Relationship between Wall Thickness and Size in Block Copolymer Vesicles
Notice bibliographique
Résumé
In this study, we report a new phenomenon dealing with the size-dependent behavior of the wall thickness of block copolymer vesicles, especially the decrease in wall thickness with decreasing vesicle size. Four vesicle-forming copolymers from the polystyrene-b-poly-(acrylic acid) (PS-b-PAA) family (i.e., PS(500)-b-PAA(50), PS(310)-b-PAA(28), PS(240)-b-PAA(15), and PS(412)-b-PAA(46)) were chosen for study. The sizes and wall thicknesses of the vesicles after quenching were determined from the TEM micrographs, and plots were made of the wall thickness versus size for each family of vesicles made from each of the various blocks. First, the effect of the length of the PAA block on the relationship between the wall thickness and the size was examined. In the vesicles prepared from PS(500)-b-PAA(50), the copolymer with the longest PAA block that yields the smallest vesicles, the wall thickness decreases strongly with decreasing size. By contrast, in the case of vesicles made from PS(240)-b-PAA(15), for which a wide size distribution is obtained, only a weak size dependence of the wall thickness is seen. For vesicles made from the copolymer with intermediate PAA block length (i.e., PS(310)-b-PAA(28)), both strong and weak behavior regions are observed depending on the vesicle size range. We suggest that this new phenomenon of the size dependence of the wall thickness can be considered to be another stabilization mechanism for very small vesicles, under conditions where chain segregation is insufficient to stabilize the size. The vesicles can be stabilized by decreasing the wall thickness for very small vesicles, resulting in the increase in area per corona chain, thus decreasing the corona repulsion on the inside. The effects of additives such as NaCl, HCl, or NaOH on the relationship between the wall thickness and the size were also investigated. By shielding the electrostatic repulsion among corona chains in the presence of NaCl, the strong behavior of the vesicles prepared from PS(412)-b-PAA(46) changes to a weak one as the width of the vesicle size distribution increases. In a NaCl concentration region around 10 mM, an opposite effect is seen relative to that observed in small vesicles in that the wall thickness decreases with increasing vesicle size for vesicles larger than ca. 300 nm, an effect ascribed to corona repulsion among the external corona chains. The addition of HCl also drives the relationship to be weaker through the protonation of the carboxylate groups of PAA chains, in an effect similar to that of NaCl. The presence of NaOH is expected to strengthen the relationship via the deprotonation of PAA, which increases the corona repulsion. However, because of the very short length of PAA chains in the system where a weak effect is seen, no significant effect of NaOH addition was observed because the size distribution remained broad.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».