Controlling the viscoelastic properties of supramolecular networks based on topological or metallo-supramolecular associations
(2021)
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- Abstract
- Polymer gels and networks, which are formed by “strands”-connected together via covalent or supramolecular “junctions”, are the most versatile, widely studied and broadly used materials. There are several types of polymeric networks. One of them is the supramolecular polymer networks, which are three-dimensional structures of cross-linked macromolecules connected by transient, supramolecular bonds such as hydrogen bonding, transition metal complexation, π–π stacking and interlocked interactions. They are soft materials, with huge potential for exhibiting properties such as self-healing, and shape-memory. A very peculiar, kind of network has recently emerged, called “slide-ring gels”. Their main cross-linking process is due to topological bonds made of two macrocycles linked together in a figure-of-eight shape, each with a polymer chain threaded into its cavity. These cross-links are not fixed and can slide along the polymer chains of the network, the complete unthreading of the chain being prevented by bulky groups attached to its extremities. As another kind of modulable polymer network, metal−ligand (ML) coordination complexes and the corresponding metallo-supramolecular polymers (MSPs) are particularly interesting, since the binding characteristics and materials properties can be tailored through the choice of the multiligand monomer as well as the nature of the metal ion and counterion from which these materials are assembled. The well-defined reversible junctions of the supramolecular polymers can be also phase-separated into aggregates and form clusters due to the difference in polarity between the supramolecular junctions and the polymer backbone. The objective of this research work is to study the dynamics of two different well-defined supramolecular networks and to understand their unique viscoelastic behavior. This requires determining the relationship between the composition and the viscoelastic properties of these materials, which could serve as a base to help to design a new class of smart material with extraordinary properties. In the first part of the thesis, we study the dynamics of the well-defined slide-ring gels. In order to understand the influence of each component present in the slide-ring gels, we first investigate the dynamics of the polymer chain used for building the gels, as well as the polyrotaxane samples, which contain several rings along the chain backbone. Then, these results are used to investigate the dynamics of the slide-ring gels, which are formed by cross-linking the rings of the polyrotaxanes. The controllable structure of these last ones allows us to understand the effect of structural parameters such as the influence of rings mobility, rings distance, or rings density on their dynamics. The second part is related to investigating and understanding the viscoelastic properties of the metallo-supramolecular phase separated networks and finding how the structure and thermomechanical properties of these supramolecular networks are influenced by temperature, by the nature of the metal ions and by the amount of metal ions added into the system. In particular, we try to understand the relationship between the different morphologies of the sample and its viscoelastic properties, both properties depending on its thermal equilibration.
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Ghiassinejad, S. (2021). Controlling the viscoelastic properties of supramolecular networks based on topological or metallo-supramolecular associations. https://hdl.handle.net/2078.5/114514