Abstract
Two chiral hydrogelators, L-18ValPyBr and D-18ValPyBr, composed of L- or D-valine, were synthesized.
They self-assembled into thin membranes under high concentration and helical nanofibers under low concentration in
pure water. Sol-gel transcription reactions were carried out under both acidic and basic conditions using the selfassemblies
of these two gelators and the mixtures with CTAC as templates and TEOS as precursor. Under acidic
conditions, minimum gel concentrations of L-18ValPyBr and D-18ValPyBr are very low. After sol-gel polymerization,
a kind of cotton-like silica constructed by twisted mesoporous silica ribbons was obtained. These ribbons were 60 nm in
width and 10 nm in thickness. Under basic conditions, both mesoporous twisted ribbons and nanotubes constructed by
tightly coiled ribbons were obtained. Generally, left-handed helical structures were obtained by using L-18ValPyBr,
while right-handed helical structures were obtained by using D-18ValPyBr. The morphologies were sensitive to the
concentration of NH3. When the concentration of NH3 was 2.5 wt%, twisted ribbons were obtained. When the
concentration of NH3 was higher than 5.0 wt%, nanotubes constructed by tightly coiled ribbons were obtained.
Mesoporous silica structures in nano- and micro-size were prepared by using the mixtures of L-18ValPyBr and CTAC
under both acidic and basic conditions. Under acidic conditions, helical mesoporous fibers were obtained, and their
diameter was increased with increasing the ratio of CTAC to gelator. The nanofibers obtained under basic conditions
were shorter than those obtained under acidic conditions. The mesoporous channels were parallel each other and
running along the axis of nanofibers.
