title: Micellar structures of poly(styrene-b-4-vinylpyridine)s in THF/toluene mixtures and their functionalization with gold.
abstract: The effects of the block copolymer composition and the solvent selectivity on the micellar morphologies of poly(styrene- b-4-vinylpyridine)s (PS- b-P4VPs) and their functionalizations with gold were studied in 10 mg/mL solutions using small-angle X-ray scattering and transmission electron microscopy (TEM). The solvent selectivity for the PS block was controlled by toluene/tetrahydrofuran (THF) mixtures in which toluene and THF are selective for PS and nonselective, respectively. The micellar structure was strongly dependent on phi (wt % toluene in toluene/THF mixture) and the composition of the block copolymers. PS(12K)- b-P4VP(11.8K) (symmetric) showed spherical micelles in the entire range of phi except phi = 0 (THF, nonselective solvent). PS(3.3K)- b-P4VP(18.7K) (asymmetric, longer P4VP) showed multiple morphologies with transitions from spheres to cylinders and finally to vesicles with an increase in phi. PS(19.6K)- b-P4VP(5.1K) (asymmetric, longer PS) showed spherical micelles only at the narrow ranges of 90 wt % <or= phi <or= 100 wt % and an isotropic state at the other ranges. The micelles formed a complex with HAuCl 4 and were reduced with hydrazine in the solvent mixtures. The morphologies of micelles, hybrid micelles, and gold nanoparticles were investigated by using TEM and UV/vis spectroscopy. The possible mechanisms leading to these morphological changes and the formation of the nanosized gold particles were also discussed.
authors.affiliation: Department of Polymer Science, Kyungpook National University, 1370 Sangyuk-dong, Buk-gu, Daegu 702-701, Korea.
authors.forename: Nauman
authors.initials: N
authors.lastname: Ali
authors.forename: Soo-Young
authors.initials: SY
authors.lastname: Park
mesh_terms: D005663:Furans / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles; D036103:Nanotechnology / Q000379:methods; D011108:Polymers / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry*; D011145:Polyvinyls / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D012542:Scattering, Radiation; D012997:Solvents / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013499:Surface Properties; D014050:Toluene / Q000737:chemistry*; D014965:X-Rays
chemical_list: D005663:Furans; D008823:Micelles; D011108:Polymers; D011137:Polystyrenes; D011145:Polyvinyls; D011725:Pyridines; D012997:Solvents; C509607:polystyrene-block-poly(4-vinylpyridine); D014050:Toluene; C018674:tetrahydrofuran; D006046:Gold