1) Bioinspired Strategies for Controlling the Hierarchical Supramolecular Architectures:
Biological systems host complex adaptive networks with precise Spatio-temporal control, coupled with sophisticated functionality. In the recent past, our group has made significant inroads towards elucidating the synthetic strategies for the realization of these concepts in materials. Extracting the gist of out-of-equilibrium, fuel-driven networks from the biological world, chemical fuel-driven supramolecular polymerization strategies pioneered in our research laboratory have notably advanced the frontiers of constructing controllable and adaptive materials with mono-disperse structure and predictive sequences. The following are some of the strategies used by us towards achieving adaptive, autonomous, and like-life out-of-equilibrium supramolecular materials.
1A) ATP-fuelled, enzymatically Controlled Approach:
Inspired from Actin protein assemblies, which shows controlled polymerization in response to adenosine triphosphate (ATP) fuel via nucleation-elongation process in a temporal manner to regulate mechanical stability of cell, we have introduced ATP selective and ATP-fuelled synthetic strategies to controlled supramolecular polymerization of a phosphate receptor functionalized monomer (dormant monomer). Here, the system undergoes fuel-driven nucleation and seeded growth that provide length control and narrow dispersity of the resultant assemblies. We present a bioinspired, reaction-coupled approach for the controlled supramolecular polymerization in synthetic systems. Using an enzymatic reaction that interfaces with the adenosine triphosphate (ATP)-templated supramolecular polymerization of naphthalene diimide monomers (NSG) and facilitates reaction-controlled, cooperative growth of the monomers. This growth process, in turn, provides positive feedback to the enzymatic production of ATP, creating an ideal reaction-coupled assembly process. Also, we demonstrated a seed-induced supramolecular polymerization approach for modulating the chiral asymmetry of a supramolecular polymer under kinetic conditions, where amphiphilic ANSG molecule effectively undergo template-induced supramolecular polymerization in the presence of both chiral ATP and achiral PPi templates. Chiral seed comprising [ANSG-ATP] effectively amplifies the overall supramolecular asymmetry when exposed to a mixture of achiral templates (PPi) and monomers (ANSG). This work further includes controlled non-covalent synthesis of 2D heterostructures like bottle brush and gradient heterostructures.
1B) Toward Programmable Supramolecular Topologies through Surface-Catalyzed Growth Hierarchical Supramolecular Polymerization:
Synthetic self-assembling systems often exhibit hierarchical morphologies under microscopic observation. However, most of these hierarchical structures arise in an uncontrolled manner. Due to post-synthetic agglomeration of polymer fibers, such hierarchical polymers tend to be highly polydisperse and structurally irregular. Much like biological protein assemblies formed under kinetic control, this area requires a bottom-up synthetic strategy that enables controlled hierarchical supramolecular polymerization by regulating the process from the nucleation stage rather than relying on post-polymerization events. This is where the importance of surface nucleation becomes evident. Here in our group we have employed chirality mismatch and bio-inspired inhibition strategies that drives supramolecular polymerization for Hierarchical structures.
1C) Crowding Effect in Supramolecular Polymerisation:
Macromolecular crowding is an inherent feature of cellular and synthetic environments that can strongly influence supramolecular polymerisation. By reducing the available free volume, crowding agents can increase the effective local concentration of assembling monomers, alter their diffusion, and modulate the thermodynamics and kinetics of nucleation and growth while taking advantage of the proximity effect between the monomers. These effects can further promote supramolecular polymerisation by favouring intermolecular association and stabilising assembled states. Understanding how macromolecular crowding regulates nucleation, elongation, and structural organisation provides our group with important insight for controlling supramolecular polymerisation.
