Fourier transform infrared (FTIR) spectroscopy, contact angle, and electrical measurements were used to study porous methylsilsesquioxane (p-MSQ) films (JSR LKD 5109) processed with alkylmonochlorosilanes having chain lengths of one to eighteen carbon atoms dissolved in supercritical carbon dioxide at 155-185 atm and 55-60°C to repair oxygen ashing damage. The FTIR results showed that all chemistries reacted with silanol groups on the surface of the pores producing covalent Si-O-Si bonds. Self-condensation between the alkylsilanols with chain lengths above four carbon atoms produced a physisorbed residue, which was partially removed after rinsing with pure SCCO2. The hydrophobicity of the blanket p-MSQ surface was recovered, while the initial dielectric constant of 2.4 for the blanket p-MSQ surface was restored after treatment. With an increase in the length of the alkyl chain, the contact angle increased from 84° to 108° and the dielectric constant measured on metal-insulator-semiconductor capacitors was approximately constant in the range 2.4 ± 0.05. The monochlorosilanes restore the dielectric constant and surface properties of mesoporous p-MSQ and are candidate pore sealing additives.