Micelles Formed by a Model Hydrogen-Bonding Block Copolymer
| Autor: | Nitash P. Balsara, H. S. Jeon, Jianqun Zhao, Eli M. Pearce, T. K. Kwei, P. K. Kesani |
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| Rok vydání: | 1995 |
| Předmět: | |
| Zdroj: | Macromolecules. 28:1972-1978 |
| ISSN: | 1520-5835 0024-9297 |
| Popis: | A nearly monodisperse polystyrene-block-poly(p-hydroxystyrene) copolymer (PS-PSOH) was synthesized by combining protected group chemistry with high-vacuum anionic polymerization. The molecular weight of both blocks was 1.0×10 4 . Our objective was to study the effect of hydrogen bonding on micelle formation in block copolymer solutions. The self-hydrogen-bonding capability of the hydroxystyrene moieties is well established. Light scattering experiments were conducted on dilute solutions of PS-PSOH in tetrahydrofuran (THF), a common solvent for both blocks, and toluene, a selective solvent for the polystyrene block. Dynamic light scattering (DLS) measurements indicated that the block copolymer was molecularly dispersed (or nearly so) in THF with a hydrodynamic radius R h =3.8 nm. However, large aggregates with R h =76 nm were observed by DLS in toluene solutions. Static light scattering (SLS) measurements on the PS-PSOH/toluene solutions confirmed the presence of large aggregates with aggregation numbers of 10 4 chains/micelle. The micellar structure was determined by enforcing simultaneous consistency with both SLS and DLS measurements. A rodlike structure, 300 nm in length and 40 nm in diameter, is consistent with both measurements |
| Databáze: | OpenAIRE |
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