We performed systematic dewetting experiments on isotactic poly(para-methylstyrene) (iPpMS) films to explore the temperature dependence of the viscoelastic behavior of these films. We quantified the amount of residual stresses σ res induced through film preparation by spin-coating. As anticipated, σ res was found to be independent of the temperature T dew at which dewetting was done. A particular focus was on the temperature dependence of the relaxation time τ of σ res , which was measured with the help of three independent dewetting parameters. Within error, all three values of τ were identical and followed an Arrhenius behavior yielding an activation energy of 60 ± 10 kJ/mol. The initial dewetting velocity, being proportional to the ratio of surface tension of iPpMS and the corresponding viscosity, increased significantly with T dew . Assuming a linear stress−strain response, we deduced that the elastic deformation responsible for the maximum height of the dewetting rim increased with temperature, although σ res did not vary with temperature. Correspondingly, the shear modulus of iPpMS films was found to decrease monotonically with increasing temperature. Using a Maxwell-type model, the corresponding viscosity of the film showed the expected decrease with increasing temperature. Our experiments suggest that preparationinduced residual stresses affect material properties such as elastic modulus or viscosity of iPpMS as a function of temperature.

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When sound propagates in a porous medium, it is attenuated via several energy loss mechanisms which are switched on or o as the excitation frequency varies. The classical way of measuring acoustic energy loss in porous materials uses the Kundt impedance tube. However, due to its short length, measurements are made in the steady state harmonic regimes. Its lower cuto frequency is often limited to a few hundreds of Hertz.Two long acoustic waveguides were assembled from water pipes and mounted to create test-rigs for the low-frequency acoustic characterization of monolayer and stratied airsaturated poroelastic materials. The rst waveguide was straight and had a length of 120 m, while the second was coiled to gain space and was 135 m long. The long waveguides appeal to very low frequency measurements using impulsive acoustic waves (with rich spectral content) because the incident waves can be separated in time from echoes o the extremities of the guides. The transmission coecient of porous materials recovered using the two waveguides compared well with those from the transfer matrix method (TMM) used here in combination with Biot's 1962 theory to describe propagation in porous dissipative media. This wave-material interaction model permitted the recovery of the properties of poroelastic materials from transmitted acoustic waves propagating in air. The parameters involved are the Young's moduli, Poisson ratio and microstructural properties such as tortuosity and permeability. Being able to descend to lower frequencies guarantees the correct verication of the magnitude of the measured transmission coecient which approaches unity towards the static frequency. The coiled and straight 1 waveguides were found to be equivalent and provided data down to frequencies of the order of ≈ 12 Hz.