Study of the Microcrystallization of Ethylene−Propylene Random Copolymers in Solution by Fluorescence
Bibliographic record
Abstract
The results of fluorescence experiments carried out on two ethylene−propylene copolymers (EP) labeled with pyrene, naphthalene, or both provide the first experimental evidence of intrachain formation of crystalline microdomains in solution. Differential scanning calorimetry (DSC) experiments performed on 50 g/L EP solutions in toluene demonstrated that one EP copolymer was crystalline (EP-CR) while the other was amorphous (EP-NCR). The intrinsic viscosity of EP-CR and EP-ΝCR in toluene was measured as a function of temperature. EP-CR was the only sample to exhibit a decrease in intrinsic viscosity around 0 °C, suggesting a decrease of the hydrodynamic volume of the polymer coil as expected if EP-CR forms microcrystals in solution. The light scattering intensity of 2 g/L solutions of EP-CR and EP-ΝCR was also measured as a function of temperature. The EP-CR solutions showed an increase in light scattering intensity at temperatures below 0 °C. The same observations were made with the fluorescently labeled EPs using DSC, intrinsic viscosity, and light scattering measurements, demonstrating that fluorescently labeling the polymers did not affect their solution properties. However, the high sensitivity of fluorescence enabled us to perform experiments at polymer concentrations as low as 20 mg/L. Experiments were carried out using fluorescence resonance energy transfer and pyrene excimer formation that established the absence of intermolecular association at this polymer concentration. These fluorescence experiments indicate that EP-CR undergoes a transition at 0 °C in toluene consistent with a decrease of the hydrodynamic volume of the polymer coil. These experiments constitute the first evidence that crystallization of semicrystalline EPs in solution can occur intramolecularly.
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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 | 0.001 |
| 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 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".