on Nanoporous Membrane
Graduate School of Material Science, NAIST
This is an abstract
for a poster to be presented at the
Foresight Conference on Molecular Nanotechnology.
The full paper is available here.
Various types of nanoporous materials have been developed.
Here polyelectrolyte brushes were grafted on a nanoporous
membrane to regulate the substance permeation through the pores
in response to pH, temperature, oxireduction, or
photo-irradiation. The conformation of polyelectrolyte chain is
dependent upon the environmental conditions. In the case of
poly(acrylic acid) grafting, the polymer chain is protonated and
contracted in the regions of low pH; it is de-protonated and
extended in regions of high pH. Therefore, the size of each pore,
and thus the permeability through the membrane could be rapidly
regualted by changing the pH change because the brush chains
directly contact with environment.
In order to graft the polyelectrolyte chains to the surface,
track-etch porous polycarbonate membrane (average pore diameter,
200 nm) was glow-discharged and poly(acrylic acid) was
graft-polymerized on the membrane surface. The water permeation
rate through the grafted membrane was high at low pH, but was
reduced at neutral pH. These changes in permeation were
reversible upon additional pH changes. To clarify the mechanism
of permeability regulation of the polyelectrolyte brush system,
an atomic force microscope was used to make and in situ
observation of pore shape in an aqueous solution. The presence of
pore was observed at low pH, but not at high pH. Thus the
polyelectrolyte grafts behave like a gate to open and close the
pores. In addition, in this system, the change in permeability
change occurred within several seconds of pH change. The
polyelectrolyte brushes were put in direct contact with their
environment; this allowed them to respond quickly.
Yoshihiro Ito, Graduate School of Material Science, NAIST, 8916-5
Takayama-cho, Ikoma 630-01, JAPAN, ph: +81-743-72-5903,
fax:+81-743-72-5903, email: firstname.lastname@example.org