Stage M1/M2 in polymer physical-chemistry

from Feb/March to June/July 2023

Context. The Solvay group develops materials and products intended for specialty chemicals markets (e.g. detergents, cosmetics, aeronautics, automotive) among which polymers occupy an important place. The group works on the synthesis by radical polymerization of either hydrophobic or hydrophilic copolymers. The characterization of these copolymers is an essential step, to validate the synthesis and understand the relationship between the properties of the polymers and their chemical structure (e.g. heterogeneity of the distribution of chemical composition). GPEC (Gradient Polymer Elution Chromatography) is a liquid polymer chromatography technique that separates polymers according to their chemical composition. The interaction of the polymer chains with the stationary phase as well as the solubility of the polymer in the solvents are the key parameters that govern the elution in GPEC. An in-depth knowledge of the cross-interaction between the polymer, the stationary phase and the solvent would considerably reduce development times and increase efficiency of the technique.

Objective. Molecular dynamics simulation has been identified as a promising tool for optimizing the separation of polymers, through a collaboration between Dr. Fabrice Brunel (Lecturer at the CP2M laboratory) and the Solvay group. The umbrella sampling technique[1] allows the reconstruction of the interaction profiles between a polymer and a surface, which makes possible to better understand the enthalpic and entropic mechanisms involved during chromatographic separation.[2]

Method. The molecular dynamics simulations will be carried out using gromacs software. First, the simulations (all atoms- OPLS) of different polymers and copolymers in various solvents will be produced. The results of these simulations will be compared to their physico-chemical characterization: solubility assays and measurement of the radius of gyration by smallangle X-ray scattering. Then, the umbrella sampling simulations will be performed with the selected pair of solvents. The development of the surface force field will require particular attention. A coarse-grain model (Martin Force-Field)[3] of the system will be developed in order to reduce the calculation time while increasing the molar mass of the polymers. Finally, the results of the simulations will be applied and evaluated by GPEC experiments.

Location. CP2M laboratory (Catalysis, Polymerization Processes & Materials). CPE building, La Doua Villeurbanne.

Contact. Candidates with theoretical background in Physico-Chemistry or Physics, ideally with experience in simulation, are welcome to contact Fabrice Brunel (fabrice.brunel@univ-lyon1.fr).

[1] Lemkul et al. J. Phys. Chem. B 2010, 114, 4, p1652–1660

[2] Brunel et al. Macromol. Chem. Phys. 2019, 220, p1800496 ; Brunel et al. J. Phys. Chem. B, 2019, 123, 30, p6609-6617

[3] Souza et al. Nature Methods, 2021, vol. 18, p382-388