Pseudoperiodic “Living” and/or Controlled Cationic Ring-Opening Copolymerization of Oxetane with Tetrahydropyran: Microstructure of Polymers vs Kinetics of Chain Growth
Bibliographic record
Abstract
The “living” and/or controlled cationic ring-opening bulk copolymerization of oxetane (Ox) with tetrahydropyran (THP) (cyclic ether with no homopolymerizability) at 35 °C was examined using ethoxymethyl-1-oxoniacyclohexane hexafluoroantimonate (EMOA) and (BF 3 ·CH 3 OH) THP as fast and slow initiator, respectively, yielding living and nonliving polymers with pseudoperiodic sequences (i.e., each pentamethylene oxide fragment inserted into the polymer is flanked by two trimethylene oxide fragments). Good control over number-average molecular weight ( M n up to 150 000 g mol −1 ) with molecular weight distribution (MWD ∼ 1.4−1.5) broader than predicted by the Poison distribution (MWDs > 1 + 1/DP n ) was attained using EMOA as initiating system, i.e., C 2 H 5 OCH 2 Cl with 1.1 equiv of AgSbF 6 as a stable catalyst and 1.1 equiv of 2,6-di- tert -butylpyridine used as a non-nucleophilic proton trap. With (BF 3 ·CH 3 OH) THP, a drift of the linear dependence M n(GPC) vs M n(theory) to lower molecular weight was observed together with the production of cyclic oligomers, ∼3−5% of the Ox consumed in THP against ∼30% in dichloromethane. Structural and kinetics studies highlighted a mechanism of chains growth where the rate of mutual conversion between “strain ACE species” (chain terminated by a tertiary 1-oxoniacyclobutane ion, A1) and “strain-free ACE species” (chain terminated by a tertiary 1-oxoniacyclohexane ion, T1) depends on the rate at which Ox converts the stable species T1 (kind of “dormant” species) into a living “propagating” center A1 (i.e., k a app [Ox]). The role of the THP solvent associated with the suspension of irreversible and reversible transfer reactions to polymer, when the polymerization is initiated with EMOA, was predicted by our kinetic considerations. The activation−deactivation pseudoequilibrium coefficient ( Q t ) was then calculated in a pure theoretical basis. From the measured apparent rate constant of Ox ( k Ox app ) and THP ( k THP app = k a(endo) app ) consumption, Q t and reactivity ratio ( k p / k d, k a(endo) / k a(exo), and k s / k a(endo) ) were calculated, which then allow the determination of the transition rate constant of elementary step reactions that governs the increase of M n with conversion.
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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 | 0.000 |
| 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) | 0.000 | 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".