Abstract
Model colloidal systems studied with confocal microscopy have led to numerous insights into the physics of condensed matter. Though confocal microscopy is an extremely powerful tool, it requires a careful choice and preparation of the colloid. Uncontrolled or unknown variations in the size, density, and composition of the individual particles and interactions between particles, often influenced by the synthetic route taken to form them, lead to difficulties in interpreting the behavior of the dispersion. Here we describe the straightforward synthesis of copolymer particles which can be refractive index- and density-matched simultaneously to a non-plasticizing mixture of high dielectric solvents. The interactions between particles are accurately tuned by surface grafting of polymer brushes using Atom Transfer Radical Polymerization (ATRP), from hard-sphere-like to long-ranged electrostatic repulsion or mixed charge attraction. We also modify the buoyant density of the particles by altering the copolymer ratio while maintaining their refractive index match to the suspending solution resulting in well controlled sedimentation. The tunability of the inter-particle interactions, the low volatility of the solvents, and the capacity to simultaneously match both the refractive index and density of the particles to the fluid opens up new possibilities for exploring the physics of colloidal systems.
Highlights
Model colloidal systems studied with confocal microscopy have led to numerous insights into the physics of condensed matter
Colloidal systems are used to explore the physics of condensed matter in real-time and space; observations of the behavior of colloidal particles have led to unprecedented insight into phenomena as varied as crystal nucleation[1] and melting[2], defect transport[3], glass formation[4,5], wetting and capillary phenomena[6], and self-assembly and specific bonding[7]
We describe the synthesis of a colloidal model system composed of monodisperse particles that can be simultaneously refractive index- and density-matched to mixtures of non-hazardous, polar solvents that do not plasticize the particles whose surfaces may be modified with polymer brushes grafted using Atom Transfer Radical Polymerization (ATRP)
Summary
Model colloidal systems studied with confocal microscopy have led to numerous insights into the physics of condensed matter. Colloidal systems are used to explore the physics of condensed matter in real-time and space; observations of the behavior of colloidal particles have led to unprecedented insight into phenomena as varied as crystal nucleation[1] and melting[2], defect transport[3], glass formation[4,5], wetting and capillary phenomena[6], and self-assembly and specific bonding[7] Unlike their atomic counterparts, the structure, dynamics, and mechanical properties of these dispersions are accessible by optical microscopy and light scattering. We describe the synthesis of a colloidal model system composed of monodisperse particles that can be simultaneously refractive index- and density-matched to mixtures of non-hazardous, polar solvents that do not plasticize the particles whose surfaces may be modified with polymer brushes grafted using Atom Transfer Radical Polymerization (ATRP). We prepare these copolymer particles containing a fluorescent core and a non-fluorescent shell that enhances the accuracy of particle locating in densely-packed 3D confocal experiments[27,28]
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