Aromatic polyamides with tunable secondary structures and enantioseparation properties Subhendu Samanta and Raj Kumar Roy* Department of Chemical Science, IISER Mohali, India Abstract Over the past two decades, researchers have been focusing on developing folding scaffolds with tunable conformations reminiscent of biomolecules. 1 Apart from their folded structures, those foldamers often contain well-defined pockets that can selectively encapsulate guest molecules. 2 Such host-guest interactions may also alter the conformation of the initial folded structure resulting in a tunable secondary structure. 3 This presentation emphasizes altering the aromatic polyamides’ conformation through strategic side-chain modifications and showcasing versatile applications. Our previous work demonstrated the synthesis and characterization of polyethylene glycol (PEG) functionalized aromatic polyamides, exhibiting an intrachain β-sheet-like conformation (in solution) via the cooperative effect of H-bonding and π-stacking. 4 In this present work, our objective was to tune the secondary structure of the aromatic polyamides from β-sheet to helix through side-chain modifications. Thus, replacing achiral PEG side chains with chiral azido acids causes chirality transfer from pendant side chains to polyamide backbone resulting in a helical structure and was characterized experimentally. Chiral pendant groups can excellently manipulate the handedness of induced chirality in the aromatic backbone. However, suitable external guest molecules can restore the aromatic π-stacking dominated achiral sheet-like structure through host-guest complexations. Interestingly, inviting guests with amine-functionalized aromatic π-surfaces excellently imparts chirality to the backbone. Finally, I will also demonstrate the possibility of enantio-separations using chiral polyamides and their helical structure.
References 1. Saraogi and A. D. Hamilton, Chem. Soc. Rev. , 2009, 38 , 1726 2. A. Sobiech, Y. Zhong and B. Gong, Org. Biomol. Chem. , 2022, 20 , 6962. 3. D.-W. Zhang, X. Zhao and Z.-T. Li, Acc. Chem. Res. , 2014, 47 , 1961. 4. S. Samanta, D. Mallick and R. K. Roy, Polym. Chem. , 2022, 13 , 3284.
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