Porous elastomeric polymers have been used in a wide range of applications due to 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 materials properties were limited due to a lack of control over the chemistry used to prepare the crosslinked PDMS elastomer. Here, the synthesis of PDMS-based polymerized medium internal phase emulsions (polyMIPEs) with tunable storage shear moduli (G') have been prepared using macromolecular thiol-ene reactions. Storage shear moduli values from ~38 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 aqueous phase used in the emulsion formulation. Very low sound velocities (~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.

Wavelength-dependent light-responsive seleno-sulfide dynamic covalent bonds were used to prepare organogels with reversible changes in stiffness. The disulfide cross-link organogels prepared from norbornene-terminated poly­(ethylene glycol) (PEG-diNB) and poly­(2-hydroxypropyl methacrylate-stat-mercaptoethyl acrylate) (PEG-diNB-poly­(HPMA-stat-MEMA)) polymers underwent exchange reactions with 5,5′-diselenide-bis­(2-aminobenzoic acid) upon irradiation with UV light. Following irradiation with visible light, the seleno-sulfide bonds were cleaved, reforming disulfide cross-links and the 5,5′-diselenide-bis­(2-aminobenzoic acid). Reduction in G′ with disulfide–diselenide exchange was consistent with that observed following a thiol–disulfide exchange reaction. Recovery of G′ upon disulfide bond formation was 85–95% of the initial value in the as-prepared gel over five cycles of bond cleaving and reformation. This initial study shows the potential of the wavelength-controlled disulfide–diselenide chemistry to develop light-responsive reversible organogels. These organogels have the potential to be used in functional materials such as polymeric actuators or biomimetic soft robotics.