Modifications of FLC Physical Properties through Doping with Fe2O3 Nanoparticles (Part I).

Shin-Ichi Ohkoshi,Monika Marzec,Olaf Stefańczyk,Dorota Dardas,Natalia Górska,Sebastian Lalik

doi:10.3390/ma14164722

Abstract

The aim of this paper is to show, by systematic studies, the influence of γ-Fe2O3 nanoparticles on the physical parameters of the liquid crystalline matrix, exhibiting a ferroelectric phase in a wide temperature range. The detailed research was carried out by using diffraction (PXRD), microscopic (OM, SEM, FCPM, POM), thermal (DSC), optical (TLI), electric and spectroscopic (FTIR) methods. We show that even the smallest concentration of γ-Fe2O3 nanoparticles largely modifies the parameters of the ferroelectric SmC* phase, such as spontaneous polarization, switching time, tilt angle, rotational viscosity, dispersion anchoring energy coefficient and helix pitch. The admixture also causes a significant reduction in the temperature of phase transitions, broadening the SmA* phase at the expense of the SmC* phase and strong streaking of the texture. We present and explain the non-monotonic modification of these parameters with an increase in the nanoparticle concentration. The influence of oleic acid admixture on these parameters is also widely discussed. We have shown that certain parameters of organic-metal nanocomposites can be controlled by the appropriate amount of metal admixture.

Highlights

The experimental setup including the above-mentioned microscope consisted of the 33120A Agilent generator, the F20-FLC Electronics amplifier, the DSO6102A Agilent oscilloscope and the INSTEC PD02 photo-detector, and a system of tunable resistors (a 100 kΩ resistor was used in each case) was used for electric and electro-optic measurements
For all hybrid materials containing EHPDB liquid crystal matrix and Fe2 O3 nanoparticles (Composites 2–6), the diffraction patterns are similar to pure EHPDB (Composite 1), supmainly of maghemite (γ-Fe2O3), very small impurities of hematite (α-Fe2O3) and magnetite (Fe3O4), by-products in the preparation of maghemite, may occur
Diffraction patterns of Composites 1–6 and Sample 1 are shown in Figure8 of all hybrid materials containing EHPDB liquid crystal matrix and Fe2O3 nanoparticles (Composites 2–6), the diffraction patterns are similar to pure EHPDB (Composite 1), supplemented withlow-intensity low-intensity peaks peaks characteristic maghemite, the the intensity of which plemented with characteristicofof maghemite, intensity of which increases withincreasing increasing Fe confirming the presence of both components increases with concentration, confirming the presence of both compo2O

Summary

Introduction

New branches have emerged, e.g., involving organometallic materials. This group of materials is divided into two classes: (1) with and (2) without the presence of a chemical bond between a metal atom and an organic ligand. The abovementioned classes of hybrid materials are one of the ways to meet the growing demand for specialized materials. Another way is the chemical synthesis of extremely complex organic materials, including the use of longer alkyl substituents, increasing the number of benzene rings in a rigid core and the presence of heteroatoms (such as S, N) [1,2,3,4]

Objectives

Methods

Results

Conclusion