Effect of Reaction Conditions on the Kinetics of Living Isobutylene Polymerization at High Initiator/TiCl<sub>4</sub> Ratios
Bibliographic record
Abstract
The kinetics of isobutylene (IB) polymerization initiated by the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl 4 in methylcyclohexane (MeCHx)/methyl chloride (MeCl) or hexane (Hx)/MeCl 60/40 v/v at −80 °C were investigated in the range of [TMPCl] 0 /[TiCl 4 ] 0 > 1 using a real-time fiber-optic mid-IR monitoring technique. The rate of IB consumption was monitored by following the disappearance of the 1655 cm -1 IR band, characteristic of the C C stretching vibration. Both the area and the height of the 1655 cm -1 band were found to be directly proportional to IB concentration under the conditions investigated. From polymerization rate data the overall rate constant k p ‘ = k p K eq was calculated, where k p is the rate constant of propagation and K eq = k 1 / k - 1 is the equilibrium constant for the dormant/active equilibrium characteristic of living IB polymerization. The investigation revealed that k p ‘ was very sensitive to solvent quality. k p ‘ ≈ 0.5−1.7 L 2 mol -2 s -1 was found using MeCHx, while k p ‘≈ 1.7−3.4 L 2 mol -2 s -1 was obtained using Hx from different providers and/or with and without further purification. GC analysis and real-time IR monitoring revealed the presence of carbonyl contaminants in the solvents, which were found to form a complex with TiCl 4 . Regardless of solvent quality, the reaction order in TiCl 4 was found to be invariably 1 under the conditions investigated. Monomer concentration and temperature were found to have a profound effect on the polymerization; k p ‘ increased exponentially with an increase of [IB] 0 or a decrease in temperature. The apparent activation enthalpy of propagation was found to be Δ H a = −26.4 kJ/mol.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".