Influence of the catalyst on monomer insertion in the syndiospecific copolymerization of styrene and para‐methylstyrene

Abstract

The effect of the kind of transition-metal catalyst on the extent of comonomer insertion in the syndiospecific complex-coordinative copolymerization of styrene and para-methylstyrene has been investigated. The results for the influence of the polymerization conditions have shown that there is no real difference between solution copolymerization in toluene and solvent-free styrene copolymerization in bulk, with respect to the reactivity ratio for para-methylstyrene (r 2 ), under comparable conditions in the presence of methylaluminoxane and triisobutylaluminum and at low polymerization conversions. All the investigated catalysts lead to a preferred incorporation of para-methylstyrene into the polymer chain in comparison with styrene and over the whole range of monomer compositions. The increasing capability of the different catalysts to provide copolymers with enhanced para-methylstyrene concentrations can be summarized by the increasing r 2 values for the copolymerization in bulk as follows: 5 -pentamethylcyclopentadienyl titanium trichloride Ͻ 5 -octahydrofluorenyl titanium trimethoxide Ͻ 5 -octahydrofluorenyl titanium tristrifluoroacetate Ͻ 5 -cyclopentadienyl titanium(N,N-dicyclohexylamido)dichloride Ͻ 5 -cyclopentadienyl titanium trichloride. For a correlation between the catalyst structure and the comonomer insertion, the catalysts can be described by electronic effects (electrostatic charge of the transition-metal atom) and steric effects (minimum structural cone angle). The results show that the steric properties of the transition-metal complexes have the most important effect on the insertion of para-methylstyrene into the copolymer. If the minimum structural cone angle of the ligand of the transition-metal catalyst decreases, the incorporation of the comonomer para-methylstyrene increases significantly.

The Influence of t-Butyl and Cyclododecyl Substitution on Ethylene/1-Hexene Copolymerization Using Ansa-Fluorenylamidodimethyltitanium Derivatives

“…Superior to conventional Zeigler-Natta and metallocene catalysts, CGCs are capable of improving products in terms of much higher comonomer incorporation, narrower comonomer and molecular weight distribution which leads to better mechanical and physical properties. However, the incorporation of α-olefins that would result in the polymer properties depends on the structure of catalyst employed during copolymerization [ 1 , 6 , 7 ]. In fact, small variations of the ligand structure or ligand substituents may cause profound changes in the catalytic activity, copolymerization behavior and properties of the resulting polymer [ 3 , 4 , 5 , 8 ].…”