Anisotropic Polymer Particles Research Articles

Miniaturization of anisotropic composite particles incorporating a silica particle smaller than 100 nm

Two-step aqueous polymerizations with a water-soluble initiator of potassium persulfate were conducted to prepare anisotropic composite particles incorporating a silica core smaller than 100 nm. The two-step polymerization consisted of the first polymerization to coat the silica cores with cross-linked polymethylmethacrylate (PMMA) shell and the second polymerization to protrude a polystyrene (PSt) bulge from the core–shell particles. The concentration of ionic comonomer of sodium p-styrenesulfonate (NaSS) in the first polymerization was an important factor to stabilize the core–shell particles during the second polymerization as well as the first one, and an appropriate concentration of NaSS could prepare the anisotropic composite particles incorporating a single core. Another important factor for small, anisotropic composite particles was duration time for swelling the core–shell particles with the second monomer of styrene. Extension of the duration time from 2 to 4 h facilitated protrusion of the PSt bulge from the particles incorporating a 44-nm silica core. The composite particles were also employed to fabricate anisotropic hollow particles. Chemical etching of silica component in the composite particles with hydrofluoric acid successfully created anisotropic hollow polymer particles with a cavity size corresponding to the silica cores.

Controlled Synthesis of Anisotropic Polymer Particles Templated by Porous Coordination Polymers

Nonspherical polymer particles have been efficiently prepared in different morphological crystals of porous coordination polymers (PCPs) by in situ radical polymerization of styrene and methylmethacrylate, followed by removal of the host PCP frameworks in aqueous tetrasodium ethylenediaminetetraacetate (Na-EDTA) solution. In this replication process, the isolated vinyl polymer particles retained the size and morphologies of the original PCP particles, although the polymer chains were not stabilized by cross-linking. This morphological retention of vinyl polymers after the isolation from the PCP matrixes was ensured by the rigidity and porosity of the polymers, which was confirmed by DSC and adsorption measurements. The unconventional assembly of polymer chains in the particles is of interest from the viewpoints of functional properties of the polymer particles.

Compartmentalization of Gold Nanocrystals in Polymer Microparticles using Electrohydrodynamic Co‐Jetting

Polymer particles with micro- and nanoscale anisotropy have received increasing interest for their ability to simultaneously present different physical- and chemical properties. In this communication, we demonstrate that gold nanocrystals (NCs) can be selectively incorporated into one compartment of anisotropic polymer particles. Stable bicompartmental particles were prepared via electrohydrodynamic co-jetting of aqueous nanoparticle suspensions followed by thermal cross-linking. Bicompartmental particle populations with different NC densities were obtained by varying the NC concentration in the jetting suspension. While NC-loaded polymer particles showed different optical properties depending on the NC density, they still maintained discrete interfaces between two compartments. Moreover, the fraction of the bicompartmental particles was higher than 98% based on flow cytometry. This study delineates a new approach for preparation of inorganic/organic composite particles with precisely engineered, anisotropic nanoparticle distributions and may contribute to further developments in emerging scientific areas, such as smart materials or particle-based diagnostics.

Biocompatible Polymers: Structurally Controlled Bio-hybrid Materials Based on Unidirectional Association of Anisotropic Microparticles with Human Endothelial Cells (Adv. Mater. 48/2009).

Biocompatible anisotropic polymer particles with bipolar affinity towards human endothelial cells are a novel type of building blocks for microstructured biohybrid materials, report Joerg Lahann and co-workers on p. 4920. Functional polarity due to two biologically distinct hemispheres has been achieved by synthesis of anisotropic particles via electro-hydrodynamic co-jetting of two different polymer solutions and subsequent selective surface modification.

Structurally Controlled Bio-hybrid Materials Based on Unidirectional Association of Anisotropic Microparticles with Human Endothelial Cells.

Biocompatible anisotropic polymer particles with bipolar affinity towards human endothelial cells are a novel type of building blocks for microstructured bio-hybrid materials. Functional polarity due to two biologically distinct hemispheres has been achieved by synthesis of anisotropic particles via electro-hydrodynamic co-jetting of two different polymer solutions and subsequent selective surface modification.

Fabrication of Monodisperse Toroidal Particles by Polymer Solidification in Microfluidics

Microdoughnuts: Polymer toroidal particles such as the one shown in the left picture have been prepared by a capillary microfluidic technique. Droplets of polymer solution undergo non-uniform solidification to form the anisotropic polymer particles. By incorporating functional materials inside the polymer network, functional toroidal particles (center and right images) can be tailor-made for specific applications such as magnetic actuation.

Synthesis of Anisotropic Polymer Particles with Soap‐Free Emulsion Polymerization in the Presence of a Reactive Silane Coupling Agent

AbstractA novel two step method has been developed for the preparation of anisotropic polymer particles using soap‐free emulsion polymerization in the presence of the reactive silane coupling agent 3‐methacryloxypropyltrimethoxysilane (MPTMS). In the first step, seed polymer particles were prepared in the presence of MPTMS in water. In the second step, another polymerization was conducted in the presence of the seed particles, which induced anisotropic protrusion of polymer from the seed particles. The two step method is applicable to the preparation of anisotropic polymer particles containing inorganic particles such as silica. Silica particles inside the anisotropic polymer particles were dissolved with hydrofluoric acid, which created hollow polymer particles with anisotropy.magnified image

Electrically Driven Alignment and Crystallization of Unique Anisotropic Polymer Particles

Micrometer-sized monodisperse anisotropic polymer particles, with disk, rod, fenestrated hexagon (hexnut), and boomerang shapes, were synthesized using the particle replication in nonwetting templates (PRINT) process, and investigations were conducted on aqueous suspensions of these particles when subjected to alternating electric fields. A coplanar electrode configuration, with 1 to 2 mm electrode gaps (20-50 V ac, 0.5-5.0 kHz) was used, and the experiments were monitored with fluorescence microscopy. For all particle suspensions, the field brought about significant changes in the packing and orientation. Extensive particle chaining and packing were observed for the disk, rod, and hexnut suspensions. Because of the size and geometry of the boomerang particles, limited chaining was observed; however, the field triggered a change from random to a more ordered packing arrangement.