Dynamics of supramolecular entangled polymeric assemblies based on linear telechelic chains and metal-ligand interactions

Details

Supervisors

Van Ruymbeke, Evelyne

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil en chimie et science des matériaux

Abstract

Supramolecular polymers are a class of material that is attracting a great deal of attention in the field of material science, thanks notably to their dynamic properties and high versatility. However, due to their reversibility, their properties are usually much more complex than those of standard polymers. The aim of this master's thesis is thus to investigate the dynamics of entangled supramolecular assemblies based on linear telechelic chains from a rheological point of view. All the samples investigated are based on the same entangled poly(n-butyl acrylate) precursor functionalised at both ends by a terpyridine ligand. The supramolecular interactions are based on the complexation of these terpyridine ligands with two different transition metal ions, Zn(II) and Cu(II), added in different amounts to the sample. When complexes are formed between ligands and ions, the building blocks become associated, creating long linear assemblies. The data obtained from Dynamic Frequency Sweep measurements are analysed, and the first observations resulting from the examination of the curves are then verified by means of a numerical simulation based on a tube-based model, which describes the chains at the mesoscopic length scale. In order to account for the supramolecular nature of our samples, two versions are developed, each one relying on different assumptions, in order to better capture the complexity of the behaviour of these polymers. Good agreement between the theoretical and experimental data is found by combining this tube model with the Cate’s theory. By looking at the dependence of the modelling parameters in function of the polymer characteristics and temperature, we extract important information on the sample dynamics. In particular, the presence of aggregates is detected and quantified. We then show that the lifetime of the complexes follows, in general, an Arrhenius dependence as a function of temperature. The fact that more complexes are created upon an increase of the ion density is also discussed. It is finally observed that the nature of the ions has a large influence on the polymer properties, which is attributed to their different lability as well as their different tendency to form aggregates. In conclusion, this work allows us to better understand the influence of temperature, ion density, and ion nature on the dynamics of entangled telechelic linear polymers.