Effect of Spacer Length on the Specificity of Counterion-Cationic Gemini Surfactant Interaction
Bibliographic record
Abstract
Aqueous solutions of three dicationic quaternary N,N-dimethylammonium gemini surfactants with identical hydrocarbon tails (N-hexadecyl) separated by flexible two, four, and six carbon atom spacers (di-, tetra-, and hexamethylene), abbreviated as G2, G4, and G6, respectively, were characterized using dynamic light scattering (DLS), Langmuir balance, differential scanning calorimetry (DSC), and microscopy in the presence of varying concentrations of sodium salts of fluoride, chloride, bromide, and iodide. Clear dependence on the counterion species was evident in the surface activity of the geminis, as follows. In 0.1 mM salt minima in surface tension and hence presumably the highest affinity for G2, G4, and G6 were observed with fluoride/chloride, bromide, and iodide, respectively. This same ion specificity of G2, G4, and G6 was evident also in the changes of average hydrodynamic diameters (Zav) with temperature. More specifically, maximum in Zav for G2 was observed in 100 mM NaCl, for G4 in 100 mM NaBr, and for G6 in 1 mM NaI. Our results demonstrate that spacer length has a profound impact on the interaction of these surfactants with halide counter-ions of different sizes, controlling the organization of these cationic geminis in the presence of salt. Importantly, our studies show that adjusting the headgroup structure it is possible to design amphiphiles, which can be used to bind specific metal ions in solution, for purposes such as water purification and mineral enrichment.
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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 | 0.001 |
| 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 | 0.000 | 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".