Morphology and water barrier properties of organosilane films: the effect of curing temperature.

The morphology of silane films and the response of these films to water vapor are studied by neutron reflectivity, X-ray reflectivity, ellipsometry, and contact angle. The systems studied include bis-[3-(triethoxysilyl)propyl]tetrasulfide (bis-sulfur) and bis-[trimethoxysilylpropyl]amine (bis-amino), as well as mixtures of these two silanes. The effect of curing temperature on water-barrier properties is determined by comparing data for films cured at 180 degrees C with existing data for films cured at 80 degrees C. Higher curing temperature leads to an increase of the crosslink density as well as chemical modification for the sulfur-containing films. For bis-amino silane films, on the other hand, the effect on the water-barrier ability is negligible. Bis-amino silane is fully hydrolyzed and condensed at the curing temperature of 80 degrees C, so further increasing cure temperature does not affect the bulk structure of the film. For bis-sulfur and mixed films, however, higher curing temperature accelerates the hydrolysis and condensation, leading to denser films with better water-barrier performance.