Fabrication and Characterization of Porous Poly(dimethylsiloxane) (PDMS) Adhesives

In this study, we propose a simple low-cost emulsion-based method to fabricate porous poly(dimethylsiloxane) (PDMS) adhesive films, with a focus on their possible application as wound dressings. In this method, water is added to PDMS to form an emulsion. On film-casting the emulsion and curing it at 120 degrees C, evaporation of water droplets and PDMS cross-linking result in randomly distributed pores/voids in the bulk of the PDMS film. A huge advantage of the proposed method over conventional approaches is its simplicity owing to the use of water as a porogen. Two variants of the fabrication approach were considered: direct film-casting of emulsion and film-casting of the solvent-mediated emulsion with additional degassing. Films prepared using the first approach demonstrated that the bulk porosity induces significant roughness at their surface. Such films do not make good contact with the substrate, resulting in poor adhesion. Coating the films with a thin viscoelastic layer of PDMS, while retaining the bulk structure, improves the contact of the film with the substrate. These bi-layer films demonstrated remarkable enhancement in adhesion. The second approach involves adding ethyl acetate as a solvent and degassing the emulsion before film-casting, which results in a more controlled porosity and lower roughness at the surface. Compared to the porous films synthesized using the former protocol, these films have a relatively improved contact with the cover plate, resulting in enhanced adhesion. Lastly, through falling weight impact measurements, it was shown that the porous films, in comparison to their nonporous counterpart, were more effective in absorbing the accidental impact shock, which makes them potentially useful in healthcare applications.