Research Projects

Synthesis of higher order nanostructures of -conjugated systems is extremely and is vital for their technological applications. Though living supramolecular polymerization (LSP) permits the crafting of 1D supramolecular polymers with remarkable properties, it is extremely challenging to craft higher order nanostructures using LSP. Secondary nucleation, a surface-catalysed process, where the surface of existing aggregate acts as a template and catalyses the assembly of new monomers, has recently been emerged as a potential tool for the crafting of higher order supramolecular polymers. Recent years have witnessed the emergence of a few interesting examples for the synthesis of complex 3D and hetero nanostructures of pi-conjugated molecules by exploring the concept of secondary nucleation. These reports revealed that the secondary nucleation was observed in primary aggregates having non-covalent functional groups on their surface that can interact with the free monomers in solution. Moreover, supramolecular polymerization involving secondary nucleation was observed mostly in nonpolar solvents and rarely demonstrated in aqueous medium. Watson-Crick base pairing interaction of nucleobases (A, G, C and T) are responsible for the duplex structure of DNA and has been widely used for the crafting of different types of nanomaterials. Our group has been extensively working in the area of amphiphilic systems derived from DNA and nucleosides. In this proposal, we envision that nucleoside modified chromophores would be a unique building block to study the secondary nucleation in the supramolecular polymerization of -conjugated systems in aqueous medium. Though the self-assembly of nucleoside modified chromophores was investigated by several research groups across the globe including us, their potential to act as template to trigger/catalyse the secondary nucleation in the supramolecular polymerization has not yet been studied. Herein, we propose the synthesis of a series of nucleoside-chromophore chiral amphiphiles, wherein the nucleoside segment act as a hydrophilic unit whereas the chromophoric part act as the hydrophobic unit. Self-assembly of the amphiphile in aqueous medium results in the formation of chiral primary aggregates with the hydrophilic nucleoside expressed on its surface with the hydrophobic chromophore unit buried inside. The most unique feature of the primary aggregates is its surface decoration with nucleobases, which permits strong hydrogen bonding interaction with the free monomers present in the solution and catalyses secondary nucleation-triggered polymerization. The primary aggregates can also have strong H-bonding interaction with the complementary nucleobase modified chromophore, which permits the hetero secondary nucleation on the surface of the primary aggregates, which is otherwise extremely difficult to achieve in a predictable manner. Our proposal is remarkable in many ways which include (i) a unique nucleoside-modified chromophoric system as a novel class of building block to study the phenomenon of secondary nucleation, (ii) permits the study of secondary nucleation in aqueous medium, which is extremely difficult to achieve, and hence will be an ideal model system to get better insight into the mechanism secondary nucleation of aggregation of amyloid fibrils. This will shed more light for the development of therapeutic agents for various neurodegenerative diseases, (iii) permit the crafting of hetero chromophore nano-assemblies via hetero secondary nucleation and (v) offer a strategy for the synthesis of higher order chiral nanostructures. Most importantly, supramolecular polymerization involving secondary nucleation in most of the cases were observed by serendipity, and hence if successful our approach will provide a universal design strategy to trigger secondary nucleation in water for the synthesis of higher order chiral nanostructures reminiscent of biological systems.