Nitroxide-Mediated Synthesis of Poly(poly(ethylene glycol) acrylate) (PPEGA) Comb-Like Homopolymers and Block Copolymers
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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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 | 0.000 |
| 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 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".