Effect of the pore structure on the properties of nanoporous silsesquioxane thin film

Two classes of porous silsesquioxane (SSQ) based thin films with different porosities have been successfully prepared with functionalized cyclodextrin (CD) derivatives. The first class of the films contained only micropores (<2 nm) and the second one contains large embedded voids (>10 nm) interconnected through tiny micropores. Dependence of dielectric constant, mechanical properties and solvent diffusivity on porosity and pore structure is discussed. The dielectric constant of the films depend mainly on porosity regardless of the pore structure (size, distribution, and interconnection). The difference of pore structure of two porous film system does not significantly affect the mechanical property such as film’s modulus in this system. The thermal stress behavior of the films strongly correlated with the pore structure. The second class of the films has smaller value of single stress of the films. Diffusivity of organic solvents in the films containing micropores (<2 nm) monotonically increases with the film’s porosity. A clear transition of diffusion behavior in the second class of the porous films represents percolation threshold of the voids.