Formation of Colloidally Stable Phase Separated Poly(<i>N</i>-vinylcaprolactam) in Water: A Study by Dynamic Light Scattering, Microcalorimetry, and Pressure Perturbation Calorimetry
Why this work is in the frame
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Bibliographic record
Abstract
The effect of temperature on aqueous solutions of poly( N -vinylcaprolactam) (PVCL) samples of molecular weights ranging from 21 000 to 1.5 × 10 6 g mol -1 was monitored by dynamic light scattering (DLS), high-sensitivity microcalorimetry (HS DSC), and pressure perturbation calorimetry (PPC) from 10 to 80 °C. The polymer was soluble in cold water and underwent phase separation at T CP ∼ 31−38 °C, depending on the molecular weight. The phase transition was endothermic, with an enthalpy change of 4.4 ± 0.4 kJ mol -1 . Stable particles of average diameters 80 nm (high molecular weight PVCL) and ∼ 180 nm (low molecular weight PVCL) formed above the phase transition temperature. The coefficient of thermal expansion of PVCL in water (α pol ), determined by PPC, underwent a sharp decrease at the temperature corresponding to the onset of phase transition, then it passed through a maximum, and decreased continuously with increasing temperature. The stability of the particles formed in PVCL solutions kept at temperatures exceeding T CP suggests that their surfaces possess a hydrophilic character. Results of microcalorimetric measurements carried out with solutions of PVCL in D 2 O add further strength to this conclusion. The thermodynamic and volumetric changes associated with the phase transition of aqueous PVCL solutions are compared to those of aqueous solutions of poly( N -isopropylacrylamide) (PNIPAM), a polymer that also undergoes a phase transition in water at ∼ 31 °C, and of poly(vinylpyrrolidone) (PVP), a polymer structurally related to PVCL, which is soluble in water at all the temperatures investigated here.
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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) | 0.000 | 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 it