Activation of iPr(CpFluo)ZrCl2 by methylaluminoxane, 3. Kinetic investigation of the syndiospecific hex-1-ene polymerization in hydrocarbon and chlorinated media

Abstract

SUMMARY: The homopolymerization of hex-1-ene in presence of the iPr(CpFluo)ZrCl 2 /MAO system has been investigated in solvents of various polarity and coordinating power (toluene, methylene dichloride and o-dichlorobenzene). Polymerization kinetics were monitored by dilatometry. A strong enhancement of the activity is observed in polar solvents compared to toluene. Besides, the use of polar media enables to reduce drastically the amount of methylaluminoxane (MAO) to reach the plateau of maximum activity. However, unlike the rac-Et(Ind) 2 ZrCl 2 /MAO system, a rapid deactivation of the active species is observed in the different solvents examined in the case of the iPr(CpFluo)ZrCl 2 /MAO catalyst. Moreover, in CH 2 Cl 2 , an important loss of the catalyst syndiospecificity, proportional to the monomer concentration, is observed. The possible mechanisms involved are discussed.

13C NMR Study of the Effect of Coordinating Solvents on Zirconocene-Catalyzed Propene/1-Hexene Copolymerization

“…Experimental data have clearly shown that the solvent has a strong effect on catalyst activity [7,8,13] and, in a few cases, also on catalyst stereospecificity. [6,14] NMR [15,16] and UVvis [17] spectroscopic experiments and theoretical studies [18] have accounted for it.…”

“…Lower differences between polymerization activities in o-DCB and toluene are reported in literature. [6,7] We explain such a discrepancy as being a result of the relatively low temperature (0 8C) adopted in our experiments, which could depress the catalyst activity in toluene, MES and TIPB, but does not seem to affect the catalyst activity in o-DCB. As expected, the stereoregularity of the homopolymers does not change substantially with the solvent.…”

“…b) For a better comparison, the activity has been standardized at a propene concentration in solution of 1 mol N L -1 . c) Molar fraction of isotactic pentads, calculated according to least-squares fit of the observed integrals for the four principal methyl pentads to an enantiomorphic site-control model [7]. d) 1-Hexene content, calculated from 13 C NMR spectra.…”

Syndiospecific Homopolymerisation of Higher 1‐Alkenes with Two Different Bridged [(RPh)2C(Cp)(2,7‐tert‐BuFlu)]ZrCl2 Catalysts

“…Kinetics and the influence of different solvent polarities on hexene polymerisation were analysed by Odian [12] as well as Deffieux, [13] while Yamaguchi [14] polymerised hexene under high pressures. Kolthammer [15] determined the polymerisation kinetics of 1-octene.…”

Poly(pent-1-ene) Synthesized with the Syndiospecific Catalyst i-Pr(Cp)(9-Flu)ZrCl2/MAO

“…[9][10][11][12][13] Coevoet et al investigated the kinetics of the homopolymerization of 1-hexene in the presence of 1 in solvents of various polarity and coordinating power. [14] Recently, we reported on the polymerization of higher 1-olefins ranging from 1-pentene to 1-decene using various metallocene catalysts including 1 and also discussed the properties of the synthesized poly(1-olefins). [15] In this study, the influence of the polymerization conditions on the stereoregularity of poly(pent-1-ene) synthesized with the system 1/MAO was targeted for special attention (Scheme 1).…”