Conformation of intramolecularly cross-linked polymer nanoparticles on solid substrates.

Dukette, Tiffany E; Mackay, Michael E; Van Horn, Brooke; Wooley, Karen L; Drockenmuller, Eric; Malkoch, Michael; Hawker, Craig J · Nano Lett · 2005

basic_science · Level V

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Abstract

The conformation of cross-linked, monomolecular, polystyrene nanoparticles on a solid substrate is considered as a function of cross-linking degree and substrate surface free energy. It is found that an extreme amount of cross-linking is necessary for the ca. 5-10 nm diameter nanoparticles to retain their original spherical shape, regardless of surface free energy. A lesser amount of cross-linking produces a nanoparticle that collapses to a pancake-like conformation on a high-energy substrate yet remains spherical on a low-energy surface. A simple model is developed to reveal the relationship between nanoparticle modulus and surface free energy to define the nanoparticle conformation.