Propagation Rate Coefficient for Radical Polymerization of<i>N</i>-Vinyl Pyrrolidone in Aqueous Solution Obtained by PLP−SEC
Bibliographic record
Abstract
Propagation rate coefficients, k p, of N -vinyl pyrrolidone (NVP) radical polymerization in aqueous solution have been measured via the pulsed-laser polymerization - size exclusion chromatography method (PLP−SEC) over an extended concentration range from 1.8 to 100 wt % NVP at temperatures between 2 and 60 °C. The SEC analyses have been carried out by a modified procedure using dimethyl acetamide as the eluent. An about 20-fold increase of k p is observed in passing from NVP bulk polymerization to reaction in dilute aqueous solution. As with nonionized methacrylic acid (MAA), for which a similarly strong change in k p has recently been reported, the large solvent effect in NVP polymerization is assigned to intermolecular interactions resulting in a significant hindrance of internal rotational motion in the transition state structure for propagation. Some contribution from a minor change in activation energy may however not be ruled out. PLP−SEC studies carried out on aqueous NVP solutions to which either polyNVP or N -ethyl-2-pyrrolidone (NEP), the saturated analogue of NVP, have been added, demonstrate that k p depends on the molecular environment at the reactive site, which is affected by NVP (or NEP) content, but not by the polyNVP content. The lowering of monomer concentration during NVP polymerization to higher degrees of monomer conversion results in an increase of k p . Variation of p H in the range 3 to 10 does not affect k p .
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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) | 0.002 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| 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".