Stimuli-responsive hydroxyapatite liquid crystal with macroscopically controllable ordering and magneto-optical functions

Masanari Nakayama,Akihito Kumamoto,Masafumi Yamato,Yuichi Ikuhara,Tatsuya Nishimura,Takashi Kato,Satoshi Kajiyama

doi:10.1038/s41467-018-02932-7

Masanari Nakayama, Akihito Kumamoto + Show 5 more

Open Access

https://doi.org/10.1038/s41467-018-02932-7

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Abstract

Liquid crystals are mostly formed by self-assembly of organic molecules. In contrast, inorganic materials available as liquid crystals are limited. Here we report the development of liquid-crystalline (LC) hydroxyapatite (HAp), which is an environmentally friendly and biocompatible biomineral. Its alignment behavior, magneto-optical properties, and atomic-scale structures are described. We successfully induce LC properties into aqueous colloidal dispersions of rod-shaped HAp by controlling the morphology of the material using acidic macromolecules. These LC HAp nanorod materials are macroscopically oriented in response to external magnetic fields and mechanical forces. We achieve magnetic modulation of the optical transmission by dynamic control of the LC order. Atomic-scale observations using transmission electron microscopy show the self-organized inorganic/organic hybrid structures of mesogenic nanorods. HAp liquid crystals have potential as bio-friendly functional materials because of their facile preparation, the bio-friendliness of HAp, and the stimuli-responsive properties of these colloidal ordered fluids.

Highlights

Liquid crystals are mostly formed by self-assembly of organic molecules
We explore the use of acidic macromolecules to synthesize mesogenic HAp nanorods capable of forming colloidal liquid crystals (Fig. 1a–c)
The arched pattern observed in the selected-area electron diffraction (SAED) pattern (Fig. 2b) shows that the polycrystal have the preferred orientation along with the a Supersaturated aqueous solution

Summary

Introduction

Liquid crystals are mostly formed by self-assembly of organic molecules. In contrast, inorganic materials available as liquid crystals are limited. We successfully induce LC properties into aqueous colloidal dispersions of rod-shaped HAp by controlling the morphology of the material using acidic macromolecules These LC HAp nanorod materials are macroscopically oriented in response to external magnetic fields and mechanical forces. Liquid crystals form fluid but ordered molecular assemblies[1,2,3], and these self-assembled structures can be dynamically controlled by application of external stimuli such as electric and magnetic fields, and mechanical forces, leading to various functions[4,5,6,7,8,9,10,11]. LC HAp, the use of magnetic fields could be promising for orientational control because self-assembly into LC ordered fluids can promote magnetic alignment[36,37,38]

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