Intrinsically Dynamic Covalent Polymers

Project Information

IDCP

Grant agreement ID: 101025041

DOI

10.3030/101025041

Project closed

EC signature date 10 March 2021

Start date 1 April 2021

End date 31 March 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 187 572,48

EU contribution

€ 187 572,48

Coordinated by

RIJKSUNIVERSITEIT GRONINGEN
Netherlands

Periodic Reporting for period 1 - IDCP (Intrinsically Dynamic Covalent Polymers)

Reporting period: 2021-04-01 to 2023-03-31

Summary of the context and overall objectives of the project

The future materials for our sustainable society and industry requires the design of synthetic materials that combine robustness, greenness, and low-environmental impact with sustainability, dynamic functions, and recyclability. One of the green chemistry principles for future functional materials is to use reversible noncovalent bonds to replace stable covalent bonds. However, it usually results in a significant loss in materials’ mechanical strength, as well as the inevitable use of solvents to support the noncovalent interactions in most cases. Therefore, it is a major challenge how to exploit synthetic polymers that simultaneously exhibit the robustness of covalent polymers, show the intrinsic reversibility of supramolecular noncovalent polymers and ultimately allow adaptive/responsive behaviors.

The overall objective of this project is to construct a family of intrinsically dynamic covalent polymers based on 1,2-dithiolanes. The inherent dynamic nature of disulfide bonds, the bonds crosslinking peptides, provides many opportunities to design materials with fascinating dynamic functions, such as self-healing ability, stimuli-responsive properties and recyclability. This project focused on 1,2-dithiolanes, a family of cyclic disulfides, to explore the dynamic chemistry of disulfides and their polymers. The main body of the researches supported by this project covers several sections, including i) expanding the molecular structures of monomers to enhance the material properties of poly(disulfide)s, ii) the dynamic chirality of disulfide bonds and their adaptive properties in noncovalent environments; iii) the de novo design of symmetric 1,2-dithiolanes to generate biomimetic helical polymers that behave like proteins. Section (I) achieved a series of advanced functional materials based on the synergy of disulfide bonds with other dynamic chemical bonds (e.g. reticular hydrogen bonds of acylhydrazines, orthogonal dynamic covalent bonds of acylhydrazones, etc.), which overcome the difficulties between material robustness and dynamic functions. A few material performances, such as Young’s moduli and self-healing properties, have been achieved at a level of the state of the art. The disclosed underlying mechanisms are significant for designing such dynamic materials in the future. Section (II) focused on a series of 1,2-dithiolanes modified with chiral amino acids, revealing the important chirality transfer mechanism from the fixed chirality of amino acids to the dynamic chirality of disulfide bonds.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

1. Acylhydrazine-based reticular hydrogen bonds enable robust, tough and dynamic supramolecular materials
Supramolecular materials are widely recognized among the most promising candidates for future generations of sustainable plastics because of their dynamic functions. However, the weak noncovalent crosslinks that endow dynamic properties usually trade off materials’ mechanical robustness. This result presents the discovery of a simple and robust supramolecular crosslinking strategy based on acylhydrazine units, which can hierarchically crosslink the solvent-free network of poly(disulfides) by forming unique reticular hydrogen bonds, enabling the conversion of soft into stiff dynamic material. The resulting supramolecular materials exhibit increase in stiffness exceeding two to three orders of magnitude compared to those based on the hydrogen-bonding network of analogous carboxylic acids, simultaneously preserving the repairability, malleability, and recyclability of the materials. The materials also show high adhesion strength on various surfaces while allowing multiple surface attachment cycles without fatigue, illustrating a viable approach how robustness and dynamics can be merged in future material design.

2. Stereodivergent chirality transfer by noncovalent control of disulfide bonds
Controlling dynamic stereochemistry is an important challenge as it is not only inherent to protein structure and function but often governs supramolecular systems and self-assembly. Typically disulfide bonds exhibit stereodivergent behavior in proteins, however, how chiral information is transmitted to disulfide bonds remains unclear. This result reports that hydrogen bonds are essential in the control of disulfide chirality and enable stereodivergent chirality transfer. The formation of S-S···H-N hydrogen bonds in solution can drive conformational adaption to allow intramolecular chirality transfer, while the formation of C=O···H-N hydrogen bonds results in supramolecular chirality transfer to form antiparallel helically self-assembled solid-state architectures. The dependence on the structural information encoded in the homochiral amino acid building blocks, reveals the remarkable dynamic stereochemical space accessible through non-covalent chirality transmission.

The exploitation and dissemination of the results supported by this project has been pushed by i) publishing in high-level scientific journals including Science Advances, JACS, and Angew. Chem. with more than 10,000 times of read online. The researcher has presented the researches in several international conferences including IUPAC Green Chemistry Conference, EuChemS Congress, and American Chemical Society. A cover art has been published in JACS to disseminate the results.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Substantial progress have been made by this project in developing the dynamic polymerization and chirality of cyclic disulfides. The material properties of self-healable poly(disulfide)s have been promoted by the result of this project towards the GPa level of Young’s modulus, achieving the combination of mechanical robustness and self-healing ability in a single material. Meanwhile, the orthogonal dynamic covalent chemistry also allowed GPa-level dynamic materials capable of recycling back to the original monomers. This project has pioneered the discovery of S-S-mediated hydrogen bond and disclosed its important role in delivering the chirality from amino acids to disulfide bonds, supporting a conceptually new principle in terms of disulfide stereochemistry under noncovalent control.
Several researches are expected to be submitted or to be published in high-level journals until the end of this project. One is the discovery of 20 X-ray single crystal structures of chiral 1,2-dithiolanes that self-assemble into very unusual helical supramolecular structures in solid states. The other is the first synthesis of a dynamic covalent helical poly(disulfide) polymer that performs biomimetic folding and recycling function in a single molecular system. The impact of the results is going to unveil the fundamental aspects of dynamic chirality of disulfide bonds under noncovalent control, which is vital for many scientific topics such as the origin of chirality in life, the inner principles of protein folding and recycling, etc. Several scientific communities will be interested and involved such as material science, physical organic chemistry and structural biology.

Overview of the project IDCP