Monodisperse Liquid Crystal Network Particles Synthesized via Precipitation Polymerization

Abstract

The production of liquid crystalline (LC) polymer particles with a narrow size distribution on a large scale remains a challenge. Here, we report the preparation of monodisperse, cross-linked liquid crystalline particles via precipitation polymerization. This versatile and scalable method yields polymer particles with a smectic liquid crystal order. Although the LC monomers are randomly dissolved in solution, the oligomers self-align and LC order is induced. For the polymerization, a smectic LC monomer mixture consisting of cross-linkers and benzoic acid hydrogen-bonded dimers is used. The average diameter of the particles increases at higher polymerization temperatures and in better solvents, whereas the monomer and initiator concentration have only minor impact on the particle size. After deprotonating of the benzoic acid groups, the particles show rapid absorption of a common cationic dye, methylene blue. The methylene blue in the particles can be subsequently released with the addition of Ca2+, while monovalent ions fail to trigger the release. These results reveal that precipitation polymerization is an attractive method to prepare functional LC polymer particles of a narrow size distribution and on a large scale.

Flower‐Like Colloidal Particles through Precipitation Polymerization of Redox‐Responsive Liquid Crystals

“…Initial studies were conducted in phenyl acetate at 65 8 8Cb ased on our earlier results using as imilar LC monomer mixture containing ad ifferent cross-linker,v ide supra. [45] Ther esulting polymer particles were flower-like,w ith "petal" moieties on the surfaces (Figure 1b and c). Thea verage diameter of the particles was % 750 nm, with acoefficient of variation (CV) of 7.2 %and an average circularity of 0.59.…”

“…Since previous publications indicated that the polymerization conditions,i ncluding the solvent and polymerization temperature,m ay have profound influence on particle morphologies,L Cp olymer particles were prepared using aseries of solvent mixtures and polymerization temperatures to reveal the impact of these conditions. [45,47]…”

“…[44] Previously,w er eported on the preparation of spherical polymer particles via precipitation polymerization of asmectic al iquid crystalline (LC) monomer mixture consisting of across-linker and benzoic acid hydrogen-bonded dimers. [45] In this paper,w er eport the preparation of monodisperse, "flower-like" particles via precipitation polymerization of aLCmonomer mixture.The monomer mixture consists of the same benzoic acid-functionalized acrylates as used before but the cross-linker is replaced by ar edox-responsive disulfidefunctionalized diacrylate.I ti sfound that the introduction of aminor fraction of the disulfide-functionalized diacrylates ( 10 wt %) induces the formation of af lower-like morphology. Theshape of these particles can be tuned from flower-like to spherical simply by elevating the polymerization temperature, while the solvent itself mainly influences the particle size.The flower-like morphology already forms during the early stages of the polymerization, after which particle growth occurs.…”

Liquid‐Crystalline Polymer Particles Prepared by Classical Polymerization Techniques

“…[ 57 , 58 , 59 , 60 ] LC polymer particles have been successfully prepared by precipitation polymerization of an LC monomer mixture consisting of benzoic‐acid functionalized acrylates and LC diacrylates (Figure 12 a). [61] The particle diameters were between 0.6 and 1.4 μm, mainly affected by the solvent and polymerization temperature. The polydispersity is lower than the similar particles preapred by suspension polymerization (Figure 6 ).…”

“… [28] However, the control of alignment and preparation of non‐radial LC polymer particles by precipitation polymerization have not yet been reported. [61] …”