Nitroxide-Mediated Synthesis of Poly(poly(ethylene glycol) acrylate) (PPEGA) Comb-Like Homopolymers and Block Copolymers
Why this work is in the frame
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Bibliographic record
Abstract
The kinetics of poly(ethylene glycol) acrylate (PEGA) nitroxide-mediated polymerization in bulk were studied at two temperatures (115 and 125 °C) and at initial molar ratios r = 0.05−0.21 of added free nitroxide ( N - tert -butyl- N -[1-diethylphosphono-(2,2-dimethylpropyl)] nitroxide (SG1) relative to the unimolecular initiator 2-methyl-2-[ N - tert -butyl- N -(diethoxylphosphoryl-2,2-(dimethylpropyl)aminooxy]propionic acid (BlocBuilder) ( r = [SG1] 0 /[BlocBuilder] 0 ). Bulk polymerizations were more controlled at 115 °C with r = 0.10−0.21 giving polymers with polydispersity indices ( M̅ w / M̅ n ) as low as 1.17 and a linear increase in number average molecular weight M̅ n with conversion up to about 50%. The k p K values ( k p = propagation rate constant, K = equilibrium constant) for PEGA at 115 °C were 1.9 × 10 −5 s −1 to 2.9 × 10 −5 s −1 and at 125 °C were 6.7 × 10 −5 to 8.3 × 10 −5 s −1 . PEGA polymerizations in dimethylformamide (DMF) or anisole solution were most controlled when conducted in 25 wt % solutions, r ∼ 0.15 and lower temperatures (95−115 °C) but side reactions were prevalent and control was not significantly better than in bulk. Chain extension of a comb-like poly(PEGA) (PPEGA, M̅ n = 8.1 kg/mol, M̅ w / M̅ n = 1.20) with styrene in 50 wt % DMF solution at 115 °C to produce a PPEGA−poly(styrene) (PPEGA−PS) block copolymer indicated sufficient “livingness” of the PPEGA chain ends as observed by the steady increase in M̅ n and monomodal molecular weight distribution as determined by size exclusion chromatography although some broadening of the molecular weight distribution was evident ( M̅ n = 62.3 kg/mol and M̅ w / M n = 1.53). 1 H NMR spectroscopy revealed resonances corresponding to the styrenic and PEGA segments and differential scanning calorimetry revealed two distinct glass transition temperatures T g indicative of the PPEGA ( T g ≈ −70 °C) and PS ( T g ≈ 98 °C) segments.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| 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 it