Liquid absorption-induced photoelasticity of polydimethylsiloxane

In the paper, we present the results of the investigation of optical birefringence induced in spatially confined PDMS samples immersed in isopropanol and acetone. The PDMS samples are gradually deformed as they swell due to absorbing the liquid and become optically birefringent due to subsequent deformation. We investigate their birefringence in the spectral range from 400 nm to 700 nm using a plane polariscope by monitoring the change of the spectral distribution of the light passing through the PDMS samples in time. The observation time is in the order of days. The time dependences of the normalized light intensity are used to determine the time evolution of the birefringence dispersion. We propose a function Δ n ( t ) expressing the time dependence of PDMS birefringence induced due to its interaction with the used liquids. The function's behavior agrees very well with the time dependence of the birefringence dispersion obtained from the measured light intensity. The obtained match between calculated and measured time dependences of the normalized light intensities also manifests the appropriateness of the proposed Δ n ( t ) function.