Experimental and Theoretical Investigation of the Lamellar Structure of a Styrene−Butyl Methacrylate Diblock Copolymer by Fluorescence Resonance Energy Transfer, Small-Angle X-ray Scattering, and Self-Consistent-Field Simulations
Bibliographic record
Abstract
We have investigated the repeat distance and interface thickness, at 160 °C, of a poly(styrene- b -butyl methacrylate) (PS- b -PBMA) diblock copolymer of ∼180 000 molecular weight by small-angle X-ray scattering (SAXS) and fluorescence resonance energy transfer (FRET). We have found a lamellar period of 47 nm and an interface thickness of 5 nm. A simple, hyperbolic secant model of the junction distribution appeared to be sufficient to analyze the fluorescence decay data on the junction-labeled polymer containing different acceptor/donor ratios, but simulations based on a numerical self-consistent-field (NSCF) formalism also allowed us to find a range of approximately 0.017−0.018 for the Flory−Huggins interaction parameter (χ FH, defined with reference to the monomeric volume of polystyrene) and a PBMA Kuhn length ( b PBMA ) of 0.65−0.67 nm. We note that earlier values of χ FH and b PBMA reported in the literature vary considerably. The NSCF computations suggest that even modest levels of conformational asymmetry perturb the block copolymer morphology. A weakness of our theoretical (NSCF) approach is the compressible nature of PS- b -PBMA. However, lattice cluster, equation of state (EOS), or other models that allow for compressibility have not yet been developed to the level of sophistication needed to predict block copolymer repeat distances or interface thicknesses. Indeed, as detailed in the Supporting Information, current EOS methods leave much to be desired even in predicting the phase transitions of lower molecular weight PS- b -PBMA samples.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".