A Continuous Gradient Colloidal Glass

Colloidal crystals and glasses manipulate light propagation depending on their chemical composition, particle morphology, and mesoscopic structure. This light-matter interaction has been intensely investigated, but a knowledge gap remains for mesostructures comprising a continuous property gradient of the constituting particles. Here, a general synthetic approach to bottom-up fabrication of continuous size gradient colloidal ensembles is introduced. First, the technique synthesizes a dispersion with a specifically designed gradual particle size distribution. Second, self-assembly of this dispersion yields a photonic colloidal glass with a continuous size gradient from top to bottom. Local and bulk characterization methods are used to highlight the significant potential of this mesostructure, resulting in vivid structural colors along, and in superior light scattering across the gradient. The process describes a general pathway to mesoscopic gradients. It can expectedly be transferred to a variety of other particle-based systems where continuous gradients will provide novel physical insights and functionalities.

Characterization of hydrosoluble fraction and oligomers in poly(vinylidene chloride) latexes by capillary electrophoresis using electrophoretic mobility modeling

The characterization of hydrosoluble oligomers in latexes is an important topic in emulsion polymerization since oligomers are suspected to be responsible for latex destabilization. In this work, the hydrosoluble fraction of poly(vinylidene chloride) latexes synthesized by emulsion polymerization of three monomers (acrylic acid, methyl acrylate, vinylidene chloride) was characterized by capillary electrophoresis (CE). CE using direct UV detection permitted to estimate residual monomers and surfactants concentrations contained in the latexes serums. Water soluble oligomers, polymerization initiator (persulfate) and other inorganic anions were detected by indirect UV detection. The oligomers content in the dry extract of serum was estimated to be about 6% (% m/m) represented mainly by 9 different compounds belonging to 3 different families. Using a semi-empirical electrophoretic mobility modeling, the charge number of these oligomers was estimated to be -2 and the molar masses were estimated in the range of ∼300-550 g.mol^-1. Oligomer samples obtained by surfactant-free polymerization, with different initial monomers proportions, provided qualitatively 14 different oligomers, including the 9 oligomers previously detected in the serums. Finally, the latex was characterized (electrophoretic mobility and zeta potential) using its serum as a background electrolyte. This approach could be very useful to study the behavior of the latexes, and possibly destabilization effect, in analytical conditions very close to its real environment / applications.

Methacrylate-based chromatographic media

This review summarizes the preparation and application of chromatographic separation media based on methacrylate monomers with a major focus on highly crosslinked macroporous beads prepared from 2-hydroxyethyl methacrylate and glycidyl methacrylate, respectively. The effects of process variables such as composition of the polymerization mixture that includes monomers, porogenic solvents, and free radical initiator, suspension stabilizer, reaction temperature, and stirring are detailed for both classical and templated suspension polymerization. In addition, specific features of the preparation of monodisperse beads are also discussed. The performance of methacrylate-based separation media is demonstrated on numerous separations in a variety of chromatographic modes.