Multiparticle Effects on the Interactions of Complex Colloidal Dispersions

Abstract

A model polymer colloid with simple "recognition" ability was synthesized by dispersion polymerization using comb copolymer stabilizers that incorporate both 23-unit poly(ethylene oxide) and C18H37 side chains. Force interactions between beads of the resulting latex were examined using colloid-probe atomic force microscopy (CAFM) and Langmuir compression (LC). CAFM measurements showed an initial repulsion between beads on close approach that gives way to a strong bridging attraction and a minimum in the force-distance profile at bead surface separations comparable to twice the hydrocarbon side chain dimensions. By contrast, latex beads stabilized with combs that incorporate only the (EO)23 side chains exhibited purely repulsive behavior. LC experiments on the same systems produced pressure-area isotherms qualitatively similar to the CAFM data; however, significant forces were registered at monolayer bead densities corresponding to surface separation distances 1-2 orders of magnitude larger than the side chain dimensions and comparable to the bead size (∼1 µm). A simple model was developed to connect the data from these two experiments into a unified picture of how particle surface chemistry is expressed in the multiparticle behavior of complex colloidal dispersions.

Compression of Langmuir Films Composed of Fine Particles: Collapse Mechanism and Wettability

“…[2][3][4][5][6][7][8] The organization of particles into different structures at interfaces also attracted significant attention, since this phenomenon can serve as a model for colloid aggregations, flotation, 9 phase transitions, [10][11][12][13][14][15][16] and interfacial thermodynamics and interactions. [17][18][19][20][21][22][23][24][25][26][27][28] Moreover, the nanoparticulate arrays at liquid-fluid interfaces can provide an entry into the fabrication of nanostructural, solid-supported films. [29][30][31][32][33][34][35][36] The wettability of particles plays an important role in the aforementioned processes and phenomena, because it can relate to the particle-particle (p-p) colloid and capillary interactions.…”

Evidence for Secondary Minimum Flocculation of Stöber Silica Nanoparticles at the Air−Water Interface: Film Balance Investigations and Computer Simulations

“…The measurement of the effective surface tension of a monoparticulate layer using a film balance or by another way can provide an experimental tool for the study of particle−particle (p−p) interactions at liquid−fluid interfaces. − Though the method has been known for about forty years, it could not spread widely because of many difficulties (contaminations of model particles, − particle loss due to the spreading process, cohesive film formation due to the hydrophobic forces, − etc.) and the lack of suitable model particles.…”

Controlled chain branching free radical polymerization manipulate with trithiocarbonates

“…Branched polymers with different architectures have received tremendous attention in recent decades, not only because of their rich morphological textures,1, 2 but also because of their potential applications, such as compatibilizer in polymer blends,3 as surface modifiers for uses as coatings, adhesives, dispersants, and etc 4, 5. Most hyperbranched polymers are synthesized by step‐growth polymerization via polycondensation of AB x monomers.…”