Issue 45, 2018

Thermal and electrical wavelength tuning of Bragg reflection with ultraviolet light absorbers in polymer-stabilized cholesteric liquid crystals

Abstract

Autonomous stimulus-responsive polymer-stabilized cholesteric liquid crystals (PSCLCs) are promising materials for various applications. In this work, a PSCLC cell whose wavelength of selective reflection changes autonomously according to the temperature or can be controlled by applying an electric field was fabricated by using ultraviolet (UV) light absorbers. The UV light absorbers in the PSCLC cell are used not only for preventing the degradation of the substrate but also for stabilizing the polymeric network by converting the harmful UV radiation into harmless heat. To achieve the optimum conditions, different types of UV light absorbers were examined at various concentrations and UV light intensities. The results revealed that the benzophenone-type UV absorbers provide an extensive blue-shift tuning of the Bragg reflection in the PSCLC. By determining the molar extinction coefficient (ε) values, which provide a measure of UV light absorption at a given wavelength, at three important wavelengths—the maximum absorption wavelength (λmax) of the UV absorbers, λmax of the photoinitiator (345 nm), and the UV lamp wavelength (365 nm)—the UV light intensity gradient throughout the cell was defined. Reduction of the ε value indicates a sharp drop in the UV light intensity within a PSCLC cell. This phenomenon leads to the diffusion of reactive mesogens towards the UV lamp side of the cell to achieve a tight pitch gradient and extensive blue-shift tuning of the selective reflection.

Graphical abstract: Thermal and electrical wavelength tuning of Bragg reflection with ultraviolet light absorbers in polymer-stabilized cholesteric liquid crystals

Supplementary files

Article information

Article type
Paper
Submitted
10 Sep 2018
Accepted
18 Oct 2018
First published
19 Oct 2018

J. Mater. Chem. C, 2018,6, 12377-12385

Thermal and electrical wavelength tuning of Bragg reflection with ultraviolet light absorbers in polymer-stabilized cholesteric liquid crystals

A. Ranjkesh and T. Yoon, J. Mater. Chem. C, 2018, 6, 12377 DOI: 10.1039/C8TC04563A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements