Effects of Charge Density and Counterions on the Assembly of Polyelectrolyte Multilayers
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Bibliographic record
Abstract
The kinetics of the electrostatic layer-by-layer adsorption of a weakly charged polycation, poly(allylamine hydrochloride), PAH, and a polyanion containing an azobenzene chromophore, P-Azo, was studied using UV−vis spectroscopy and ellipsometry. The thickness of the multilayer films was first measured over the adsorption pH range of 3 to 11, and the growth of multilayers was examined as function of time and concentration. Films assembled in bath pH near that of their p K a value produced both the thickest films and displayed remarkably rapid adsorption isotherms. In some PAH/P-Azo films, a significantly large thickness was achieved in less than 5 s, which is more than 2 orders of magnitude faster than what is usually observed. We show that this anomalously rapid adsorption is a consequence of the weak acid−base nature of the layers. In addition, the role of counterion displacement in multilayer formation from weakly charged polyelectrolytes was explored by examining the rates of P-Azo adsorption in PAH/P-Azo multilayer formation from polymer solutions containing the counterion series F -, Cl -, Br -, and I - . Multilayers of PAH/P-Azo prepared from solutions containing I - ions exhibited 21% greater adsorption at saturation ( t = 60 s) than those containing an equal concentration of F - ions. We provide a simple scaling rationalization relating the counterion binding energies with the observed rates of displacement by an adsorbing polymer segment.
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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