Porous methylsilsesquioxane (MSQ, CH3SiO1.5) films were created by making polymer blends with trimethoxysilyl norbornene (TMSNB) and triethoxysilyl norbornene (TESNB), where the polymer served as a sacrificial place-holder. Upon exposure to elevated temperatures, the polymers decomposed within the MSQ matrix to form nanosize voids in the films. Different pore microstructures were observed by transmission electron microscopy and atomic force microscopy, depending on the functional groups on the polymeric sacrificial material used. The differences in microstructure have been correlated to variations in the chemical reactivity between the sacrificial polymer and the MSQ matrix. Solid-state Si-29 and C-13 nuclear magnetic resonance, and Fourier transform infrared spectroscopy have been used to study the chemical structure of the TMSNB and TESNB: MSQ mixtures. Indications of a chemical bond between the TMSNB and the MSQ have been found in these mixtures; however, the same results were not observed for the TESNB system. The addition of an acid catalyst to the TESNB was found to induce a reaction between the TESNB sacrificial polymer and the MSQ. The percent weight loss of the MSQ and its mixtures (with TMSNB and TESNB) were used to evaluate the polymer residue.