Bioinspired dual self-folding of single polymer chains via reversible hydrogen bonding

Abstract

With the long term aim of preparing synthetic macromolecules that mimic the folding actions of natural biomacromolecules, a single synthetic polymer chain containing two distinct and orthogonal hydrogen bonding recognition motifs has been synthesized using an atom transfer radical polymerization (ATRP) and orthogonal ligation strategy. The hydrogen bonding recognition units, based on both three-point thymine (Thy)–diaminopyridine (DAP) and six-point cyanuric acid (CA)–Hamilton wedge (HW) interactions, induced—at low concentrations—a single chain self-folding process. The self-assembly process was monitored—initially between small molecule models—by proton nuclear magnetic resonance (1H NMR) spectroscopy, revealing full orthogonality of the two recognition pairs, HW–CA and Thy–DAP. Dynamic as well as static light scattering (DLS and SLS) analyses of the macromolecular self-assembly systems provide unambiguous evidence for the hydrogen-bonding interactions between both the Thy–DAP and CA–HW units leading to well-defined dual point single chain self-folding, indicating that more complex single chain self-assemblies based on synthetic polymers should be able to mimic—on a simplified level—the folding actions of natural biomacromolecules. The reversibility of the self-folding action depends on temperature as confirmed via1H-NMR spectroscopy in [D2]tetrachloroethane.