A Look at the Thermodynamics of the Association of Amphiphilic Polyelectrolytes in Aqueous Solutions: Strengths and Limitations of Isothermal Titration Calorimetry
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Bibliographic record
Abstract
The dissolution in water of the sodium salts of poly(2-acrylamido)-2-methylpropanesulfonic acid (PAMPS), N, N -di- n -octadecyl-endcapped-poly(2-acrylamido)-2-methylpropanesulfonic acid [(C 18 ) 2 -PAMPS], cholesteryl-endcapped-poly(2-acrylamido)-2-methylpropanesulfonic acid (Chol-PAMPS), and a random copolymer of AMPS and N -dodecylmethacrylamide (PAMPS-Dod 20 ) was studied by isothermal titration calorimetry (ITC). The endcapped polymers form multimolecular aggregates in aqueous solutions. The concentration range for aggregation and the enthalpy of micellization were determined as functions of the electrolyte concentration (0.01 M < [NaCl] < 0.3 M) and temperature (288 K < T < 308 K) for solutions of (C 18 ) 2 -PAMPS. At 298 K and 0.2 M NaCl, aggregation of this amphiphilic polyelectrolyte occurs in solutions with concentrations ranging from about 1 to 14 mmol of AMPS L - 1 (0.5−2.7 g L - 1 ) with an enthalpy of micellization of ∼100 J (mol of AMPS) - 1 . The effect of the experimental conditions, such as the method of preparation of the polymer stock solution and its concentration, on the ITC results is described in the case of Chol-PAMPS. Titrations performed with poly(sodium-2-acrylamido-2-methylpropane sulfonate) (PAMPS) confirmed that PAMPS does not aggregate in aqueous NaCl, whereas PAMPS-Dod 20 forms predominantly unimolecular micelles. The advantages and limitations of ITC for studying the micellization thermodynamics of amphiphilic polyelectrolytes are discussed.
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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.
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