Scientists prepare a new type of liquid crystal elastomer, greatly reducing the

2024-05-04

Recently, Professor Guo Jinbao and his team from Beijing University of Chemical Technology have developed a multifunctional liquid crystal elastomer that possesses intrinsic luminescence, self-healing, and shape memory properties.

The network structure of this elastomer uses imine-based dynamic covalent bonds, which can form conformations that aggregate and dissociate within the material, thereby endowing it with a variety of functions.

This allows the elastomer to exhibit excellent optical and mechanical properties, providing new possibilities for the application of liquid crystal elastomers in various fields.

In terms of application prospects, this material can achieve information storage and transmission.

Compared with traditional information recording materials that rely on photoresponsive molecules, cluster luminescent materials do not require complex organic synthesis, thus avoiding environmental pollution and potential threats to human health.At the same time, the information written in has extremely high resolution and stability, which can efficiently realize the storage of information and further apply it in anti-counterfeiting of trademarks, laying the foundation for its application in the fields of display technology and display directions.

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In addition, this material can not only be made into thin films but also into fibers, expanding its application potential in different forms.

Using its reprogramming ability in the process of stretching and twisting, intelligent and self-adaptive shape flexible robots can be designed.

During the process of stretching and twisting, the internal stress is stored through a dynamic cross-linking network. When the environmental temperature changes, the reprogrammed fibers can convert internal energy into regular motion, thus achieving directional movement. It can be seen that this material has a great application potential in the field of soft intelligent robots.

At the same time, this material also has a great application potential in the field of fluorescent textiles. For example, fibers can be custom-woven, and various complex and diverse patterns can be designed.

It is also learned that the uniqueness of this material lies in its self-healing function, which makes the fibers self-healable when they break, without the need for additional sewing.The restored pattern retains its fluorescence and does not break when stretched. Therefore, this material not only can be used for ecologically friendly practical production, but its high degree of customization also enhances user acceptance.

The Difficulty of Balancing the "Optical and Mechanical" Performance of Liquid Crystal Elastomers

Against the backdrop of sustainable development in contemporary society, the development of functionally integrated materials has also been put forward with multiple requirements, including environmental friendliness, resource sustainability, and energy efficiency.

Materials should minimize environmental impact as much as possible, reduce resource consumption and waste production during production, use, and disposal, while also having high-performance capabilities and production processes that meet social responsibility, in order to achieve sustainable impact on the environment and society.Liquid Crystal Elastomers (LCEs), as a new type of smart material, have become significant contributors to sustainable development through improvements in material synthesis technology and the expansion of multifunctionality.

They can achieve efficient use of resources by precisely controlling structure and performance, reducing waste and energy consumption, and can be used in fields such as smart materials and wearable devices, promoting the development of sustainable energy and lifestyles.

In addition, for emerging technologies such as wearable technology, flexible electronic devices, and smart materials, materials with multifunctionality and customizability are needed to realize potential applications.

Therefore, the research on LCEs aims to address the limitations of existing materials in specific applications, while also exploring new structures and properties to meet the growing technological and societal demands.

Among them, LCE materials with photonic properties exhibit tunable and flexible optical behaviors, providing revolutionary approaches for applications ranging from soft actuators, information storage media to optical sensors.However, traditional methods are often accompanied by complex structural design and preparation processes. In addition, the balance and integration of optical performance and mechanical properties have not yet been explored and remain a challenge. Based on this, the team of Guo Jinbao carried out this study.

Unexpected discovery of fluorescent properties

It is reported that the research team initially envisioned developing a new type of liquid crystal elastomer containing dynamic imine bonds on the basis of previous research [1]. However, during the research process, they unexpectedly found that this material has fluorescent properties.

Therefore, before starting to study the mechanical properties and dynamic covalent bond properties of liquid crystal elastomers, they tried to first conduct a detailed investigation of the fluorescent properties of liquid crystal elastomers, including spectral characterization and verification of cluster luminescence.Using the theory of multiple peak analysis for calculation and comparison with experiments, the team further determined the contribution of imines and secondary amines to the fluorescence emission wavelength, thus enabling the preparation of multi-fluorescent color liquid crystal elastomers (LCEs) by controlling the content of different functional groups.

