Mechanical properties of amorphous PEI, PES, and PVC up to 11 GPa studied by Brillouin light scattering

Abstract

We applied high-pressure Brillouin light spectroscopy to study the mechanical properties of representative amorphous polymers: polyetherimide (PEI), polyethersulfone (PES), and unplasticized polyvinylchloride (PVC). The pressure dependence of optical and elastic properties such as refractive indices and acoustic phonon velocities was obtained by employing both a forward, symmetric scattering and a backscattering geometry up to ~11 GPa. While PEI and PES showed longitudinal and transverse acoustic phonon modes simultaneously at above a certain pressure, PVC showed only one longitudinal acoustic phonon mode, which limited the access to further information. For PEI, PES, and PVC films, we successfully calculated pressure-dependent Poisson's ratios, bulk moduli, shear moduli, Young's moduli, and density-pressure isotherms. Furthermore, by using the Lorentz-Lorenz equation, we corroborated the conventional assumption that the mean polarizability of polymeric materials is nearly constant even when pressure is applied.