Styrene/Acrylic Acid Random Copolymers Synthesized by Nitroxide-Mediated Polymerization: Effect of Free Nitroxide on Kinetics and Copolymer Composition
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Bibliographic record
Abstract
Styrene/acrylic acid (S/AA) mixtures were copolymerized in concentrated 50 wt % 1,4-dioxane solutions at 120 °C at two ratios of additional free nitroxide mediator, N,N - tert -butyl- N -[1′-diethylphosphono-2,2′-dimethylpropyl] nitroxide (SG1), relative to 2-[ N - tert -butyl-2,2-(dimethylpropyl)aminooxy]propionic acid (BlocBuilder, Arkema) alkoxyamine unimolecular initiator (4.5 and 9 mol % [SG1]/[BlocBuilder]). Without SG1 at initial acrylic acid monomer feed concentrations f AA,0 > 40 mol %, the apparent rate constants increased sharply, noticeable exotherms were observed, and polydispersities increased from 1.20 at f AA,0 = 0 mol % to 1.48 at f AA,0 = 80 mol %. With 4.5 mol % [SG1]/[BlocBuilder], polymerization rates were slower and not as strongly affected by f AA,0 although exotherms were still noticeable at high f AA,0 . Polydispersities remained ∼1.3 and only increased to >1.4 at high conversions for f AA,0 = 80 mol %. Exotherms were rendered nearly negligible when 9 mol % [SG1]/[BlocBuilder] was used, leading to copolymers with much narrower molecular weight distributions and k p K values for comonomer mixtures bracketed between those of styrene and acrylic acid homopolymerizations at 120 °C ( k p = propagation rate constant, K = equilibrium constant). Copolymer reactivity ratios estimated for samples produced using 9 mol % [SG1]/[BlocBuilder] by nonlinear least-squares minimization were r AA = 0.25 ± 0.11 and r S = 0.93 ± 0.37, in agreement with previous literature.
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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 | 0.000 |
| 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