Abstract Unique mesoporous silica materials are synthesized with different straight chain alkanes, n-dodecane, n-decane and n-hexane. As swelling agents, these straight alkanes exhibit comparable swelling effect on the nano-sized channels of these mesoporous silica materials and thus the pore size of these silica materials varies in a narrow range from 10 nm to 12 nm. However, these straight chain alkanes result in variable mesostructures and morphologies of final products, reflecting remarkable different self-assembly routes for the P123 micelles in different P123–H 2 O–alkane systems. Silica nanotube bundles can be obtained with n-dodecane while hexagonally ordered silica material in alternating and bumpy morphology is synthesized with n-decane. If n-hexane is used, mesostructure cellar foam is successfully synthesized.