Adjustable pretilt angle of nematic 4-n-pentyl-4′-cyanobiphenyl on self-assembled monolayers formed from organosilanes on square-wave grating silica surfaces

The square-wave grating silica surfaces are fabricated by soft embossing silica sol-gel precursor on glass substrates with an elastomeric polydimethylsiloxane mold. The patterned silica surface could induce the planar alignment of liquid crystal 4-n-pentyl-4(')-cyanobiphenyl (5CB) along the direction of microgrooves but with no pretilt angle. The pretilt angle of 5CBs is adjusted from 0 degrees to 90 degrees by the further deposition of organosilane self-assembled monolayers with different functional end-groups on the patterned silica surfaces.