Halogenated poly(isobutylene-co-isoprene): influence of halogen leaving-group and polymer microstructure on chemical reactivity
Bibliographic record
Abstract
Brominated (BIIR) and chlorinated (CIIR) poly(isobutylene-co-isoprene) are commercially available materials commonly known as halobutyl rubbers. The effect of leaving-group ability on the reactivity of halogenated poly(isobutylene-co-isoprene) was studied to place iodobutyl rubber reactivity into context with these materials. The effect of microstructure on reactivity of existing commercial materials was studied through comparison to that of polymers containing rearranged halomethyl (r-CIIR, r-BIIR, and r-IIIR) microstructure (prepared from as-received BIIR). The effect of leaving group on both thermal stability and reactivity towards nucleophilic substitution with acetate, N-butylimidazole, and sulfur was examined. The material containing the iodomethyl microstructure (r-IIIR) readily underwent nucleophilic substitution at low temperatures; however, it was extremely sensitive towards dehydrohalogenation at temperatures above 65 °C. At temperatures between 100 and 135 °C, the material containing the bromomethyl microstructure (r-BIIR) demonstrated the greatest balance between reactivity toward nucleophilic substitution and elimination through dehydrohalogenation. Exceptional thermal stability at temperatures up to 190 °C was displayed by the material containing the chloromethyl microstructure (r-CIIR); however, its reactivity towards nucleophiles was variable and nucleophile dependent. Sulfur vulcanization studies showed a clear effect of microstructure on the ability to cure with sulfur. While commercial chlorobutyl rubber has no ability to cure with sulfur alone, when rearranged to its chloromethyl microstructure (r-CIIR), curing occurs readily. Both commercial (BIIR) and rearranged (r-BIIR) bromobutyl rubber readily vulcanize in the presence of sulfur; however, BIIR cures to a greater extent.
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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".