Li, Yanzhao
[UCL]
Metallosupramolecular polymers (MSPs) exhibit a very complex and interesting rate- and time-dependent mechanical behavior, which strongly depends on the dynamics of metal ligand coordination. The strength and dissociation rate of the metal ligand bonds can be tuned to a great extent by regulating the physico-chemical parameters allowing to create materials with tunable viscoelastic properties. Under specific conditions, the metal ligand complexes in the melt state could further aggregate into clusters providing a route to control the material morphology and to improve their mechanical properties. In addition, the assembly and rheological behavior of MSPs has a large dependence on the building blocks architecture and the presence of entanglements. In particular, the latter can interact with the dynamics of the metal ligand bonds/clusters. Furthermore, a new strategy that combines two supramolecular interactions within the same material has emerged recently to obtain material with a double dynamics behavior. Therefore, this thesis aims to systematically understand how the structure and dynamics of single and double dynamics MSPs are influenced by the density of metal ligand bonds, the building blocks architecture, or the presence of clusters. We use entangled terpyridine end-capped telechelic linear and star poly(n-butyl acrylate) (PnBA) and two pairs of metal ions to form single or double dynamics MSPs. The structure and dynamics of the corresponding MSPs are investigated by several experimental techniques combined with theoretical models. The results show that the dynamics of resulting materials are governed by the interplay between disentanglement process and dissociation/re-association dynamics of metal ligand crosslinks/clusters, which strongly depends on the ion nature, ion content, ion pairs and temperature. In particular, the stress relaxation behavior of the double dynamics materials is found to be either between the ones of the two single dynamic materials, or slower than those of single dynamic materials. On the other hand, we investigate the rheological properties of photo-crosslinked polymer networks to understand how the photo-crosslinking kinetics is influenced by the physical state and the molecular weight of the precursors. We found that a higher crosslinking density is obtained for lower molecular weight precursor photo-crosslinked in the molten state. Based on a systematic study of different systems, this work presents different possibilities for the controlled design of materials with desirable properties.


Bibliographic reference |
Li, Yanzhao. Dynamics of metallosupramolecular polymers and networks. Prom. : Van Ruymbeke, Evelyne |
Permanent URL |
http://hdl.handle.net/2078.1/274389 |