THERMODYNAMIC STUDIES OF BIS(QUATERNARYAMMONIUM) AND (N-ALKYL-) IONIC SURFACTANTS
Bibliographic record
Abstract
Thermodynamic properties and aggregation behaviour of n-alkyl m-3-m (where m = 8, 12, 16 carbon atom chains) and cyclododecyl c12-s-c12 (where s = 3,4,6) gemini surfactants containing dimethylammonium bromide head groups have been studied. The synthesized surfactants have been characterized according to their cmc, a, and surface coverage at the air-water interface. The cmc is found to decrease with increasing chain tail length in the m-3-m salt series. The cmc and counterion association to the micelle reaches a maximum value in the c12-s-c12 surfactant series for a butyl head group spacer, whereas the area per head group was observed to increase as the linker spacer length increased. Experimental apparent molar vol urnes of the binary aqueous surfactant systems were measured in the post-micelle region and an additivity scheme was used to estimate the infinite dilution apparent molar volumes. These data provided estimates of the volumes of micellization for these salts. The micellization volumes of the c12-s-c12 surfactant series are typically small, indicating no micelles or very small micelles are produced by these surfactants in aqueous medium. Mean aggregation numbers, Ns, obtained from time resolved fluorescence quenching (TRFQ) show that N, increases with increasing chain length for the m-3-m gemini surfactants. In contrast, low mean aggregation numbers were obtained for the c12-s-c12 salt series. Distribution coefficients, Kd, of mixed micelle systems consisting of sodium alkylcarboxylate salts, CnNa (where n = 10, 12), alkyltrimethyl- ammonium bromide salts. RNMe3Br (where R = 10, 12), and ethoxylated alcohols, C EO (where EO = ethylene oxide and n = 0, 1,3) were studied using 4 n an runr T} relaxation method. Results were compared against a thermodynamic method for determining Kd and found to be in agreement with this data. The presence of EO groups on the alcohol favors its solubility in anionic micelles, indicating that the interaction between the anionic micelle and the alcohol involves the EO groups of the alcohol. For the cationic systems, an increase in the number of EO groups has no effect on K, implying that the EO groups do not contribute to the interactions occurring in mixed micelles of cationic surfactants and alcohol's containing EO groups.
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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) | 0.000 | 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".