Abstract
Nearly monodisperse poly(methyl acrylate) (PMA) and spherical SiO 2 nanoparticles (NP, d = 14 ± 4 nm) were co-cast from 2-butanone, a mutually good solvent and a displacer of adsorbed PMA from silica. The effects of NP content and post-casting sample history on the dispersion morphology were found by small-angle X-ray scattering supplemented by transmission electron microscopy. Analysis of the X-ray results show that cast and thermally annealed samples exhibited a nearly random particle dispersion. That the same samples, prior to annealing, were not well-dispersed is indicative of thermodynamic miscibility during thermal annealing over the range of NP loadings studied. A simple mean-field thermodynamic model suggests that miscibility results primarily from favorable polymer segment/NP surface interactions. The model also indicates, and experiments confirm, that subsequent exposure of the composites to the likely displacer ethyl acetate results in entropic destabilization and demixing into NP-rich and NP-lean phases.
Original language | English (US) |
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Pages (from-to) | 4920-4927 |
Number of pages | 8 |
Journal | Macromolecules |
Volume | 44 |
Issue number | 12 |
DOIs | |
State | Published - Jun 28 2011 |
Externally published | Yes |