Characterization of polydisperse samples: from their rheology to their composition

Details

Supervisors

Van Ruymbeke, Evelyne

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil en chimie et science des matériaux, à finalité spécialisée

Abstract

enThis Master’s thesis investigates the characterization of polydisperse polystyrene systems by combining linear rheological measurements with an inverse modelling approach. The objective is to extract molecular weight distributions from experimental viscoelastic data and to assess the reliability and limitations of rheology-based inverse methods. An extensive literature review is first conducted to establish the theoretical background of inverse rheological modelling. Well-defined polystyrene samples and blends containing a polydisperse component are then prepared and characterized using rheology and gel permeation chromatography. An inverse algorithm based on tube models and the Time-Marching Algorithm is implemented and applied to both literature data and experimental blends. The results show that while very good fits of rheological data can often be obtained, the inverse problem is intrinsically ill-posed, leading to non-unique solutions that strongly depend on initial conditions. This work highlights both the potential and the limitations of inverse rheological modelling for molecular characterization, with perspectives toward complex and recycled polymer systems.