China
Africa
Explore chapters and articles related to this topic
Materials, Chemistry, and Synthesis of Covalent Organic Frameworks
Published in Tuan Anh Nguyen, Ram K. Gupta, Covalent Organic Frameworks, 2023
Mohaddeseh Afshari, Mohammad Dinari
COFs are a new class of porous polymers in which small organic building blocks are precisely integrated into extended structures with periodic skeletons and regular pores [4]. During the formation of networked covalent structures, unlike zero-dimensional and one-dimensional organic structures, several frameworks with different free energies may be created; as a result, it seems complicated to achieve a crystalline and perfectly regular structure. The chemical reaction process is always like a swing between the kinetic and thermodynamic equilibria. Over recent years, a new concept called dynamic covalent chemistry (DCC) has been introduced in which reversible chemical reactions are performed under thermodynamic control [5, 6]. The reversible nature of the reactions allows error checking and proof-reading in the generated covalent structure to obtain the thermodynamic product with the lowest free energy and convenient crystallinity (Figure 2.1) [7]. The point to note is the high energy of covalent bonds (50−110 kcal mol−1), so to achieve a thermodynamic product, the reactions must be performed at high temperature and pressure conditions.
Recent progress in self-healable ion gels
Published in Science and Technology of Advanced Materials, 2020
Ryota Tamate, Masayoshi Watanabe
Ion gels are a new class of soft material that offer unique physicochemical properties inherent to ILs; hence, they are promising for use in diverse electrochemical applications. In this article, we overviewed recent progress on functional ion gels that can heal mechanical damage through application of an external stimulus or in an autonomous fashion. Photo-healing is a very attractive strategy due to the non-invasiveness and high spatiotemporal controllability of light. In addition, thermally healable ion gels that take advantage of the high thermal stability, non-volatility, and non-flammability of ILs have been developed. Furthermore, based on supramolecular chemistry and dynamic covalent chemistry, the number of reports of self-healing ion gels that do not require external stimuli have gradually increased. Through the precise design of polymer architectures that exploit interactions between the polymer and the IL, ion gels with self-healing abilities as well as other functionalities, such as high stretchability and toughness, can be created. Despite these successes, whether or not the self-healing functions of ion gels can truly contribute to high durability against mechanical loads under the practical conditions that wearable/stretchable devices are expected to operate in remains unclear. Furthermore, as with other self-healing materials, improving creep behavior is another difficult challenge for self-healing ion gels that are reversibly crosslinked [108]. Insightful understanding and control of the complicated interactions between cations, anions, and polymers is critical for future development and for realizing self-healing ion gels that overcome the hurdles presently faced for practical applications.