A Printable Optical Time‐Temperature Integrator Based on Shape Memory in a Chiral Nematic Polymer Network

Abstract

An optical and irreversible temperature sensor (e.g., a time-temperature integrator) is reported based on a mechanically embossed chiral-nematic polymer network. The polymer consists of a chemical and a physical (hydrogenbonded) network and has a refl ection band in the visible wavelength range. The sensors are produced by mechanical embossing at elevated temperatures. A relative large compressive deformation (up to 10%) is obtained inducing a shift to shorter wavelength of the refl ection band ( > 30 nm). After embossing, a temperature sensor is obtained that exhibits an irreversible optical response. A permanent color shift to longer wavelengths (red) is observed upon heating of the polymer material to temperatures above the glass transition temperature. It is illustrated that the observed permanent color shift is related to shape memory in the polymer material. The fi lms can be printed on a foil, thus showing that these sensors are potentially interesting as time-temperature integrators for applications in food and pharmaceutical products.

Chiral-nematic liquid crystals as one dimensional photonic materials in optical sensors

“…At t ¼ 0 s, the sensor had reached the temperature set point, l r is the wavelength of the SRB after heating the sample to 60 C leading to recovery of the original SRB band. Adapted from Davies et al 30 Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. oxygen, amines, humidity and others also play an important role.…”

“…30 CLC network lms were prepared either by a bar-coating process or inkjet printing. Aer photo-polymerization the lms were mechanically embossed above the glass transition temperature (T g ¼ 60 C) using a rigid sphere stamp (Fig.…”

Stimuli-responsive photonic polymer coatings

“…85 Self-assembled hydrogen-bonded CLC polymers result in coatings which respond to temperature changes 86 and can be used as thermally addressable reflective colour paper. An image (the letter ''T'') can be written clearly using a hot pen (Fig.…”

Thermally and Optically Fixable Shape Memory in Azobenzene-Functionalized Glassy Liquid Crystalline Polymer Networks

“…To date, the response of LCN materials to stimuli has primarily been elastic in nature (e.g., in the absence of the stimulus the material restores to the original shape). A few recent publications have examined shape memory in LCN materials [2,[44][45][46][47]. This work employs LCN materials in the twisted nematic orientation.…”