<sup>8</sup>Li Spin Relaxation as a Probe of the Modification of Molecular Dynamics by Inelastic Deformation of Glassy Polystyrene
Bibliographic record
Abstract
Abstract The molecular dynamics of inelastic strain in glasses remains poorly understood, in contrast to the plasticity of crystalline materials that is well-characterized by measurements of dislocation activity. We report initial results on a 300 nm thick atactic polystyrene film undergoing plastic strain in its glassy state. This physical modification was applied by nanoimprint stamping with a 1 mm ultra-smooth spherical die to induce a stress exceeding mechanical yield (0.8% residual strain). Using 8Li implanted-ion βNMR, we monitor the spin-lattice relaxation to infer depth-resolved rates of molecular dynamics. We find a significant change in the bulk molecular dynamics of the imprinted film (away from the surface) compared to an identically prepared control film. The relaxation is ∼ 20% slower in the film left densified by imprinting. We expect this relaxation to be coupled to the motion of the phenyl side rings; wherein slower dynamics due to densification is reasonable, as tighter packing should increase the energy barrier to molecular motion. In addition, we see an increase in the apparent thickness of a nanometric mobile surface layer, but this may be an artefact of surface roughening caused by imprinting.
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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".