Advances in Thermochromic Liquid Crystals and Functional Colour-Changing Materials

Dear Colleagues,

Thermochromic liquid crystals (TLCs) stand out due to their unique ability to change colour in response to temperature fluctuations, a property that arises from their liquid–crystalline phases. This remarkable combination of thermal sensitivity and optical responsiveness has led to their application in various fields, from temperature mapping and medical diagnostics to smart packaging and security. However, there are many other dynamic, colour-changing materials with the potential to be employed in various technologies. This Special Issue focuses on the utilization of TLCs and other functional colour-changing systems, such as leuco dyes, photochromic, piezochromic, and electrochromic materials. These systems, while differing in their stimulus (e.g., heat, light, pressure, or electric fields), all use molecular or crystalline structures that enable reversible colour changes. By investigating the functional behaviours of these diverse materials, this Special Issue aims to address the application of thermally responsive TLCs and broader classes of colorimetric materials.

The scope of the Special Issue includes, but is not limited to, the following topics:

• Thermochromic liquid crystals—the development of new TLC formulations, including hybrid systems that enhance temperature sensitivity and durability across different substrates, such as fibre-based and bio-based materials.
• Leuco dyes—exploring their reversible and/or irreversible colour-changing behaviour, with potential applications in security printing and temperature indicators.
• Photochromic and electrochromic systems—investigating their use in dynamic displays, smart packaging, and light-sensitive technologies.
• Piezochromic materials—studying pressure-induced colour changes for use in sensors and wearable devices.

The research of these materials and their interactions could provide the basis for flexible, lightweight, and customizable applications in smart packaging, temperature-sensitive labels, medical diagnostics, and intelligent textiles. The ability to create dynamic visual feedback based on environmental stimuli makes these materials particularly valuable for sustainable design and energy-efficient systems.

We therefore also welcome submissions that address the following topics:

• The formulation, rheological behaviour, and printability of TLCs and related functional inks.
• The application of TLCs in smart packaging, temperature sensors, and security features.
• Advances in leuco dyes, photochromic, piezochromic, and electrochromic materials.
• The role of crystalline and molecular structures in enabling colour-changing effects.
• Industrial challenges in scaling these materials for practical applications.

Dr. Maja Strižić Jakovljević
Dr. Stephen J. Cowling
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• thermochromic liquid crystals (TLCS)
• leuco dyes
• functional colour-changing materials
• photochromic systems
• electrochromic systems
• piezochromic materials
• smart packaging
• temperature sensors
• sensing technologies
• responsive materials
• optical properties