In situ determination of mechanism in ansa-zirconocene catalyzed polymerization of 1-decene to prepare high viscosity index poly-alpha-olefin

The high viscosity index poly-alpha-olefin was prepared by 1-decene polymerization under [EBIZrCl 2 /Al( i Bu) 3 /[Ph 3 C] + [B(C 6 F 5 ) 4 ] - system (EBI = rac-C 2 H 4 (1-Ind) 2 ), and its mechanism was investigated by in situ UV–Vis, 1 H NMR and ESI-MS. The results show that the kinematic viscosity at 100 °C (KV 100 ), viscosity index (VI) and yield of product reach to 336.3 cSt, 268 and 90.76 % under optimum reaction condition, wherein Zr/1-decene content, Al/Zr content, B/Zr content, reaction temperature and time are 10 −4 , 200, 2, 90 °C and 120 min, respectively. Meanwhile, temperature plays a crucial role in controlling the KV 100 and VI of product, with impact index of 55.43 % and 44.32 %, respectively. In situ UV–Vis, 1 H NMR, and ESI-MS analyses confirm the simultaneous generation of active (EBIZr-σ-polydecenyl cations) and inactive species (EBIZr-η 3 -(1-propyl-C 7 H 8 ) + ). The active and inactive species are generated through posing complexation to the terminal allyl of 1-decene and H 2 loss of EBIZr(u- i Bu) + , respectively. The second inactivate species (EBIZr-η 3 -(x-propyl-(3-x)-polydecenyl-C 3 H 3 ) + (x = 1 or 2)) can be activated by seizing isobutyl group in Al( i Bu) 3 . Subsequently, the polymer with an Al-capped saturated chain end is formed through chain migration. The polymerization process follows the reaction pathway: [1-decene]+[catalyst]→[active species]+[inactive species]. This is supported by the fact that all fitting curve of conversion versus time, 1-decene consumption and polymer generation conform to the Boltzmann (R 2  = 0.999). Based on those findings, a possible mechanism in ansa-zirconocene catalyzed polymerization of 1-decene is proposed.