Effect of an Acid Protecting Group on the “Livingness” of Poly(acrylic acid-ran-styrene) Random Copolymer Macroinitiators for Nitroxide-Mediated Polymerization of Styrene
Bibliographic record
Abstract
Poly(acrylic acid-ran-styrene) (P(AA-r-S)) and poly(tert-butyl acrylate-ran-styrene) (P(tBuA-r-S)) random copolymers previously made with different molar ratios (0, 4.5 and 9 mol%) of additional free nitroxide mediator, N-tert-butyl-N-[1′-diethylphosphono-2,2′-dimethylpropyl] nitroxide (SG1), relative to 2-[N-tert-butyl-2,2-(dimethylpropyl)aminooxy]propionic acid (BlocBuilder ® ) alkoxyamine unimolecular initiator were used as macroinitiators for styrene chain extension.The reinitiating experiments were performed in bulk at 115 o C when using P(tBuA-r-S) macroinitiators or 30-50 wt% dioxane solution at 120 o C when using P(AA-r-S) macroinitiators.The P(tBuA-r-S) containing macroinitiators (number average molecular weight = 13.4-25.8kg•mol -1 ) with polydispersities = 1.13-1.57were capable of initiating chains extended with styrene as indicated by monomodal and narrow molecular weight distributions with 's = 34.6-66.3kg•mol -1 and 's ranging from 1.24-1.39.Unprotected P(AA-ran-S) acrylic acid containing macroinitiators ( = 19.7-28.8kg•mol -1 ) with 's ranging from 1.34-1.48also initiated chain extensions with styrene but tended to have much higher 's of 1.50-2.47.In some cases, dead chains that failed to re-initiate were clearly observed from the gel permeation chromatograms.The acrylic acid likely degraded the alkoxyamine as suggested by previous literature, reducing the SG1active chain end concentration and thereby decreasing the control of the molecular weight distribution.Based on these findings, a more desirable route towards higher molecular weight poly(acrylic acid) containing block copolymers by nitroxide-mediated polymerization is likely done by polymerization of the protected acrylic acid followed by suitable deprotection.
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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) | 0.001 | 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) | 0.002 | 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".