The syndiospecific polymerization of styrene in the presence of fluorine‐containing half‐sandwich metallocenes

Schellenberg, Jürgen

doi:10.1002/1099-0518(20000701)38:13<2428::aid-pola150>3.0.co;2-#

Cited by 21 publications

(5 citation statements)

References 16 publications

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“…A recent review covers syndiospecific styrene polymerization, especially the catalytic systems 3. Studies in this field have led to the conclusion that half‐sandwich titanium chloride, fluoride, or alkyoxide compounds containing η 5 ‐C 5 H 5 , η 5 ‐C 5 Me 5 , η 5 ‐C 5 Me 4 H, or η 5 ‐C 9 H 7 ligands are among the favored precursors 4–13. Kinetic studies of syndiospecific styrene polymerization with various metallocene catalyst systems have been reported by several research groups 14–21.…”

Section: Introductionmentioning

confidence: 99%

Syndiospecific styrene polymerization with CpTiCl₃/MAO: Effects of the order of reactant addition on polymerization and polymer properties

Huang

Cao

et al. 2004

J of Applied Polymer Sci

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Syndiospecific styrene (St) polymerization, catalyzed by the CpTiCl 3 /methylaluminoxane (MAO) system, was investigated using two different activation procedures. The polymerization parameters included polymerization time, temperature (ϳ25-100°C), ratio of [Al]/[Ti] (ϳ100 -1000), and catalyst precursor concentration (ϳ0.5-10.0 ϫ 10 Ϫ4 mol Ti/L). It was found that adding reactants in the order of (CpTiCl 3 ϩ MAO) ϩ St (Injection of Styrene mode) gave much higher monomer conversion rates, higher weight-average molecular weights, and narrower molecular weight distributions than for the (St ϩ MAO) ϩ CpTiCl 3 (Injection of Catalyst mode). The former also yielded significantly higher syndiotacticity fractions. Differential scanning calorimetry measurements showed multiple peaks exhibiting polymorphism in crystalline syndiotactic polystyrene samples.

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Section: Introductionmentioning

confidence: 99%

Syndiospecific styrene polymerization with CpTiCl₃/MAO: Effects of the order of reactant addition on polymerization and polymer properties

Huang

Cao

et al. 2004

J of Applied Polymer Sci

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“…CpTiCl 3 (Aldrich), Cp*TiCl 3 (Crompton), and η 5 ‐cyclopentadienyl titanium( N , N ‐dicyclohexylam ido)dichloride (Cy 2 NTiCpCl 2 ; University of Oldenburg) were used as received. η 5 ‐Octahydrofluorenyl titanium trimethoxide {[656]Ti(OMe) 3 } andη 5 ‐octahydrofluorenyl titanium tristrifluoroacetate {[656]Ti(OCOCF 3 ) 3 } were synthesized according to the literature 14…”

Section: Methodsmentioning

confidence: 99%

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

Schellenberg

2005

J. Polym. Sci. A Polym. Chem.

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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.

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“…η 5 ‐1,2,3,4,5,6,7,8‐Octahydrofluorenyl titanium trimethoxide ([656]Ti(OMe) 3 ), η 5 ‐1,2,3,4,5,6,7,8‐Octahydrofluorenyl titanium tristrifluoroacetate ([656]Ti(OCOCF 3 ) 3 ) and the oxygen bridged η 5 ‐1,2,3,4,5‐pentamethylcyclopentadienyl titanium bis(trifluoroacetate) dimer [Cp*Ti(OCOCF 3 ) ( µ ‐OCOCF 3 )] 2 ( µ ‐O) were synthesized according to the literature,18,19 η 5 ‐1,2,3,4,5,6,7,8‐octahydrofluorenyl titanium ( N , N ‐dicyclohexylamido) dimethoxide ([656](Cy 2 N)Ti(OMe) 2 ), η 5 ‐cyclopentadienyl titanium ( N , N ‐dicyclohexylamido) dichloride (Cy 2 NTiCpCl 2 ) and ( N , N ‐dicyclohexylamido) titanium trimethoxide (Cy 2 NTi(OMe) 3 ) were supplied by the University of Oldenburg, and η 5 ‐1,2,3,4,5‐pentamethylcyclopentadienyl titanium trichloride (Cp*TiCl 3 ) and η 5 ‐cyclopentadienyl titanium trichloride (CpTiCl 3 ) were available from Crompton Corporation and from Aldrich Chemical Company and were used without further purification.…”

Section: Experimental Partmentioning

confidence: 99%

Melting Properties of Syndiotactic Polystyrenes and Effect of Hydrogen on Molecular Weight Distribution

Schellenberg

2005

Macro Materials & Eng

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Summary: The melting properties of syndiotactic polystyrenes are significantly affected by the structural molecular properties of the polymers. The most important influences on the melting behavior are stereoregularity, molecular weight and molecular weight distribution of the polymers. The melting temperature is increased by an enhanced syndiotacticity at sufficiently high molecular weights and at narrow molecular weight distributions. The degree of syndiotacticity obtained primarily depends on the kind and structure of the cyclopentadienyl ligand of the transition metal catalyst, whereas the effect of the other ancillary ligands on stereoregularity is negligible at the same cyclopentadienyl ligand. At narrow molecular weight distributions with $\overline M _{\rm w} /\overline M _{\rm n}$ below 2.8 and at constant stereoregularities, the molecular weight has a remarkable effect on the melting behavior at weight‐average molecular weights lower than about 80 000 g · mol−1, resulting in a significant decrease of the melting temperature until below 230 °C. The presence of hydrogen during polymerization leads to a significant shift to lower molecular weights at comparably small amounts of hydrogen, but results in the occurrence of an additional peak in the molecular weight distribution at larger hydrogen concentrations giving evidence for the formation of a second active polymerization site producing lower molecular weight polymers. At constant stereoregularity, the broadening of the molecular weight distribution leads to decreased melting temperatures and to improved flow properties of the syndiotactic polystyrenes with increasing shear rates at moderate molecular weight distributions.

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The syndiospecific polymerization of styrene in the presence of fluorine‐containing half‐sandwich metallocenes

Cited by 21 publications

References 16 publications

Syndiospecific styrene polymerization with CpTiCl₃/MAO: Effects of the order of reactant addition on polymerization and polymer properties

Syndiospecific styrene polymerization with CpTiCl₃/MAO: Effects of the order of reactant addition on polymerization and polymer properties

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

Melting Properties of Syndiotactic Polystyrenes and Effect of Hydrogen on Molecular Weight Distribution

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The syndiospecific polymerization of styrene in the presence of fluorine‐containing half‐sandwich metallocenes

Cited by 21 publications

References 16 publications

Syndiospecific styrene polymerization with CpTiCl3/MAO: Effects of the order of reactant addition on polymerization and polymer properties

Syndiospecific styrene polymerization with CpTiCl3/MAO: Effects of the order of reactant addition on polymerization and polymer properties

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

Melting Properties of Syndiotactic Polystyrenes and Effect of Hydrogen on Molecular Weight Distribution

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Syndiospecific styrene polymerization with CpTiCl₃/MAO: Effects of the order of reactant addition on polymerization and polymer properties

Syndiospecific styrene polymerization with CpTiCl₃/MAO: Effects of the order of reactant addition on polymerization and polymer properties