The effect of alkyl chain length on the structure of pillared carbons prepared by the silylation of graphite oxide with alkyltrichlorosilanes

Pillared carbon was obtained from graphite oxide silylated with alkyltrichlorosilanes with various alkyl chain lengths. The interlayer spacings of silylated graphite oxides became maximal when 1.1–1.5 molecules of bound silyl groups were attached per C8 graphite oxide unit. Pillared carbon with an interlayer spacing of 1.27 nm was obtained only when graphite oxide silylated with methyltrichlorosilane was heated under vacuum above 300 °C. Infrared absorption measurements indicated that the pillars possessed the ladder type silsesquioxane structure. The adjacent graphite oxide layers were connected to each other even before pyrolysis, judging from the observation that n-hexadecylamine was not intercalated. The formation of a ladder type pillar was completed after the oxygen-containing groups were removed from the graphite oxide layers. When the alkyl chain length was longer, the connection of adjacent layers became difficult and pillared carbons were not formed. The surface area of the pillared carbon was very small because the distance between pillars was too small for nitrogen molecules to pass, but it was estimated based on the composition of the pillared carbon.