Thermal Behaviour of Nafion Thin Films
Bibliographic record
Abstract
Sub-micron Nafion films are relevant to several electrochemical devices including polymer electrolyte fuel cells, sensors and actuators. Such thin films are invariably fabricated from dispersion of the ionomer in suitable solvent, e.g. by drop-casting, spin-coating or self-assembly. Often a thermal treatment or annealing step is applied to improve the mechanical properties of the film and relax the polymers. Thus, understanding the response of the ionomer thin film subjected to thermal changes is important. Furthermore, thermal characteristics of the ionomer such as glass transition temperature and thermal expansion coefficient can provide fundamental insight into structure and the nature of the interaction with the substrate. We have initiated an in-situ thermal ellipsometry and thermal FTIR study to probe the response of 20-650 nm thick Nafion thin films supported on SiO2 substrate. Ellipsometry experiments yield the thickness change as a function of temperature. This set of data yields thermal expansion coefficient of the Nafion films. The change in slope of the thickness change with temperature provides information on the nature of phase transition – glassy to rubbery or disorder-to-order. The thermal FTIR is being used as a complimentary technique to probe whether the phase change phenomenon manifests as a dramatic change in response in one of the characteristic peaks. The results obtained so far indicate that the thermal expansion coefficient of Nafion films 60 nm and lower thickness is changes with thickness but those of the films above 60 nm thickness converges to that of the bulk material. No distinct transition in slope of thickness change is observed. That is, no glass transition like behavior is observed. No thickness-dependent response in FTIR peak is observed. A sharp change in the 638-626 cm-1 doublet region is observed at temperature corresponding to the so-called a transition for Nafion. To the best of our knowledge, there have been no prior studies on in-situ thermal ellipsometry or in-situ thermal FTIR of Nafion thin films.
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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) | 0.002 | 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".