Ionomer Self-Assembly in Dilute Solution: A Molecular Dynamics Study
Bibliographic record
Abstract
Self-assembly of ionomer chains in dilute solution is studied by classical molecular dynamics. Based on a bead-spring ionomer model, the simulation approach captures formation of cylindrical, bundle-like [1] aggregates with a hydrophobic core region, a surface layer of charged anionic headgroups and a halo of counterions (protons) in the surrounding aqueous phase. Ionomer aggregation enforces the stretching and stiffening of ionomer chains, which is caused mainly by the repulsion of anionic headgroups. The strengths of hydrophobic and electrostatic interactions are varied to explore their effect on the aggregation process. Strong hydrophobicity of the ionomer main chain results in greater aggregate sizes. Figure 1a shows the result of the changes in the aggregate size, , over the range of explored hydrophobicity. Strong electrostatic interaction of ionic headgroups decreases the aggregate size, results are shown in figure 1b. Simulations also show the spontaneous formation of networks of ionomer bundles. Results of simulations will be discussed in the context of experimental studies on the formation of rodlike structures in ionomer solutions [2-3] that form the mechanically stable skeleton of polymer electrolyte membranes such as Nafion [4]. Moreover, implications of simulation results for water sorption phenomena [5], proton conductivity [6], membrane degradation [7] and membrane failure will be discussed. Figure caption: Figure 1. Changes of the average aggregate size, , as a function of variation in strengths of hydrophobic interactions (a) and electrostatic interactions (b). Strength of hydrophobic interactions are controlled through variation of strength of excluded volume interaction of hydrophobic monomeric beads while the electrostatic strength is varied through changes in the Bjerrum length. References: P.-É. Alix Melchy, M. H. Eikerling, Phys. Rev. E, 89, 032603, (2014). B. Loppinet, G. Gebel, C. E. Williams, J. Phys. Chem. B, 101, 1884-1892, (1997) S. Jiang, K. - Q. Xia, G. Xu, Macromolecules, 34, 7783-7788, (2001). L. Rubatat, A. L. Rollet, G. Gebel, O. Diat, Macromolecules, 35, 4050-4055, (2002). M. Eikerling, P. Berg, Soft Matter, 7, 5976–5990, (2011). K. - D. Kreuer, Chem. Mater., 8, 610–641, (1996). M. Ghelichi, P.-É. Alix Melchy, M. H. Eikerling, J. Phys. Chem. B, 118, 11375−11386, (2014) Figure 1
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 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".