POLY 473 |
| Conformational changes of multiblock polydimethylsiloxane-b-poly(methacrylic acid) (PDMS-b-PMA) copolymers in aqueous solutions triggered by concentration variations were observed in two PDMS-b-PMA systems, MB1 and MB2, having the same ratio between the two blocks, but differing in the block size. The PDMS blocks in MB1 and MB2 had 12 and 2 repeat units, respectively. The nitroxide spin probe used was 5-doxyl-decane (5DD). As reference, the ESR spectra of the probe were measured in water, aqueous PDMS, aqueous PMA, and aqueous PDMS and PMA mixtures. The 14N isotropic hyperfine splitting, aN, varied between 14.1 G in PDMS solutions (nonpolar media) to 15.8 G in PMA solutions. Two spectra components were detected in MB1 (long PDMS blocks); in MB2 (shorter PDMS blocks) the probe was present in three regions: hydrophobic, hydrophilic, and a slow PDMS component with extreme separation of 64 G. Spectra simulation and quantitative determination of the intensity ratio of the probe in the various sites were interpreted in terms of different micellization mechanisms for the two systems: a one stage micellization for MB1, and a two stage micellization for MB2: the size of the blocks affects not only the CMC, but also the micellization process. |
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Multicompartment Micelles: Higher Order Self-Assembly of Block Copolymers
6:00 PM-8:00 PM, Tuesday, 12 September 2006 Moscone Center -- Hall D, Poster
Division of Polymer Chemistry |