They also established a molecular library on this basis to design new liquid crystal elastomers with cluster luminescence properties.

The mechanical properties of liquid crystal elastomers are of great significance for their practical applications, so they systematically studied the mechanical properties of this material as well as the dynamic network and physicochemical stability of the elastomers.

Firstly, the determination of the stress-strain curve is important because it involves assessing the soft elasticity of the material and its further applications.

Additionally, they confirmed the dynamic network and physicochemical stability of the prepared elastomers through rheological experiments and thermal expansion experiments.Translating the given text into English:

How to put a new material into practical use is also a very important subject.

After fully mastering the performance of this LCE, they began to address how to combine the luminescent function of clusters with the excellent mechanical properties of liquid crystal elastomers.

After setting this goal, they first proposed the theoretical application potential, and spliced multi-module displays with LCEs of different fluorescence colors. This design provides multifunctional devices suitable for display and optoelectronic applications.

In the experimental process, they found that there is a significant difference in the luminescence of LCE clusters before and after polymerization. Based on this property, the research team can fully achieve information writing that does not depend on photosensitive substances, which greatly reduces the production cost of information recording materials.

In addition, considering the multifunctionality of this material, the team happened to come into contact with work related to soft intelligent robots and liquid crystal elastomer fibers at that time, so they immediately started related research.

Note: The translation is done to the best of my ability to maintain the original meaning and context of the text. Some terms may not have a direct English equivalent and are translated based on their context.They found that if it started with just a single fiber, its movement was chaotic and unorganized. Therefore, based on this, they twisted and bent a single fiber to form a double-stranded fiber, thereby obtaining a soft robot capable of directional movement.

Finally, they returned to the most basic use of the fiber and found that this material could be used as a fluorescent fabric, and the dynamic imine bond could also endow the fabric with self-healing capabilities.

The phenomenon of fluorescence, in fact, was an unexpected discovery in this study. In the past, to achieve luminescence, it was necessary to incorporate traditional fluorescent molecules with large conjugated structures.

However, in the material system of this team, there is no such structure, so they were very excited when they discovered this phenomenon.

That is to say, the material in this study can not only achieve luminescence but also avoid a large amount of organic synthesis, saving a lot of resources.However, at that time, they did not have a sufficient understanding of cluster luminescence. Therefore, after extensive literature review and experimental verification, the research team finally clarified the mechanism of this unconventional luminescence and carried out extension and expansion.

"In this way, we used an unexpected discovery as a prelude and revealed its intrinsic mechanism in detail. In the end, we were able to truly apply it to daily life. This process is infinitely memorable," said Guo Jinbao.

Ultimately, the relevant paper was published in Advanced Materials[2] with the title "Cluster-Triggered Self-Luminescence, Rapid Self-Healing, and Adaptive Reprogramming Liquid Crystal Elastomers Enabled by Dynamic Imine Bond."

Qingyan Fan is the first author, and Guo Jinbao serves as the corresponding author.

Subsequently, they will focus on improving the following aspects:Firstly, the enhancement of stability and durability.

 

Improve the stability and durability of cluster luminescent liquid crystal elastomers, extend their service life, and maintain stable performance under various environmental conditions.

 

Secondly, the improvement of the preparation process.

 

Optimize the preparation process, improve production efficiency, reduce costs, and achieve large-scale production to promote the commercial application of cluster luminescent liquid crystal elastomer technology.

 

Thirdly, the expansion of application fields.

 Explore the broader applications of cluster luminescent liquid crystal elastomers in fields such as virtual reality, augmented reality, wearable devices, flexible displays, and lighting, to promote the development of their technology and market.

At the same time, they plan to use machine learning technology to screen and construct molecular libraries, thereby further reducing the cycle and cost of personalized material development.

It is hoped that the performance and application range of cluster luminescent liquid crystal elastomers can be continuously improved to meet the growing market demand and technical challenges, promote their extensive application in electronic display, lighting and other fields, and promote the development and innovation of liquid crystal technology and luminescent materials.

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