Metal Ion Responsive Functional Polymers With Different Backbone Structures PDF Download

Incorporating dynamic interactions into polymer matrices has emerged as a powerful tool to engineer materials for advanced applications. Metal-ligand coordination as the dynamic component has been a popular choice due to the diversity and ease of tailoring the functional sites without altering the backbone chemistry. Extensive theoretical and experimental studies have been conducted to unveil the fundamental science and critical mechanisms for better material design. The sticky Rouse model has been developed to describe the linear viscoelasticity of associative polymers neglecting the chemistry and structural details of bonding sites. Most of the experimental research on polymers containing metal-ligand coordination has focused on synthesis methods or the optical and mechanical effects resulting from bonds breaking and reforming. A gap between the theoretical understanding and the experimental findings exists due to the challenge of decoupling the metal-ligand interactions from other factors governing the bulk polymer behavior. In addition, the dynamic surface properties and ionic conductivity performances arising from metal-ligand coordination are less studied. This dissertation contributes to the understanding of the structure-property relationships of metal-ligand coordinated polymers by bridging the molecular metal-ligand coordination details and the macroscopic behavior of the materials with carefully designed model systems. This dissertation starts with a combined experimental and theoretical approach to quantitatively establishing how the stability and structure of metal-ligand interaction acting as dynamic crosslinks determines the viscoelastic characteristics of a metallopolymer. A model system which is free from solvent molecules, chain entanglement and phase-separation was designed to decouple the metal-ligand interactions from other factors governing the polymer behavior. By analyzing the key parameters extracted from the experimental results, the enhanced sticky Rouse model was proposed. This assists subsequent rational design of metal-ligand coordinated polymers with an easily accessible and implementable quantitative model. We then moved on to demonstrate that introducing metal-ligand coordination not only enables the dynamic characteristics of the polymer, but also raises other fascinating properties. This idea was elaborated in the following two works. First, we proposed a surface design approach to enable a reversible transition between hydrophobicity and hydrophilicity on the polymer surface in response to changing the environment polarity via "hiding" polar metal-ligand coordination sites under non-polar PDMS backbone. The dynamic characteristics of the bulk polymer is governed by network architecture and coordination strength, and is directly correlated to the speed and extent of the surface evolution. Second, we investigated the ionic conductivity of metal-ligand coordinated PDMS. The interaction between the ligands on a polymer chain and the metal cations from the salt added facilities the ion dissociation within the PDMS, and turns the non-conductive PDMS into an ionic conductive PDMS. The ionic transport mechanism was discussed in the context of the density and strength of metal-ligand coordination. Synergistic effects were observed and discussed for mixed lithium (Li) and copper (Cu) coordination, which shows the improved mechanical strength as well as ionic conductivity compared to the Li-coordinated PDMS. The systematic study on the structure-property relationships of polymers containing metal-ligand coordination in this dissertation provides insights to assist the design of advanced materials.