Designing Supramolecular Gelators: Challenges, Frustrations, and Hopes

Abstract

This article is a personal account of the author, who serendipitously entered the field of supramolecular gels nearly two decades ago. A supramolecular synthon approach in the context of crystal engineering was utilized to develop a working hypothesis to design supramolecular gelators derived from simple organic salts. The activity not only provided a way to occasionally predict gelation, but also afforded clear understanding of the structural landscape of such supramolecular materials. Without waiting for an ab initio approach for designing a gel, a large number of supramolecular gelators derived from organic salts were designed following the working hypothesis thus developed. Organic salts possess a number of advantages in terms of their ease of synthesis, purification, high yield and stability and, therefore, are suitable for developing materials for various applications. Organic salt-based gel materials for containing oil spills, synthesizing inorganic nanostructures and metal nanoparticles, sensing hazardous gas and dissolved glucose, adsorbing dyes, and facilitating drug delivery in self-delivery fashion have been developed. The journey through the soft world of gelators which was started merely by serendipity turned out to be rewarding, despite the challenges and frustrations in the field.

Low Molecular Weight Gelators Based on Functionalized l-Dopa Promote Organogels Formation

“…A recent study on the possibility of developing a general road map to an ab initio design of a gelator or a gel, has demonstrated that is not possible to achieve such a goal, as more molecular-level insights into the self-assembly process leading to gelation are required [19,30,31].…”

Stimuli responsive dynamic transformations in supramolecular gels

“…[306][307][308] Generally, the binding sites are connected to some associating units on the gelator structure that assist self-assembly involving non-covalent interactions. 18,[309][310][311] Such associating units may contain hydrophobic moieties like cholesterol 169,[312][313][314] and aromatic surface, 315 or hydrophilic functionalities like peptide, 316 sugar 317 etc. Chemical analyte responsive gels have huge potential as molecular sensors, aggregation probes, antibacterial agents, conducting materials and water purifying agents.…”

Programming properties of transient hydrogels by an enzymatic reaction

“…Supramolecular gels are formed when monomeric building blocks self-assemble into long fibrous structures that entrap solvent molecules. [1][2][3][4][5][6][7] Generally, man-made selfassembly is an energetically down-hill process and so selfassembled gels can be formed under thermodynamic equilibrium. [8][9][10][11] However, depending on the preparative pathway, self-assembled gels may exist as kinetically trapped structures where the assembly structures reside in the local thermodynamic minimum in the free energy landscape.…”