Large Thermally Irreversible Photoinduced Shift of Selective Light Reflection in Hydrazone-Containing Cholesteric...

Area of Science:

• Materials Science
• Polymer Chemistry
• Photonics

Background:

• Stimuli-responsive liquid crystalline polymers (LCPs) are "smart" materials with controllable mesomorphic structures.
• External fields, particularly light, can precisely tune LCP properties.
• Photochromic materials offer potential for light-induced property changes.

Purpose of the Study:

• To synthesize and investigate a novel comb-shaped hydrazone-containing copolyacrylate.
• To explore its cholesteric liquid crystalline properties and light-induced tunability.
• To assess the impact of doping on photo-optical response and thermal stability.

Main Methods:

• Synthesis of a hydrazone-containing copolyacrylate.
• Characterization of cholesteric liquid crystalline phase and helical pitch.
• Measurement of selective light reflection spectra under blue light irradiation.
• Evaluation of photo-optical response and thermal stability of isomers.

Main Results:

• The synthesized copolyacrylate exhibits cholesteric liquid crystalline properties.
• A significant blue shift in selective light reflection (1650 nm to 500 nm) was observed under blue light (428/457 nm) irradiation.
• This photoinduced shift is attributed to reversible Z-E isomerization of photochromic hydrazone groups.
• Doping with low-molar-mass liquid crystal enhanced the photo-optical response speed.
• Both E and Z isomers demonstrate thermal stability, enabling dark-relaxation-free switching.

Conclusions:

• The hydrazone-containing copolyacrylate exhibits tunable cholesteric liquid crystalline properties via light irradiation.
• The material demonstrates a large, reversible photoinduced shift in selective light reflection.
• Thermal bistability and enhanced photo-optical response suggest potential applications in photonics.