Abstract
Recently-developed photo-crosslinkable PMMA (polymethylmethacrylate) colloidal spheres are a highly promising system for fundamental studies in colloidal physics and may have a wide range of future technological applications. We synthesize these colloids and characterize their size distribution. Their swelling in a density- and index- matching organic solvent system is demonstrated and we employ dynamic light scattering (DLS), as also the recently-developed confocal differential dynamic microscopy (ConDDM), to characterize the structure and the dynamics of a fluid bulk suspension of such colloids at different particle densities, detecting significant particle charging effects. We stretch these photo-crosslinkable spheres into ellipsoids. The fact that the ellipsoids are cross-linked allows them to be fluorescently stained, permitting a dense suspension of ellipsoids, a simple model of fluid matter, to be imaged by direct confocal microscopy.
Highlights
Colloids, micron-size particles suspended in a solvent, are ubiquitous in nature and technology and may serve as a simple physical model for the phase behavior of atoms and molecules
In order to characterize the shape of the spherical colloidal particles, we deposit them from hexane onto a clean glass microscopy slide, dry the sample under vacuum, and obtain scanning electron microscopy (SEM) images at 5–30 keV, employing the Quanta Inspect (FEI, Hillsboro, OR, USA) (FEITM )
While an identical particle size is obtained by both dynamic light scattering (DLS) and confocal differential dynamic microscopy (ConDDM), the size obtained by SEM is smaller by ~10%, indicative of particle swelling in organic solvents
Summary
Micron-size particles suspended in a solvent, are ubiquitous in nature and technology and may serve as a simple physical model for the phase behavior of atoms and molecules. The stretched PCPMMA spheres are photo-crosslinked in their ellipsoidal state; high-temperature procedures are employed to load the particles with a fluorescent dye and to covalently link PHSA to their surface. Such procedures are impossible with the common PMMA particles, which would turn spherical if heated to a high temperature. We demonstrate that the particles significantly swell in this solvent The structure of these suspensions and their dynamics, which we measure by the recently-developed confocal differential dynamic microscopy (ConDDM) [19], indicate that the particles are charged much more strongly than the common sterically-stabilized PMMA colloids in a similar solvent [20,21,23]. We demonstrate that the particles can be stretched into an ellipsoidal shape, fluorescently-labeled, and resuspended in a solvent for confocal studies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
