Chiral organic-inorganic hybrid silicas can be prepared via the self-assemblies of chiral surfactants and gelators as templates.However,the relationship between the chirality of the hybrid silica and the structure of the surfactant/gelator has not been systemically studied.Herein,a series of chiral low-molecular-weight amphiphiles（LMWAs） derived from L-valine was synthesized.Their alkyl chains were n-butadecyl,n-hexadecyl and n-octadecyl,respectively.They can form viscous liquids in pure water,and physical gels in tetrahydrofuran,cyclohexanone,acetonitrile,acetone,chlorobenzene and nitrobenzene.Chiral 1,4-phenylene-silicas were prepared via the self-assemblies of these LMWAs as templates.With increasing the alkyl chain length,the 1,4-phenylene-silicas changed from short mesoporous nanorods to long nanotubes.The circular dichroism spectra of the 1,4-phenylene-silicas indicated that the long nanotubes exhibit the strongest chirality.
XIAO MinLIU Xiao-juanHU KaiWU Li-minLI YiLI Bao-zongYANG Yong-gang
Single-handed helical silica nanotubes were prepared according to the literature procedures,using the self-assemblies of a pair of chiral cationic low-molecular-weight gelators as the templates.A chirality indicator,4,4＇-bis（triethoxysilyl）-1,1＇-biphenyl,was developed to determine the chirality of the silica nanotubes.The chirality of the surfaces and the bulky walls of the silica nanotubes were understood from the twist of the biphenylene rings.
Helical 1,2-ethylene-silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like mesopores inside were prepared according to literature procedures. After carbonization, helical carbon/ silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like micropores inside were obtained. The morphologies and pore architectures of the carbon]silica nanofibers were characterized using transmission electron microscopy, field-emission scanning electron microscopy, powder X-ray diffraction and N2 sorptions. Although the mesopores inside shrank into micropores, the helical nanostructure remained. Moreover, several carbon/silica nanofibers with lamellar mesopores on the surfaces and concentric circular micropores inside were also obtained. After being calcined in air, helical silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like micropores inside were produced as well.
Multilayered 1,2-ethylene-silica nanotubes were prepared with cetyltrimethylammonium bromide（CTAB） as a template and（S）-β-citronellol（CN） as a co-structure-directing agent.For a better understanding of the formation of this structure,the CN/CTAB molar ratio in the reaction mixtures was tuned.With increasing the CN/CTAB molar ratio,a hexagonal to lamellar phase trasformation was observed;and the morphologies of 1,2-ethylene-silica changed from rod to vesicle and then to tubular structure.CN droplets were proposed as the templates for the nanotubes.The obtained samples were characterized by means of X-ray diffraction,nitrogen sorption,field emission scanning electron microscopy and transmission electron microscopy.
