Synthesis of Arborescent Polystyrene-<i>g</i><i>raft</i>-polyisoprene Copolymers Using Acetylated Substrates
Bibliographic record
Abstract
A new method is presented for the preparation of arborescent copolymers containing polyisoprene (PIP) segments. The technique uses acetyl coupling sites randomly distributed on polystyrene substrates. Isoprene was polymerized with sec -butyllithium in tetrahydrofuran to yield polyisoprenyllithium, and the living polymer was titrated with an acetylated substrate to generate a copolymer. The grafting yield was maximized at 25 °C using 5 equiv of LiCl to attenuate the reactivity of polyisoprenyllithium. Arborescent copolymers were synthesized by grafting PIP side chains with a weight-average molecular weight M w of either 5000 (PIP5) or 30 000 (PIP30) onto linear, comb-branched (G0), G1, and G2 acetylated polystyrenes. The copolymers with short (PIP5) side chains contain 84−91% w/w polyisoprene. For long (PIP30) side chains, the polyisoprene content varies from 92 to over 97% w/w. The graft copolymers exhibit a geometric increase in branching functionality and molecular weight for successive generations ( f w = 11−4000, M w = 6.5 × 10 4 −2.5 × 10 7 for the PIP5 series, and f w = 11−1530, M w = 3.2 × 10 5 −4.9 × 10 7 for the PIP30 series). A narrow molecular weight distribution ( M w /M n = 1.06−1.09) was maintained after grafting. Film formation by the arborescent copolymers was investigated using tapping mode atomic force microscopy after spin-casting from different solvents. When heptane, a solvent selective for the polyisoprene segments, was used, phase separation between the polystyrene core and the polyisoprene shell was clearly visible in phase contrast imaging, even for copolymers with longer PIP side chains. In nonselective solvents (toluene and chloroform) phase contrast was reduced, presumably due to enhanced mixing of the polystyrene and polyisoprene phases.
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How this classification was reachedexpand
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 | 0.001 | 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 teacher head, 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".