Redox-Mediated, Transient Supramolecular Charge-Transfer Gel and Ink.

Unprecedented spatiotemporal control exhibited by natural systems has aroused interest in the construction of its synthetic mimics. Cytoskeleton proteins utilize fuel-driven dissipative self-assembly to temporally regulate cell shape and motility. Until now, synthetic efforts have majorly contributed to fundamental strategies; however, temporally programmed functions are rarely explored. Herein, we work toward alleviating this scenario by using a charge-transfer (CT) based supramolecular polymer that undergoes structural changes under the effect of a redox fuel. The structural changes in supramolecular assembly amplify into observable macroscopic and material property changes. As a result, we achieve transient chemochromism,  a self-erasing ink and self-regenerating hydrogel, whose temporal profile can be regulated by varying the concentrations of the chemical cues (fuel and enzyme). The redox-mediated transient functions in the CT based supramolecular polymer pave way to create next-generation active, adaptive, and autonomous smart materials.

Transient dormant monomer states for supramolecular polymers with low dispersity.

Temporally controlled cooperative and living supramolecular polymerization by the buffered release of monomers has been recently introduced as an important concept towards obtaining monodisperse and multicomponent self-assembled materials. In synthetic, dynamic supramolecular polymers, this requires efficient design strategies for the dormant, inactive states of the monomers to kinetically retard the otherwise spontaneous nucleation process. However, a generalized design principle for the dormant monomer states to expand the scope of precision supramolecular polymers has not been established yet, due to the enormous differences in the mechanism, energetic parameters of self-assembly and monomer exchange dynamics of the diverse class of supramolecular polymers. Here we report the concept of transient dormant states of monomers generated by redox reactions as a predictive general design to achieve monodisperse supramolecular polymers of electronically active, chromophoric or donor-acceptor, monomers. The concept has been demonstrated with charge-transfer supramolecular polymers with an alternating donor-acceptor sequence.

Temporal switching of an amphiphilic self-assembly by a chemical fuel-driven conformational response.

The spatial and temporal control of self-assemblies is the latest scientific hurdle in supramolecular chemistry which is inspired by the functioning of biological systems fueled by chemical signals. In this study, we work towards alleviating this scenario by employing a unique amphiphilic foldamer that operates under the effect of a chemical fuel. The conformational changes in the foldamer amplify into observable morphological changes in its amphiphilic assembly that are controlled by external molecular cues (fuel). We take advantage of this redox responsive foldamer to affect its conformation in a temporal manner by an enzymatic pathway. The temporal characteristics of the transient conformation/assembly can be modulated by varying the concentrations of the fuel and enzyme. We believe that such a design strategy can have positive consequences in designing molecular and supramolecular systems for future active, adaptive and autonomous materials.

Mixed donor-acceptor charge-transfer stacks formed via hierarchical self-assembly of a non-covalent amphiphilic foldamer.

A non-covalent, amphiphilic foldamer design leads to an efficient charge-transfer complex between dipyrene (donor) and naphthalene diimide (acceptor) derivatives, which further self-assembles into one-dimensional nanofibers with an alternate (mixed) donor-acceptor arrangement.