Syntheses and Properties of Cellulosic Derivatives for Reflection Color Films

Abstract

This report describes the syntheses and properties of cellulosic derivatives for reflection color films. As hydroxypropyl cellulose (HPC) was reacted with acryloyl chloride, we prepared a series of HPC derivatives tethering acryloyl side chains (HPC-Ac) at their different esterification degrees. When the cell of HPC-Ac was heated in a stepwise manner, we observed thermotropic cholesteric liquid crystal (CLC) feature with Bragg reflection in the full-visible wavelength range. Such temperature dependence of Bragg reflection could be controlled by tuning esterification degree of acryloyl side chains of HPC-Ac. We succeeded in the permanent preservation of periodic helical CLC structure by thermo-or photo-induced crosslinking reaction between the acryloyl side chains of HPC-Ac, resulting in fabrication of reflection color films with thermal stability up to 180 C. This report provides promising clues to fabricate the robust multi-colored films, derived from biomass of cellulose, for novel photonic devices.

Viscoelastic Properties of Cholesteric Liquid Crystals from Hydroxypropyl Cellulose Derivatives

“…The rheological behavior of HPC derivatives possessing acyl groups is interesting. Previous studies reported that sticky products are obtained by acylation of HPC [3,4,[8][9][10]. This phenomenon is quite strange in that sticky polymer melts are produced from a powdery raw material of pristine HPC after the simple acylation.…”

“…This phenomenon is quite strange in that sticky polymer melts are produced from a powdery raw material of pristine HPC after the simple acylation. In addition, the fundamentals and applications of HPC derivatives with acyl groups are numerously discussed, focusing on their environmental-friendliness and CLC properties [10][11][12][13][14][15]. As well as the other CLC materials, it is expected to be applied for versatile photonic devices such as temperature sensors and reflective color displays.…”

Fabrication of Reflective Color Films from Cellulose Derivatives

“…Similarly, the thermally induced shifting behavior of reflection peak was observed for the lyotropic CLC of HPC-AcE (AcE = 0.03) in water. At first glance, it seems that the reflection wavelength shift range upon heating process is wider than those of the previously reported lyotropic and thermotropic CLCs [17][18][19]22]. This is probably because water has a relatively high value of thermal volume expansion coefficient, resulting in widely expanding the molecular helical pitch.…”

“…This situation motivates us to fabricate the reflective color films with low risks to human health as well as environment by using water instead of liquid monomers [19]. Since it is necessary to adopt liquid monomers for the lyotropic CLC mixtures or to use the thermotropic CLCs of crosslinkable cellulose derivatives for the formation of solid-state films by polymerization or crosslinking reaction, our attention has been focused on the crosslinkable HPC derivatives.…”

Side Chain Effect of Hydroxypropyl Cellulose Derivatives on Reflection Properties

“…One of the cellulose derivatives, hydroxypropyl cellulose (HPC), is known to exhibit thermotropic CLC phase with visible Bragg reflection by appropriate chemical modification of the side chains [5,6,7,8,9]. In previous reports on the optical properties of cellulose derivatives, the reflection wavelength was controlled by changing the side chain length and modification rates in the thermotropic CLCs, and concentrations in the lyotropic CLCs [10,11,12,13,14,15,16,17,18,19]. While most of them have one or two linear alkyl groups in the side chains, very few studies have reported on the CLCs from the derivatives that possess bulky substituents such as phenyl groups [20].…”