Organocobalt chelates as initiators of emulsion polymerization of styrene

Abstract

The kinetics of decomposition of organocobalt chelates in the pH range of 2.2–7.0 has been studied. It has been shown that the rate constant of decomposition of the octyl chelate complex at 20°C changes from ∼3 × 10−3 to ∼6 × 10−6 s−1 in the above pH range. The rate constants of decomposition of complexes with ethyl, octyl, and cetyl ligands, as estimated at 20°C and pH 8.3, are 1.69 × 10−4, 1.39 × 10−4, and 2.42 × 10−5 s−1, respectively. As evidenced by emission spectrometry measurements, ∼100% of organocobalt chelates with ethyl and isopropyl ligands occur in the aqueous phase, while organocobalt chelates with octyl and cetyl ligands are partitioned between monomer and aqueous phases. The rates of initiation of the emulsion polymerization of styrene have been measured by the inhibited polymerization procedure. It has been demonstrated that among three tested compounds (diphenyl picryl hydrazyl, hydroquinone, and benzoquinone), benzoquinone has been found to be a suitable inhibitor for the polymerization under study. The rates of initiation of styrene polymerization at 30°C for organocobalts with ethyl, octyl, and cyclohexyl ligands are 1.0 × 10−7, 1.04 × 10−7, and 3.7 × 10−6 mol/(l s), respectively. The rate constant of decomposition of the organocobalt complex with the octyl ligand at 30°C is 2.28 × 10−5 s−1, and the efficiency of initiation with this complex is 0.95.