Magnetically induced orientation of mesochannels in 2D-hexagonal mesoporous silica films

Mesoporous silica films with uniaxially oriented mesochannels were prepared by dip coating under a steady-homogeneous magnetic field parallel to a substrate. The effect of a strong magnetic field ( 12 Tesla) on the preparation of mesoporous silica films was systematically investigated by using two kinds of templates. When mesoporous silica films with a 2D-hexagonal structure were prepared by using an ionic CTAB ( hexadecyltrimethylammonium bromide)-based precursor solution, the in-plane XRD results of the films proved that the mesochannels were slightly oriented parallel to the magnetic field. When mesoporous silica films were prepared by using a non-ionic P123 ( polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer)- based precursor solution, the directional distribution of the mesochannels became narrow (FWHM was about 20 degrees). The use of large molecules such as triblock copolymers leads to successful magnetically induced orientation. The spatial orientations of the magnetically aligned mesochannels are elucidated by theta - 2 theta XRD, in-plane XRD, cross-sectional transmission electron microscopy (TEM), and high resolution scanning electron microscopy (HR-SEM).