Intramolecular Complexation in Aqueous Solutions of an End-Capped Poly(Ethylene Glycol)
Bibliographic record
Abstract
1 H NMR, 2D NOESY, and spin−lattice relaxation time ( T 1 ) measurements were used to investigate the aqueous solution behavior of poly(ethylene glycol) monomethyl ether 3,5-dinitrobenzoate (PEG-DNB). A cloud point diagram revealed a phase behavior consisting of two phase separation processes, one, at high temperature, common for solutes containing oxyethylene groups whose solubility in water decreases with temperature, and the other, at low temperature, driven by the hydrophobicity of the DNB group. The intramolecular charge-transfer complexation between the ether oxygens from the PEG chains, acting as p-electron donors, and the dinitrobenzoyl group, which is a π-electron acceptor, was found to be the cause of the unusual phase behavior and 1 H NMR multiplet patterns. The molecular weight selectivity of the chemical shift was correlated to the different conformations adopted by complexes having different PEG lengths. These conformations are the result of the competition between hydration forces on one hand, and CT interactions and hydrophobicity of DNB on the other. In addition to complexation, there are large aggregates forming due to the amphiphilic character of these molecules. To explain the coexistence of aggregation and coiled complex conformation a model is proposed, consisting of supramicellar composite (multicenter) aggregates formed by the association of many PEG-DNB coils, each being unimolecular micelles. The composite aggregates are characterized by a hydrophobicity gradient associated with the molecular weight distribution along the aggregate radii.
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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".