Direct Synthesis of Well-Defined Quaternized Homopolymers and Diblock Copolymers via ATRP in Protic Media
Bibliographic record
Abstract
The direct synthesis of well-defined cationic homopolymers and block copolymers based on methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate [MeDMA] by ATRP in protic media at 20 °C is described. Homopolymerization of MeDMA in purely aqueous media was fast and poorly controlled, leading to a relatively high polydispersity of 1.37 and low initiation efficiency. Addition of Cu(II)Br 2 led to slower polymerizations but only slightly lower polydispersities. Addition of methanol also reduced the rate of polymerization and produced narrower molecular weight distributions. Unfortunately, 1 H NMR studies indicated that transesterification of MeDMA with methanol produced significant quantities of methyl methacrylate (MMA) on the time scale of the polymerization; this side reaction led to the unwanted production of MeDMA−MMA statistical copolymers. This problem was alleviated by replacing the methanol cosolvent with 2-propanol, since the secondary alcohol was much less prone to transesterification. High conversions were obtained with a 1:1 2-propanol/water composition within a few hours at 20 °C, but partial phase separation occurred toward the end of the polymerization, particularly at higher monomer concentration. Although nonlinear kinetic plots were observed, final polydispersities were relatively low (ranging from 1.19 to 1.27, according to aqueous GPC studies), and good self-blocking efficiencies were demonstrated in chain extension experiments. A range of new cationic diblock copolymers were prepared either by using a poly(ethylene oxide)-based macroinitiator or via sequential monomer addition with various hydrophilic methacrylates such as glycerol monomethacrylate, [2-(methacryloyloxy)ethyl]phosphorylcholine, the benzyl chloride-quaternized analogue of MeDMA, and the sulfobetaine adduct of the reaction of 2-(dimethylamino)ethyl methacrylate with 1,3-propane sultone, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide. Potential applications for these cationic diblock copolymers include novel gene/oligonucleotide transfer agents and also polymeric templates for the catalytic formation of silica in aqueous solution under mild conditions.
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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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".