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Título: Nanoparticle size control and coronal structure in block ionomer micelles
Autores: Moffitt, Matthew.
Fecha: 1997
Publicador: McGill University - MCGILL
Fuente:
Tipo: Electronic Thesis or Dissertation
Tema: Chemistry, Physical.
Chemistry, Polymer.
Descripción: Quantum-confined semiconductors have been synthesized in ionomer microdomains, demonstrating thermodynamic control of nanoparticle sizes via a priori knowledge of ion aggregation numbers. In block ionomers, cadmium sulfide (CdS) nanoparticle sizes are found to scale with the ionic block length (N B) as NB3/5. CdS-polymer composites from block ionomers can be suspended in organic solvents as reverse micelles. Micelle stability is improved by reneutralization of acrylic acid blocks surrounding the nanoparticle. Reloading of microreactors and controlled continued growth of nanoparticles is demonstrated. Novel assemblies of CdS-containing reverse micelles are formed by secondary self-assembly in aqueous media. Scaling relations are also determined for microreactors containing different metal ions. For all metal ions investigated, the ionic core size scales as NB0.58+/-0.03, in agreement with starlike models; the proportionality constant is found to depend on the metal ion.
Coronal structure in block ionomers has been investigated by small-angle neutron scattering (SANS), using deuterated labels at various distances from the ionic core. Near the outside of the polymer brush, the scattered intensity scales with the scattering vector (q) as q --5/3, suggesting a semidilute environment for the label. Chain conformations are influenced by neighbouring coronae above the micelle overlap concentration. Closer to the ionic core, the chains become more crowded, and the semidilute assumption is not applicable. For labels directly connected to the core, intensity scaling suggests highly extended chains.
Idioma: en