ESR Study on Diffusion-Controlled Atom Transfer Radical Polymerization of Methyl Methacrylate and Ethylene Glycol Dimethacrylate
Bibliographic record
Abstract
An electron spin resonance (ESR) spectrometer was applied on-line to the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) initiated by methyl α-bromophenylacetate (MBPA) with copper bromide (CuBr) and 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) as catalyst and ligand. The Cu(II) ESR signal was observable from the very beginning of the polymerization. The methacrylate radical spectrum appeared at a later stage due to the network formation of the system that imposed diffusion limitations on the fast radical deactivation and termination reactions. The radical and Cu(II) concentrations were measured and analyzed. The polymerization process appeared to have three definable stages. In the first stage, the Cu(II) concentration increased continuously but slowly. The methacrylate radical signal was not detectable because its concentration was below the sensitivity of the ESR machine. In the second stage, the Cu(II) concentration increased dramatically. The methacrylate radical signal started to appear and increased synchronously with the Cu(II) concentration. The autoacceleration was because the radical deactivation became diffusion-controlled. In the third stage, the Cu(II) and radical concentrations increased gradually and reached a steady state due to radical trapping in the network. The observation of the radical intermediate in ATRP further supported the radical mechanisms proposed for the transition-metal-mediated polymerization. The effects of comonomer composition, catalyst and initiator concentrations, and temperature on the radical concentration profiles were examined. The gel fraction, not the monomer conversion, determined the onset of the radical accumulation in this cross-linking ATRP system.
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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".