Surface modification of nanoparticles with polymer ligands has emerged as an important strategy to control interactions and assembly in colloidal systems. Recent research has revealed that the tethering of polymeric ligands to the surface of nanoparticles (so called ‘particle brush’) can induce the autonomous organization of multicomponent particle brush mixtures into monotype domain structures in a process that bears similarity to phase separation in binary polymer blends. Interest in this autonomous and reversible phase separation mechanism is motivated by the potential transformative applications in the high-throughput fabrication of solid films and smart coating technologies. We will present recent results on the phase separation behavior of particle brush blend in thin films and bulk films. Previous studies have revealed the scaling coefficient for domain coarsening (d ~ t0.2) in particle brush blend to be distinctively different from the scaling observed in classical linear polymer blends (d ~ t0.33). This points to fundamental differences of the dynamical processes that control domain growth. To elucidate the origin of this anomalous diffusion kinetics, phase separation mechanism was evaluated via TEM techniques in thin film state and via small angle neutron scattering (SANS) experiments in bulk film state. A novel synthetic method to enable continuous variation of the scattering length density of organosilica nanoparticles will be presented and PMMA or PSAN tethers have been isotopic labeled by random copolymerization of appropriate amounts of d8-MMA or d8-S monomers via SI-ATRP. Key to our approach is the use of contrast matching condition between particle core and polymer brush to avoid scattering contributions from particle cores (to simplify SANS analysis and to enable early-state domain characterization). This contribution can yield fundamentally new insights into the kinetics of phase separation and provide a better understanding of the role of polymeric ligands on the interactions and assembly formation in particulate materials.

Elucidation of ligand-driven segregation in multicomponent hybrid particles for dynamic assembly of nanostructures

ACS Fall 2021

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