Light-induced liquid crystallinity.

Area of Science:

• Materials Science
• Physical Chemistry
• Optics

Background:

• Liquid crystals are classified by their response to stimuli like heat (thermotropic) or solvents (lyotropic).
• Photoresponsive liquid crystals typically decrease in order upon light exposure, undergoing isothermal phase transitions.
• Previous studies observed light-induced order decrease, with rare exceptions of order increase under specific conditions.

Purpose of the Study:

• To report a novel class of naphthopyran-based liquid crystals.
• To demonstrate photo-induced order-increasing phase transitions in these materials.
• To explore the potential applications of these order-increasing photoresponsive liquid crystals.

Main Methods:

• Synthesis and functionalization of naphthopyran molecules.
• Investigation of photo-induced conformational changes and their effect on molecular structure.
• Characterization of phase transitions and order parameter changes upon light exposure.

Main Results:

• Naphthopyran materials exhibit photo-induced conformational changes leading to order-increasing phase transitions.
• The open form of functionalized naphthopyran molecules shows a large order parameter.
• A clear-to-absorbing dichroic state transition was observed upon light exposure.

Conclusions:

• This research introduces naphthopyran-based liquid crystals capable of light-induced order increase.
• The observed phenomenon has significant potential for applications in optics, photonics, lasing, displays, and solar energy harvesting.
• The large photo-induced dichroism is promising for ophthalmic applications like photochromic sunglasses.