Probing Molecular Interactions of an Asphaltene Model Compound in Organic Solvents Using a Surface Forces Apparatus (SFA)
Bibliographic record
Abstract
Studies on the molecular interaction mechanisms of asphaltenes in organic solvent have not reached a widely accepted conclusion, mainly because of a poor definition of asphaltene molecules and lack of accurate information on the molecular structure. In this study, N -(1-hexylheptyl)- N ′-(5-carboxylicpentyl) perylene-3,4,9,10-tetracarboxylic bisimide (C5Pe) of the polyaromatic core with a proper molecular weight and heteroatoms in its structure was used as a model compound of asphaltenes in an attempt to understand interaction mechanisms of molecular aggregation in organic solvents. A surface forces apparatus (SFA) was used to directly measure the molecular interactions of C5Pe in toluene and heptane. For the interactions between two model clay (mica) surfaces across a C5Pe-in-toluene solution, the repulsion observed between the adsorbed C5Pe molecules was shown to be of a steric origin. The force–distance profiles at short separation distances under high compression force during approaching were well-fitted with the Alexander–de Gennes (AdG) scaling theory, while the weaker repulsive forces at lower compression force regime over longer separation distances can also be fitted with the AdG model using an independent set of fitting parameters, indicating the presence of possible secondary brush structures of the C5Pe molecules in toluene. For interactions of pre-adsorbed C5Pe films (C5Pe versus mica and C5Pe versus C5Pe), no significant adhesion was detected in toluene, while strong adhesion was measured in heptane. The comparison of the results obtained with the model compound C5Pe and native asphaltenes shows that C5Pe behaves quantitatively different from the real asphaltenes in the context of contact angle and interaction force profiles. However, there are qualitative similarities in terms of intermolecular forces, indicating that the polar components in real asphaltene molecules play an important role in determining their interfacial activities.
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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 | 0.000 |
| 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) | 0.001 | 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".