone groups inside the same macromolecule form a chelate structure. Moreover, for coordination saturation, metal complexes include solvent molecules. Thus, depending on the production method, polystyrene samples containing cobalt β-diketonate have a different structure, which affects the destruction mechanism, which will be different in each method. However, regardless of the modification method, all the studied samples have increased resistance to thermal oxidative degradation compared to the sample obtained using the traditional initiator benzoyl peroxide. The paper discusses the reasons for increasing the thermal stability of polystyrene containing an organometallic modifier.