“Core-First” Synthesis of Multiarm Star Polyethylenes with a Hyperbranched Core and Linear Arms via Ethylene Multifunctional “Living” Polymerization with Hyperbranched Polyethylenes Encapsulating Multinuclear Covalently Tethered Pd-Diimine Catalysts
Bibliographic record
Abstract
We demonstrate in this paper the novel synthesis of multiarm star polyethylenes of well-defined arm lengths and controllable average arm numbers through the core-first multifunctional “living” polymerization protocol from ethylene stock. These novel star polymers are featured with a core−shell structure, having a hyperbranched polyethylene core joining multiple linear polyethylene arms bearing short branch structures. Utilizing the outstanding features of cationic Pd−diimine catalysts, a three-step synthesis procedure incorporating two sequential Pd−diimine catalyzed ethylene polymerization steps is employed. Hyperbranched polyethylenes bearing different numbers of pendant acryloyl groups (HPE1 and HPE2) were first synthesized with an acetonitrile Pd−diimine catalyst ( 2 ) by nonliving chain walking copolymerization of ethylene with 1,4-butanediol diacrylate at elevated concentrations. These two hyperbranched polymers having the specific acryloyl anchoring sites were used as the homogeneous support in the second step for the covalent immobilization of catalyst 2 to generate hyperbranched polyethylenes encapsulating multinuclear covalently tethered Pd−diimine catalysts (HPE-Pd-1 and HPE-Pd-2). Acting as the multifunctional initiating hyperbranched core in the third step, the two multinuclear hyperbranched Pd catalysts initiated and catalyzed successfully ethylene multifunctional “living” polymerization at 400 psi and 5 °C, and led to simultaneous multidirectional arm growth from the hyperbranched core to form two sets of star polymers of very high molecular weights (SPE1 and SPE2 sets, respectively, with number-average molecular weight M n up to 1,379 kg/mol). The arm growth catalyzed by the tethered Pd centers in the polymerization is confirmed to be “living”, with M n of both star polymers and the arms increases nearly linearly with polymerization time. Determined essentially by the average numbers of tethered acryloyl groups in HPE1 and HPE2, high average arm numbers (about 21 and 28 per star, respectively) were achieved in the star polymers, along with narrow-distributed tunable arm length (up to about 48 kg/mol). Study on dilute solution properties of these two sets of star polymers confirms their spherical chain conformation and resemblance of rigid spheres and high-generation dendrimers.
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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".