Homo- and co-polymerization of polar and non-polar olefinic monomers using bicenter cobalt-diimine catalysts

Bicenter (BCn) cobalt-bis(imine) catalysts were synthesized, used to polymerize methyl methacrylate (MMA), and ۱-hexene. The effect of catalyst structure, bridging ligand, and polymerization reaction conditions were investigated. Synthesis of primary ligand of (۲,۶-dibenzhydryl-۴-ethoxyphenyl)-N=(CH۳)-C(CH۳)=O is prepared. Following to that, the final ligands of BC۱ and BC۲ bicenter catalysts were prepared via reacting the primary ligand with ۲,۳,۵,۶-tetramethylbenzene-۱,۴-diamine and ۴,۴-methylenedianiline bridges, respectively. The BC۱ catalyst demonstrated higher activity than the BC۲ catalyst. The highest activity for the BC۱ catalyst was obtained when the co-catalyst to catalyst molar ratio was [Al]/[Co]=۱۵۰۰:۱, and the polymerization temperature was ۴۰ °C. In comparison the BC۲ catalyst demonstrated the highest activity in [Al]/[Co]=۵۰۰:۱ ratio, polymerization temperature of ۷۰ °Cand showed higher thermal stability. ۱HNMR analysis revealed that the highest branching density for poly(methyl methacrylates) (PMMA) produced by BC۱ and BC۲ catalysts was ۲۲۲ and ۲۴۹ branches per ۱۰۰۰ carbon atoms, respectively. PMMA synthesized with BC۲ catalysts had the highest syndiotacticity (۵۹%). The polymer produced with bicenter catalyst (BC۱) had a relatively broad molecular weight distribution (۲.۹), according to GPC analysis. The synthesized catalysts demonstrated appropriate activity for the polymerization of MMA, but only moderate activity for ۱-hexene monomer

Keywords:

catalytic polymerization , cobalt catalyst , bicenter catalyst , α-diimine , poly(methyl methacrylate)