Complex Micellization Behavior of the Polysorbates Tween 20 and Tween 80
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Bibliographic record
Abstract
Polysorbates (PSs, Tweens) are widely used surfactant products consisting of a sorbitan ring connecting up to four ethylene oxide (EO) chains of variable lengths, one or more of which are esterified with fatty acids of variable lengths and saturation degrees. Pharmaceutical applications include the stabilization of biologicals in solutions and the solubilization of poorly water soluble, active ingredients. This study characterizes the complex association behavior of compendial PSs PS20 and PS80, which is fundamentally different from that of single-component surfactants. To this end, a series of demicellization experiments of isothermal titration calorimetry with different PS concentrations are evaluated. Their experiment-dependent heats of titration are converted into a common function of the state of a sample, the micellar enthalpy Qm(c). These functions demonstrate that initial micelles are already present at the lowest concentrations investigated, 2 μM for PS20 and 10 μM for PS80. Initial micelles consist primarily of the surfactant species with the lowest individual critical micelle concentration (cmc). With increasing concentration, the other PS species gradually enter these micelles in the sequence of increasing individual cmc’s and hydrophilic–lipophilic balance. Concentration ranges with pronounced slopes of Qm(c) can be tentatively assigned to the uptake of the major components of the PS products. Micellization and the variation of the micelle properties progress up to at least 10 mM PS. That means the published cmc values or ranges of PS20 and PS80 may be related to certain, major components being incorporated into and forming specific micelles but must not be interpreted in terms of an absence of micelles below and constant properties, e.g., the surface activity, of the micelles above these ranges. The micellization enthalpy curves differ quite substantially between PS20 and PS80 and, in a subtler fashion, between individual quality grades such as high purity, pure lauric acid/pure oleic acid, super-refined, and China grade.
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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) | 0.000 | 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) | 0.000 | 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 it