Topological Transition in Spontaneously Formed Cellulosic Liquid-Crystalline Microspheres in a w/o Emulsion

Abstract

A cholesteric liquid crystal (ChLC) in a confined space has attracted significant scientific interest and has potential applications. ChLC microspheres have been obtained by devising processing such as a microfluidic technique. Herein, we adopted the self-assembly approach for the spontaneous formation of cellulosic ChLC microspheres. A functional block copolymer (BCP) was grafted to hydroxypropyl cellulose (HPC), making it amphiphilic to self-assembly in a w/o emulsion. The HPC segment aggregated in the aqueous phase under lyotropic conditions and produced the ChLC microspheres dispersed in the oil phase. The microspheres exhibited a topological transition between radial and bipolar while altering the molecular structure in terms of the molecular weight of BCP and the degree of substitution of HPC. The coexistence of inorganic salts in the aqueous HPC lyotropic phase changed the mesophase behavior as well. Such cellulosic ChLC microspheres will present opportunities to develop biobased optical devices and stimuli-responsive biomedical materials.

Injectable Microfluidic Hydrogel Microspheres for Cell and Drug Delivery

“…[ 20 ] Furthermore, the size of the microspheres prepared by the emulsion method is usually uneven, which can lead to problems for downstream applications that require a strict size distribution. [ 21 ] Therefore, to overcome these defects, microfluidic technology has recently been used to tailor microspheres.…”

Progress in the Application of Food-Grade Emulsions

“…Cellulose-based liquid crystal microspheres can be formed by self-assembly in water-in-oil emulsions. The topological transition between the radial and bipolar forms of these microspheres is expected to provide biomedical materials for the development of stimuli-responsive bio-optical devices [ 324 ]. In addition, the Pickering emulsion template method can control the surface wettability properties of polymer microspheres and superhydrophobic surfaces, while super-oleophilic surfaces can be formed on polymer microspheres by means of the Pickering emulsion polymerization method [ 325 ].…”

Construction of Functional Materials in Various Material Forms from Cellulosic Cholesteric Liquid Crystals

“…Chakrabarty et al [106] prepared cellulose derivative-based ChLC emulsions from a cellulose derivative-g-block copolymer (BCP) without using a microfluidic technique or adding external surfactants. In this system, the grafted BCP-side chains underwent self-assembly in a water/oil mixture because of their amphiphilicity, resulting in ChLC emulsions containing microdroplets with an inside cellulose derivative-based ChLC solution and an outside BCP layer.…”

“…The researchers evaluated the relationships between the chemical structure of cellulose derivative-g-BCP and the physical properties of the ChLC microdroplets. Chakrabarty et al [106] synthesized a series of BCPs composed of hydrophilic poly (oligoethylene glycol methacrylate-co-glycidyl methacrylate) and hydrophobic polystyrene blocks by reversible addition-fragmentation chain transfer polymerization. They varied the ratio for the degree of polymerization of the hydrophilic and hydrophobic blocks (x) by changing the polystyrene block length.…”

“…To examine the effect of adding salt to the ChLC emulsions, Chakrabarty et al [106] prepared emulsions from HPC-g-(BCP-6.7) 0.006 with LiSCN aqueous solutions at various concentrations as the water-based phase. CD spectroscopy of the ChLC emulsions with LiSCN indicated that increasing the concentration of LiSCN gave rise to a broadened CD peak of the emulsions (Figure 12h), which differed from the systematic blue-shift observed in the simple HPC aqueous solution system described in Section 3.1.…”