Synthesis of Thermoresponsive Mixed Arm Star Polymers by Combination of RAFT and ATRP from a Multifunctional Core and Its Self-Assembly in Water
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Bibliographic record
Abstract
Mixed arm star copolymers of poly( N,N -dimethylacrylamide) (PDMA) and poly( N -isopropylacrylamide) (PNIPAm) were synthesized by a sequential reversible addition−fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP) from a multi-initiator-functionalized hyperbranched polyglycerol (MI-HPG) core. The MI-HPG core was synthesized from an amine-functionalized polyglycerol, modified successively with 2-chloropropionamide groups (ATRP initiator) and 4,4′-azobis(4-cyanovaleric acid) (azo initiator). N,N- Dimethylacrylamide was polymerized from MI-HPG core by the RAFT method using S, S′ -bis(α,α′-dimethyl-α′′-acetic acid)trithiocarbonate as a chain transfer agent (CTA) in acetic acid/sodium acetate aqueous buffer solutions. The ratio of [CTA]/[azo initiator] was critical in controlling the molecular weight of the PDMA grafts from MI-HPG core (HPG- g -PDMA). Controlled synthesis of mixed arm star copolymers was achieved by cografting PNIPAm on to the HPG- g -PDMA macroinitiator by ATRP. The temperature-induced phase transition of aqueous solutions of hybrid HPG- g -PDMA/PNIPAm star copolymers was studied by 1 H NMR, UV−vis spectroscopy, and laser light scattering. Results show that the mixed arm star copolymers exist as either single molecules or small aggregates below the phase transition temperature (LCST) of PNIPAm in aqueous solutions. All the star copolymers formed intermolecular aggregates above the LCST of PNIPAm possibly due to the hydrophobic interaction between collapsed PNIPAM chains. These aggregates have micelle-like structure with PNIPAm core and PDMA corona. The formation of intermolecular aggregates and the stabilization of aggregates depend on the molecular weight of arms and composition of the star copolymer.
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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) | 0.000 | 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) | 0.000 | 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