The effect of block molecular weight distribution on morphologies of polystyrene-block-poly (acrylic acid) aggregates in solution /
Bibliographic record
Abstract
The effect of the molecular weight distribution of both the soluble and the insoluble blocks on the solution self-assembly of the amphiphilic block copolymer polystyrene-block-poly(acrylic acid) was studied. Copolymers of a variety of block lengths but with narrow molecular weight distributions were synthesized by sequential anionic synthesis. Mixing two or more copolymers of differing block length (while the second block length was identical) artificially increased the polydispersity index (PDI) of one block. Self-assembly was induced by adding water slowly to a copolymer solution until a desired solvent composition was attained. The resulting aggregates were compared using transmission electron microscopy and dynamic light scattering. The first experiments, presented in chapter 2, studied the effect of the corona (PAA) polydispersity on the size of vesicular aggregates. For a constant solvent composition and copolymer concentration, the size of the vesicles was generally found to decrease with increasing PAA polydispersity. In chapter 3, a partial phase diagram of morphology as a function of water content and PAA polydispersity is presented. The phase boundaries between spheres and rods, and rods and vesicles were found to shift to lower water contents with increased PAA polydispersity. While chapters 2 and 3 show that the PAA polydispersity affects both the morphology and the size of vesicles, chapter 4 presents work that indicates that the shape of the PAA molecular weight distribution plays an important part in determining the degree to which the PAA polydispersity affects the morphology. A subsequent study also shows that the molecular weight distribution effect only occurs when the relative PAA/PS block length ratio is low. The polystyrene molecular weight distribution studies, presented in chapter 5, show that the opposite effect to that of the PAA molecular weight distribution occurs with an increase in the PS PDI. The morphological boundary from spheres to rods was found to move to higher water contents with an increase in PS PDI. Even at very high water contents, where vesicles are usually found for low molecular weight distribution samples, only spherical micelles were found for the samples with increased PS PDI.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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 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".