| name | polymer-films |
| description | Domain knowledge for polymer thin film reflectometry analysis. Covers common polymer SLD values, isotope labeling conventions, typical film thickness ranges, and contrast matching strategies. Use when the sample involves polymers, polystyrene, polymer brushes, block copolymers, or spin-coated films.
|
| metadata | {"author":"aure","version":"1.0"} |
Common Polymer SLDs (×10⁻⁶ Å⁻²)
| Material | SLD |
|---|
| Polystyrene (h-PS) | 1.4 |
| d-Polystyrene (d-PS) | 6.4 |
| PMMA (h-PMMA) | 1.06 |
| d-PMMA | 7.1 |
| Polyethylene (h-PE) | -0.3 |
| d-Polyethylene (d-PE) | 7.0 |
| Polyisoprene (h-PI) | 0.27 |
| d-Polyisoprene (d-PI) | 6.7 |
Isotope Labeling
- Deuterium labeling replaces H with D to increase SLD contrast.
- A "d-" prefix indicates full deuteration; partial deuteration gives
intermediate SLD values.
- When the sample mentions both h- and d- versions, the SLD difference
provides the contrast mechanism.
- Be careful not to confuse protonated and deuterated variants — check
if the description specifies the isotope labeling.
Typical Thickness Ranges
| Film Type | Typical Thickness |
|---|
| Spin-coated thin film | 100–2000 Å |
| Polymer brush (grafted) | 50–500 Å |
| Block copolymer lamellae | 100–500 Å per domain |
| Adsorbed polymer layer | 10–100 Å |
| Self-assembled monolayer | 10–30 Å |
Contrast Matching Strategies
- Matching the SLD of one component to the solvent makes that component
"invisible," revealing the other component's structure.
- Common contrast match points:
- h-PS in d-toluene: PS becomes nearly invisible
- d-PS in h-toluene: solvent SLD ≈ 0.94, d-PS stands out
- Polymer in D₂O/H₂O mixture: tune to match specific component
Swelling and Solvent Penetration
- Polymer films may swell in solvent, changing thickness and SLD.
- The SLD of a swollen layer is a volume-weighted average of polymer and solvent SLDs.
- If fitting a swollen film, allow wider SLD and thickness bounds than the dry film values.
Refinement Strategy — Polymer Films
When refining polymer thin film models:
- Thickness drift: Polymer film thickness can vary from nominal due to
processing conditions. Allow thickness bounds of ±50% around the nominal
value for spin-coated films.
- SLD between isotope variants: If the fitted SLD falls between h- and d-
values (e.g., 3.9 for PS where h-PS = 1.4 and d-PS = 6.4), this suggests
partial deuteration or isotope blending. Adjust bounds to the appropriate
intermediate range rather than forcing a pure-isotope SLD.
- Brush/grafted layers: These often have graded density profiles. If χ²
is high and roughness is large relative to thickness, consider whether
the single-slab approximation is adequate before adding sublayers.
- Swollen films: When the sample is measured in solvent, the layer SLD
should be allowed to vary between the dry polymer SLD and the solvent SLD.
Set SLD bounds accordingly.
