Model colloidal systems studied with confocal microscopy have resulted in numerous insights in to the physics of Belnacasan condensed matter. thickness of the contaminants by changing the copolymer proportion while preserving their refractive index match towards the suspending option leading to well managed sedimentation. The tunability from the inter-particle connections the reduced volatility from the solvents and the capability to concurrently match both refractive index and thickness of the contaminants to the liquid opens up brand-new possibilities for discovering the physics of colloidal systems. Colloidal systems are accustomed to explore the physics of condensed matter in real-time and space; observations from the behavior of colloidal contaminants have resulted in unprecedented insight into phenomena as varied as crystal nucleation1 and melting2 defect transport3 glass formation4 5 wetting and capillary phenomena6 and self-assembly and specific bonding7. Unlike their atomic counterparts the structure dynamics and mechanical properties of these dispersions are accessible by optical microscopy and light scattering. However practical limitations of each of these techniques and the design of individual experiments makes control over the physical properties of the constituent particles essential. Optical microscopy which reveals the real-space structure of colloids and light scattering which elucidates the structure and dynamics in reciprocal space rely on the precise control of the size and refractive index of the observed particles: as the choice of particle size influences the relative time and length scales available to the experiment and the careful matching of the refractive indexes of the particles and suspending fluid minimizes the effects of optical aberrations and multiple scattering. To study the evolution of samples over long time scales it is essential the evaporation of the solvent is usually minimal; this is particularly important during rheological measurements in which the suspensions are exposed to the environment. Gravitational stresses which cannot be ignored for micrometer scale particles result in density gradients and sedimentation that strongly affect material properties such as crystal nucleation rates8. These detrimental effects of gravity can be minimized by matching the density of the particles to that of the suspending fluid: thus enabling the study of equilibrium bulk behavior. Nevertheless a well controlled density mismatch can be desirable6 9 10 for example when templating specific crystalline structures on a patterned surface11 12 13 In addition to the physical properties of individual particles and the surrounding fluid the structure and dynamics of colloidal suspensions are also determined by the forces that particles exert on each other14 15 16 The simplest conversation between solid particles is usually that of volume exclusion; in this so-called hard-sphere limit particles are assumed to be impenetrable and the phase behavior is usually governed by particle volume fraction alone. Two commonly used experimental systems that exhibit such Rabbit Polyclonal to SFRS4. a hard-sphere conversation potential and may be refractive index- and density-matched are poly (methyl methacrylate) (PMMA) microspheres stabilized by a brush of poly(hydroxystearic acid) (PHSA-PMMA) dispersed in a mixture of low Belnacasan dielectric organic solvents15 16 and stearylated-silica dispersed in halogenated fluids17. However despite the low polarity of these solvents trace amounts of ionizable impurities dissolved in these oils can charge particle surfaces in ways that are hard to predict and control16 18 muddling otherwise purely hard-sphere interactions. Moreover the most Belnacasan commonly used Belnacasan hard-sphere system PHSA-PMMA is usually often dispersed in fluid mixtures in which one or more of its components swells the polymer that composes the particles sometimes by as much as several tens of percents. This may be expected to significantly lower the glass transition heat softening the particles and changing their properties over time16. Finally while this particular system has proven invaluable as a colloidal model system it synthesis is usually notoriously difficult to reproduce. More elaborate inter-particle interactions can be designed by adding polymers or surfactants to.