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

Abstract

Summary: Syndiotactic polymers of 1‐pentene, 1‐hexene and 1‐octene were obtained with the CS‐symmetric metallocene catalysts [Ph2C(Cp)(2,7‐tert‐Bu2Flu]ZrCl2 and [(4‐MePh)2C(Cp)(2,7‐tert‐Bu2Flu)]ZrCl2, which have already been proven to give high molar masses and excellent tacticities in propene polymerisation. The monomers were polymerised in bulk and in solution processes at temperatures between 0 and 60 °C using methylaluminoxane as a cocatalyst. The effects on catalyst activity as well as on polymer microstructure and molar mass were determined. Polymers with high syndiotacticities and molar masses (up to 550 000 g · mol−1 in the 1‐octene polymerisation) compared to other metallocenes were obtained. magnified image

Mono‐ and binuclear nickel catalysts for 1‐hexene polymerization

“…Intrinsic viscosity, η , was measured in toluene at room temperature using an Ubbelohde viscometer. Viscosity‐average molecular weight ( M v ) values were calculated according to the Mark–Houwink equation: where the coefficients α and K are 0.69 and 2.28 × 10 −2 ml g −1 , respectively. Gel permeation chromatography (GPC) was conducted with an Agilent 1100 instrument using tetrahydrofuran as eluent, a refractive index detector at maximum temperature of 45 °C and a column with a diameter of 0.25 mm.…”

Ethylene/4‐Methyl‐1‐pentene Copolymers by a “Constrained Geometry Catalyst”: Advances in 13C NMR Assignment

“…Such a pattern differs from that reported in the literature for the linear poly(a-olefin)s. Indeed, the signal of the side chain carbon [(CH 2 (sc)] of the atactic triad is always observed at higher field with respect to the isotactic one for all studied polymers of higher a-olefins. [28][29][30][31] Moreover, in the 4M1P homopolymer, the resonances of the isotactic and syndiotactic PPP triads are very close to each other (the difference is less than 0.1 ppm), while in all known polymers of higher a-olefins, such a difference is generally about 0.8 ppm. [28] This result is not surprising since in the 4M1P homopolymer, where the side chain is b-branched, each main chain tertiary carbon is bonded to three -CH 2 -CH-(CH 3 ) 2 moieties, so that the meso-racemic difference corresponds to the exchange of two nearly equivalent moieties, thus to nearly perfectly balanced conformational effects.…”

“…6) ppm, respectively that we previously assigned to the ''external'' and the ''internal'' methyl carbon of EPPEX pentad. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] A smaller resonance (no. 5), is also detected at 21.33 ppm.…”

Effect of Different Aluminum Alkyls on the Metallocene/Methylaluminoxane Catalyzed Polymerization of Higher α‐Olefins and Styrene

“…However, the number-average molecular weight of poly(1-heptene)s was somewhat higher: M n % 30 000 g Á mol À1 (entries 8, 9, Table 1). The reason of such increase in M n with increasing the chain length of the monomer is unclear for us now, although several authors also observed similar effects, [40,41] while others reported that M n is independent of the chain length of the monomer. [37,42] It should be also noted that molecular weights of higher poly(a-olefin)s synthesized, determined by NMR spectroscopy, were typically higher than M n s calculated from SEC data [43] (M n was calculated based only on the olefinic chain end structures, for detail see Experimental Part and Figure 3).…”