Shared Depletion and Restabilization Colloidal Interactions in Phase Diagrams for Silica Nanoparticle and Asphaltene + Polystyrene + Solvent Mixtures
Bibliographic record
Abstract
Nanocolloids (nanoparticle + solvent mixtures) and nanocolloid + non-adsorbing polymer mixtures arise in fields as diverse as pharmaceutics, hydrocarbon production, and environmental science. While there are many parallels with the phase behavior of molecular fluids, the driving forces for phase behavior, modeling approaches, and terminologies used to describe them differ markedly, reflecting historical examples and applications that underlie the development and understanding of phase diagrams in these fields. Here, for example, we link the concept of theta and non-theta solvent, in colloid phase diagrams, to upper critical end points arising in polymer + solvent binary mixtures in simple fluids by integrating concepts from both fields. We show that the phase behavior of silica nanoparticles (7 nm diameter) + polystyrene (237 kg/mol) + cyclohexane is qualitatively similar to the phase behavior of chemically separated Athabasca pentane asphaltenes and physically separated Athabasca retentate (comprising 43.1 wt % pentane asphaltenes) + atactic polystyrene (400 kg/mol) + toluene. All three mixtures exhibit two-phase regions, where one phase is enriched with polymer and the other phase is enriched with nanoparticles. The phase boundaries are reversible and include critical points, underscoring the overlap in particulate states in both phases. The experimental methods, phase boundaries, and fluid–fluid critical points are presented and discussed. X-ray transmission was found to be more robust than acoustic transmission for the identification of two-phase to one-phase boundaries and critical points for these mixtures. The outcomes of this work add to our understanding of the phase behavior of solvent + non-adsorbing polymer + nanoparticle mixtures for cases where dispersive energies are weak. More specifically, they improve our understanding of asphaltene and asphaltene-rich fluid behaviors in reservoirs and production, transport, and refining processes. We broaden the conceptual understanding of asphaltene behavior and underscore the importance of a colloidal approach for modeling asphaltene stability.
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 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".