Electrokinetic Measurements Reveal Interfacial Charge at Polymer Films Caused by Simple Electrolyte Ions
Bibliographic record
Abstract
The interfacial charge on spin-coated films of poly(tetrafluoroethylene- co -2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole) (Teflon AF) was studied by streaming potential and streaming current measurements in diluted aqueous solutions of potassium chloride, potassium hydroxide, and hydrochloric acid. ζ potential and surface conductivity were derived from electrokinetic data determined at varied concentrations of the electrolytes by means of the novel microslit electrokinetic setup (ref 1: J. Colloid Interface Sci. 1998, 208, 329). The results obtained revealed the high relevance of unsymmetrical (preferential) adsorption of ions as the origin of charge formation at unpolar polymer materials in aqueous environments. The preferential adsorption of hydroxide ions (OH - ) was found to predominate as compared to the adsorption of hydronium ions (H 3 O + ) at similar concentrations, i.e., in solutions of neutral pH. No effect of preferential adsorption was induced by chloride (Cl - ) and potassium (K + ) ions. For the first time ζ potential and surface conductivity data were evaluated to quantify the charge density of the inner layer at the polymer−water interface. The results indicate the presence of both cations and anions in the stagnant layer in all analyzed cases. The charge density and the total ion concentration in this inner part of the electrical double layer were found to increase with increasing ionic strength of the solution. However, the total ion densities of the stagnant layer remained rather low. This suggests that the ions are localized in one interfacial plane. With regard to the origin of the characterized charging process we conclude that the OH - and H 3 O + ions capability to form hydrogen bonds and the difference in the structures of the hydration shells of these two ions are of highest importance to explain the observed phenomena.
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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) | 0.001 | 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 | 0.001 | 0.001 |
| 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".