High-pressure elasticity of poly(methyl methacrylate) up to 31.5 GPa studied by Brillouin spectroscopy

Hydrostaticity of poly(methyl methacrylate) loaded in a diamond anvil cell for high-pressure study

“…The substantial increase in the Brillouin frequency shift of the LA mode of PMMA at low pressures below ~2 GPa is attributed to the reduction and complete collapse of free volume in PMMA [9]. This process is also accompanied by the rapid increase in the density at the early stage of compression [11]. Fig.…”

“…The LA mode frequency increases upon compression, which reflects the densification of PMMA. The refractive index also increases with increasing pressure [11]. If the pressure inside the DAC deviates from the condition of hydrostaticity significantly, the PMMA is compressed under anisotropic (uniaxial) pressure, and more than two elastic stiffness coefficients are necessary for describing the stress-strain relationship.…”

“…On the other hand, if polymeric materials are to be investigated, they may be put into the gasket hole without any pressure medium. This method has been used to measure the EOS of several polymeric materials up to a few tens of GPa [6][7][8][9][10][11][12], for example, ~85 GPa for the Kel F-800 copolymer by using Brillouin scattering spectroscopy [9]. However, a recent Brillouin scattering study on polycarbonate seems to indicate that the condition of hydrostatic pressure may be seriously broken for the polymer once it is included in the DAC without any pressure medium [13].…”

“…The EOS of polymers relates the density to the pressure. The EOS can be derived from the sound velocity, which can be calculated from the Brillouin frequency shift [6][7][8][9][10][11][12][13]. Since the Brillouin frequency shift is the only necessary information for the calculation of EOS, the same Brillouin shift under different M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 4 experimental conditions guarantees the same EOS of the materials loaded in DAC.…”