Storage Moduli and Porosity of Soft PDMS PolyMIPEs Can Be Controlled Independently Using Thiol-Ene Click Chemistry

Porous elastomeric polymers have been used in a wide range of applications because of their unique characteristics such as biocompatibility, gas permeability, thermal stability, and hydrophobic and dielectric properties. Poly(dimethyl siloxane) (PDMS), a commercially available elastomer, has also been shown to exhibit specific acoustic properties. However, the material properties were limited because of a lack of control over the chemistry used to prepare the cross-linked PDMS elastomer. Here, the synthesis of PDMS-based polymerized medium internal-phase emulsions (polyMIPEs) with tunable storage shear moduli (G') has been performed using macromolecular thiol-ene reactions. Storage shear modulus values from similar to 38 to similar to 330 kPa were achieved by changing the stoichiometric ratio of the thiol-to-ene-functionalized PDMS, whereas the porosity of the polyMIPEs was controlled by the volume of the aqueous phase used in the emulsion formulation. Very low sound velocities (similar to 40 m/s) through the porous materials were recorded using acoustic characterization. Therefore, this work provides an example of the synthesis of soft polyMIPEs with possible applications as acoustic materials.