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.
