Trans‐1,4‐stereospecific copolymerization of isoprene and butadiene catalyzed by TiCl4/MgCl2 Ziegler–Natta catalyst: III Effect of alkylaluminium on monomer reactivity ratios

Abstract Copolymerizations of isoprene (Ip) and butadiene (Bd) in different Bd/Ip feed ratios were carried out using the heterogeneous TiCl 4 /MgCl 2 type Ziegler–Natta (Z‐N) catalysts activated by trimethylaluminium (AlMe 3 ), triethylaluminium (AlEt 3 ), triisobutylaluminium (Al(i‐Bu) 3 ) or tri‐ n ‐octylaluminium (AlOct 3 ). Monomer reactivity ratios of Ip and Bd ( r Ip , r Bd ) in the copolymerizations were calculated by the Kelen–Tödüs method and then instantaneous compositions of the copolymers were theoretically acquired based on the Mayo–Lewis equation. The effects of alkylaluminiums on copolymerization activity, copolymer microstructure, comonomer incorporation, monomer reactivity ratios and copolymer instantaneous composition were investigated. Using AlEt 3 led to higher copolymerization activity and trans ‐1,4 stereoselectivity compared with other trialkylaluminiums. AlOct 3 with bulky n ‐octyl groups showed a higher Bd monomer reactivity ratio. The theoretical copolymer composition drift based on the Mayo–Lewis equation was in good coincidence with the experimental data measured by real‐time 1 H NMR during the steady polymerization stage. The nature of the discrepancy between the theoretical and measured copolymer compositions obtained in the initial polymerization stage is discussed in detail. © 2021 Society of Industrial Chemistry.