Study of Interaction of Poly(ethylene imine) with Sodium Dodecyl Sulfate in Aqueous Solution by Light Scattering, Conductometry, NMR, and Microcalorimetry
Bibliographic record
Abstract
Light scattering studies show that in aqueous solution poly(ethylene imine) (PEI) exists largely in the form of individual macromolecules plus a small fraction of aggregates. The aggregates make a large contribution to the scattering signal but only a very small contribution to the solution viscosity. Addition of sodium dodecyl sulfate (SDS) to the solution has a number of interesting consequences. Microcalorimetry experiments show that well below the critical micelle concentration of SDS, individual SDS molecules add to the PEI through an exothermic process. At higher SDS concentrations, there is a noncooperative adsorption, which is endothermic in nature, of SDS micelles onto the polymer chains. The surfactant−polymer complex likely contains several polymer molecules. These solutions are characterized by a higher specific conductivity than can be explained by the sum of the conductivities of all the individual ions in solution, even if the Na + and DS - ions were free in solution and not bound to the polymer. Pulsed-gradient NMR measurements were carried out to examine the Na + and DS - ion mobility in the solutions. These measurements showed that surfactant binding to the polymer released sodium ions from the SDS micelles. The increase in pH showed that this binding also releases a small amount of OH - into the solution. These two effects by themselves are not large enough to account for the measured conductivity of the solutions. We speculate that there is high ionic mobility inside the polymer−surfactant complex that adds to the overall conductivity of the solution.
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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 | 0.001 | 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 | 0.001 | 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".