As the size of microelectronic devices reaches the micro-scale, the processing speed of these devices depends on the integration of low-k materials. The introduction of nanopores into these materials significantly reduces the dielectric constant, but also jeopardizes the mechanical integrity of the material. Furthermore, processes during fabrication such as chemical-mechanical planarization (CMP) subject the material to aqueous solutions, which may have deleterious effects on the mechanical properties of the dielectric material. The low-k material of interest is nanoporous methylsilsesquioxane (MSSQ), which has a dielectric constant of k~2.0. The rate of diffusion of these solutions into thin-film structures containing MSSQ was investigated. In addition, the effect of CMP chemistry on the subcritical crack growth was explored. This information was used to predict the lifetime of a device in the presence of CMP solutions.