Kinetics of Propylene Polymerization Using Bis(2-phenylindenyl)zirconium Dichloride/Methylaluminoxane
Bibliographic record
Abstract
The kinetics of propylene polymerization in toluene solution by bis(2-phenylindenyl)zirconium dichloride/methylaluminoxane at 20 °C were investigated. As the structure and properties of elastomeric polypropylenes produced by these catalysts depend sensitively on the reaction conditions, a detailed study of the kinetics was carried out to evaluate the influence of these parameters on the polymerization behavior. Studies of the solubilities and mass-transfer rates reveal that dissolved atactic polypropylene has little effect on propylene solubility but influences the mass-transfer rate of propylene into solution. The rates of propylene polymerization reach a maximum after 10−20 min and then decrease. The decrease in rate over time is faster at higher monomer concentrations. Catalyst activity was negligible at [Al]/[Zr] = 1000 but constant from [Al]/[Zr] = 2500 to [Al]/[Zr] = 10 000. Analysis of molecular weights as a function of monomer concentration reveal β-hydride elimination to be the primary chain-transfer mechanism. Narrow molecular weight distributions ( M w / M n = 2.0−2.6) were obtained. The increase of the isotactic dyads and pentads ([m] and [mmmm]) with increasing monomer concentration reveals an additional kinetic event which competes with the stereodifferentiating olefin insertion step. Modeling studies are more consistent with a mechanism involving interconversion of the catalyst between isospecific and aspecific states than a mechanism involving epimerization of the stereogenic centers of the growing polymer chain.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".