Long‐Chain Branching and Rheological Properties of Ethylene‐1‐Hexene Copolymers Synthesized from Ethylene Stock by Concurrent Tandem Catalysis
Bibliographic record
Abstract
Abstract Summary: Concurrent tandem catalysis systems have shown a significant advantage in the convenient synthesis of linear low‐density polyethylene (LLDPE) from a sole ethylene monomer stock by uniquely coupling the tandem action between an ethylene oligomerization catalyst and an ethylene copolymerization catalyst in a single reactor. Recently, we have reported the successful synthesis of ethylene‐hexene derived LLDPE using an effective concurrent tandem catalysis system comprising (η5‐C5H4CMe2C6H5)TiCl3 (1)/MMAO and a CGC copolymerization catalyst, [(η5‐C5Me4)SiMe2(tBuN)]TiCl2 (2)/MMAO. In this work, we report the results from an extensive study on the important rheological properties of LLDPE grades prepared with this tandem catalysis system. Two sets of LLDPE samples having different short‐chain branching density (SCBD) were prepared with the tandem catalysis system under various catalyst concentrations and at temperatures of 25 and 45 °C. The melt rheological properties of these polymers were evaluated using small‐amplitude dynamic oscillation measurements. These polymers have been found to possess typical rheological properties found in long‐chain branched (LCB) polymers, such as enhanced zero‐shear viscosity (η0), improved shear‐thinning, elevated dynamic moduli, and thermorheological complexity, which indicate the presence of long‐chain branching in the polymers. The long‐chain branching density (LCBD) of the two respective sets of polymers were qualitatively compared and correlated to the polymerization conditions including catalyst ratio and temperature. This work represents the first study on the rheological properties of LLDPE synthesized with concurrent tandem catalysis, and it discloses another appealing feature of this unique approach—its ability to produce LCB LLDPE from a single ethylene monomer stock. Synthesis of linear low‐density polyethylene (LLDPE) from ethylene using ethylene oligomerization catalyst and an ethylene copolymerization catalyst. magnified image Synthesis of linear low‐density polyethylene (LLDPE) from ethylene using ethylene oligomerization catalyst and an ethylene copolymerization catalyst.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".