Development of a nanorheometer to study rheological behaviour of confined polymers
Résumé
The characterisation of rheometrics properties at nanometric scale has a great interest in the comprehension of phenomena producted by polymer adsorbed or grafted on a surface. The aim of that study is to describe the development of a dynamic nanorheometer to show the influence of the confinement of grafted polybutylacrylate, which is a viscoelastic liquid at room temperature. The first part shows how, on the base of a commercial nanoindenter, we have developed a surface force apparatus with a sphere/plate geometry. The interest is to measure the shear modulus G* in a large pulsation range at different thicknesses (and 0 with a drainage force measurement). The calibration determines the limits of the apparatus: thicknesses from 10 nm to 10 µm, temperature from 5 to 35°C with 0,01°C precision, pulsations from 0,01 to 1000 rad/s and viscosity in a large range. This study has been done with several polymer, in particular adsorbed PDMS with viscosity from 60 to 1000 Pa.s, and has shown that we can use this apparatus to characterise macroscopic rheometrics properties of polymer with only one drop. Then, we will show the influence of the confinement on the variation of G*, particularly the apparition of a plateau at low frequencies for G’. At present time, we have studied grafted polymer with molecular weight more important than the bulk’s one and with density of about 0,5 molecule.nm-2 (stretched brush). A three layers model has been developed to analyse the results.
Origine : Fichiers produits par l'(les) auteur(s)