Key Takeaways & Executive Findings
- •• • The helical poly(disulfide) system achieves complete chemical recyclability to monomers, with depolymerization monitored in real-time at 363 K in C2H2Cl4, demonstrating closed-loop recycling under mild thermal conditions. • • Incorporation of the dipeptide motif AA-L-Ala-L-Ala establishes stable β-sheet-like hydrogen bonds, increasing helical content and stability, as evidenced by temperature-varied CD and UV-vis spectra at 3 g L−1 in C2H2Cl4. • • Thermal treatment reorganizes nanocrystalline polymers into semicrystalline rod-like flexible cylinders with diameter ~2.1 nm and length ~25 nm, enabling hierarchical assembly into columnar liquid crystal phases. • • The dual dynamic system (dynamic disulfide bonds and hydrogen bonds) provides conformational resilience up to high temperatures, maintaining rod-like shape and helical conformation, which is critical for applications requiring thermal stability and recyclability.
Abstract
Biopolymers such as proteins exhibit both stability and dynamic properties, reflected in precise conformational adaptability and reversibility within cells. Simulating this dual dynamic nature in fully synthetic covalent polymers has been a major challenge, aiming to enable a single material to reversibly transform between defined helical conformations and random coils, and to be fully recycled back to original building units. Recently, Zhang, Qu, Feringa and co-workers reported a groundbreaking advance in Nature Chemistry, achieving a helical covalent polymer with reversible conformational switching between ordered and disordered states while maintaining complete chemical recyclability to its monomers. This system is built on poly(disulfide)s, utilizing biologically relevant building blocks (1,2-dithiolane asparagusic acid, AA) and amino acid derivatives. Monomers undergo reactive ring-opening polymerization (ROP) initiated by sodium bisulfate under mild conditions, forming polymers that exhibit reversible conformational interconversion between disordered coils and helical structures. Incorporation of a dipeptide motif (AA-L-Ala-L-Ala) establishes stable extended β-sheet-like hydrogen bonds, improving helical stability. Following polymerization, nanocrystalline polymers can be reorganized into semicrystalline structures upon thermal treatment, yielding rod-like flexible cylinders approximately 2.1 nm in diameter and 25 nm in length. Structural analyses reveal hierarchical organization, including β-sheet-stabilized rod-like flexible cylinders and columnar liquid crystal assemblies, imparting remarkable thermal stability and conformational resilience. The dual energy landscapes govern monomer-polymer equilibrium and conformation-dependent closed-loop recycling, enabling intrinsic reconfigurability among small-molecule monomers, random coils, and helical poly(disulfide)s, triggered by temperature.
1. Introduction
Conventional synthetic polymers lack the dual dynamic nature of biopolymers, which combine conformational adaptability with reversible recyclability. Existing approaches to mimic protein-like behavior often rely on non-covalent interactions alone, yielding materials that are either too fragile or non-recyclable. The challenge is to design a covalent polymer that can switch between ordered helical and disordered random coil states while being fully depolymerizable to its monomers under mild conditions.
This highlight addresses that bottleneck by presenting a poly(disulfide) system that integrates dynamic covalent disulfide bonds with hydrogen-bond-directed folding. The synergy enables reversible conformational switching and complete chemical recyclability, overcoming the limitations of previous systems that lacked well-defined secondary structures or recyclability. The use of biologically derived building blocks and mild polymerization conditions further enhances its practical relevance.
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Ming Kang, Jiong Zhou (2026). Synergy of Dynamic Covalent Bonds and Hydrogen Bonds Enables Dual Dynamic Recyclable Helical Polymers. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4042-6
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Frequently Asked Questions
What is the mechanism behind the reversible conformational switching between helical and random coil states?
The switching is driven by the interplay between intramolecular hydrogen bonds (from the dipeptide motif) and dynamic disulfide bond exchange. Temperature changes alter the balance, allowing the polymer to transition between ordered helical and disordered coil conformations, as confirmed by temperature-varied CD and UV-vis spectroscopy.
How is complete chemical recyclability achieved, and what are the conditions for depolymerization?
Depolymerization is triggered by temperature, with real-time UV-vis monitoring at 363 K in C2H2Cl4 showing the breakdown of the polymer back to its monomers. The closed-loop recycling is governed by the dual energy landscapes, enabling recovery of original building units without degradation.
What is the thermal stability limit of the helical conformation?
The helical conformation and rod-like shape are maintained even at high temperatures, as indicated by the thermal stability imparted by the supramolecular architecture. Specific temperature thresholds are not provided in the text, but the system shows resilience under conditions that would typically disrupt secondary structures.
What are the dimensions and structural features of the resulting assemblies?
After thermal treatment, the polymers form rod-like flexible cylinders with a diameter of approximately 2.1 nm and a length of around 25 nm. These cylinders organize into columnar liquid crystal assemblies, stabilized by β-sheet-like hydrogen bonds.
What is the significance of using biologically relevant building blocks like asparagusic acid?
Using 1,2-dithiolane asparagusic acid (AA) and amino acid derivatives provides a sustainable and biocompatible basis for the polymer. It also facilitates the formation of hydrogen bonds and disulfide bonds, which are essential for the dual dynamic behavior, and aligns with green chemistry principles.
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