Time-Resolved Infrared Spectroscopic Studies of Poly(ethylene terephthalate) Deformation
Bibliographic record
Abstract
Polarization modulation infrared linear dichroism (PM-IRLD) and ultrarapid-scanning Fourier transform infrared spectroscopy (URS-FTIR) have been used to characterize the evolution of molecular orientation and microstructure during and following the step deformation of amorphous poly(ethylene terephthalate) (PET) above and below its glass transition temperature. The combined use of these techniques allowed a high sensitivity and an unprecedented 10 ms time resolution for the characterization of irreversible polymer deformation using infrared spectroscopy. PM-IRLD results show that the 1410 cm -1 band of PET, often used as a thickness standard, presents a significant dichroism even at low draw ratios. Using this band, the relaxation kinetics of the phenyl ring was directly shown, for the first time, to be similar to that of the glycol group in amorphous PET. These results suggest that the relaxation proceeds mainly via cooperative motions involving at least one repeat unit and not only through rotations around the flexible CH 2 −CH 2 and CH 2 −O bonds. The real-time study of the cold drawing of glassy amorphous PET by URS-FTIR showed that a large gauche-to-trans conversion (from ∼15% to 60% of trans conformers) of the glycol groups occurs during the neck propagation. These trans conformers possess a very large and stable molecular orientation. Nevertheless, spectral analysis revealed that the “mesomorphic” phase, rather than the truly (all-trans) crystalline structure, is produced during cold drawing of PET at room temperature.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.001 | 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 teacher head, 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".