Preparation of Colloidal Organosilica Spheres through Spontaneous Emulsification

Abstract

Colloidal particles of controlled size are promising building blocks for the self-assembly of functional materials. Here, we systematically study a method to synthesize monodisperse, micrometer-sized spheres from 3-(trimethoxysilyl)propyl methacrylate (TPM) in a benchtop experiment. Their ease of preparation, smoothness, and physical properties provide distinct advantages over other widely employed materials such as silica, polystyrene, and poly(methyl methacrylate). We describe that the spontaneous emulsification of TPM droplets in water is caused by base-catalyzed hydrolysis, self-condensation, and the deprotonation of TPM. By studying the time-dependent size evolution, we find that the droplet size increases without any detectable secondary nucleation. Resulting TPM droplets are polymerized to form solid particles. The particle diameter can be controlled in the range of 0.4 to 2.8 μm by adjusting the volume fraction of added monomer and the pH of the solution. Droplets can be grown to diameters of up to 4 μm by adding TPM monomer after the initial emulsification. Additionally, we characterize various physical parameters of the TPM particles, and we describe methods to incorporate several fluorescent dyes.

Colloid supported lipid bilayers for self-assembly

“…However, once such substrates were first coated with a silica shell, the bilayer was found to be both homogeneous and mobile. Unexpectedly, particles made from an organosilica compound (TPM) whose surfaces are similar to silica [34] only showed homogeneous, but not mobile bilayers. Since silica, TPM and polystyrene colloids were all negatively charged, we conclude that the chemical composition of the substrate and not only the surface charge plays a fundamental role in the homogeneity and fluidity of the bilayer.…”

“…Silica spheres (Stöber method, Microparticles GmbH) −56 ± 6 yes yes Hematite cubic particles [31] +39 ± 5 no no Silica-coated hematite cubic particles [32] −32 ± 6 yes yes Polystyrene spheres (Sigma Aldrich) −38 ± 2 no no Polystyrene spheres with carboxyl groups [36] −43 ± 1 no no Silica-coated Polystyrene-TPM anisotropic particles [11] −33 ± 1 yes yes TPM spheres [34] −42 ± 1 yes no TPM spheres with carboxyl groups [35] −46 ± 1 no no TPM spheres with amino groups [35] −12 ± 4 no no Figure 2: Effect of surface roughness on lipid bilayer formation. Scanning electron microscopy images (SEM) images of A) a smooth and C) rough polystyrene-TPM particle coated with silica.…”

Automated tracking of colloidal clusters with sub-pixel accuracy and precision

“…For two-dimensional diffusion measurements we employed samples consisting of partially clustered TPM (3-(trimethoxysilyl)-propylmethacrylate) colloids with a diameter of 2.05 µm containing a FITC (fluorescein isothiocyanate) fluorescent marker, as described in [39]. Particles were confined to the microscope coverslip through sedimentation.…”

Self‐assembly of block copolymers with an alkoxysilane‐based core‐forming block: A comparison of synthetic approaches

“…The hydrolysis and condensation of an alkoxysilane-functional monomer ((3-trimethoxysilyl)propyl methacrylate, MPS) in water has also been previously utilized to prepare colloidal nanocomposites. [43][44][45][46] van der Wel et al recently demonstrated a simple method for the formation of colloidal organosilica of varying particle size by stirring MPS in water at room temperature, using ammonium hydroxide as a catalyst. 43 Other work using MPS to prepare hybrid colloids by emulsification also use base catalysis at room temperature.…”

“…[43][44][45][46] van der Wel et al recently demonstrated a simple method for the formation of colloidal organosilica of varying particle size by stirring MPS in water at room temperature, using ammonium hydroxide as a catalyst. 43 Other work using MPS to prepare hybrid colloids by emulsification also use base catalysis at room temperature. [44][45][46] This step precedes the free-radical polymerization of the unreacted vinyl groups present in the MPS colloid, "solidifying" the particle and creating a polymer-silica hybrid.…”