Molecular engineering to develop Li+-enriched conductive metallohydrogels for electronic and electrochemical applications

Abstract

In our everyday life, we use various gel materials including toothpaste, shampoo, hair gel, gel-incorporated capsules, ointments, soft contact lenses, etc [1–3]. Gels can be recognized as solid-like soft materials having broad applications ranging from our daily need products to the advanced technological applications in every branch of science and engineering for the development of soft robotics, soft materials-based electronic devices, soft tissues, gel electrolyte, superabsorbent soft materials, soft actuators and sensors [4]. Gels are the combination of liquid and solid components, in which very small amount (1-10%) of the solid compound known as gelator molecules self-assembled to form crosslinked fibrous network as 3D matrix to entrap the large amount (90-99%) of solvent or liquid molecules making them immobile thereby entire mass appears as solid, as can be seen in Figure 1 [1,4]. As per IUPAC, gel is defined as ‘‘a colloidal network that is expanded throughout its whole volume by a fluid.’’ [5]. The formation of gels can take place in water, organic solvents and ionic liquids thus based on the solvent they can be termed as hydrogels, organogels and ionogels, respectively [4,6]. Since the gel phase is a perfect balance between solution and crystallization therefore not every molecule is suitable as gelator to form gel [7]. In other words, adapting strategic molecular engineering of gelator molecules is essential in order to obtain gel. Molecules can interact with solvents in mainly three ways: In the first case, solvent and molecules interaction results in a highly ordered system leading to the formation of crystals. In the second case, random aggregation of molecules in solvent resulting in the amorphous precipitate.