Liquid-Repellent Films Comprising Octamethylsilsesquioxane Selected Based on Three-Dimensional Solubility Parameters

On the basis of Hansen solubility parameters (HSP), we investigated octamethylsilsesquioxane (OMS), a siloxane compound with a cage-like structure and methyl side chains, as an omniphobic substance. The HSP of OMS were determined through dissolution tests to be similar to those of polytetrafluoroethylene (PTFE), leading to the prediction that films comprising OMS should possess liquid-repellency comparable to films comprising PTFE. Indeed, an electroless-plated Ni-P film composite with OMS particles (Ni-P/OMS film) exhibited liquid-repellency comparable to or higher than that of the Ni-P film composite with PTFE particles, except toward 1-bromonaphthalene, which has a low surface free energy. Moreover, the hydrophilic influence of the Ni-P matrix was eliminated by the use of polydimethylsiloxane (PDMS) as the matrix instead of Ni-P, resulting in enhanced liquid-repellency and water-sliding behavior of the solution-sprayed PDMS film composite with the OMS particles (PDMS/OMS film). These films comprising OMS particles are promising candidates for nonfluorinated liquid-repellent films.