Bicontinuous Nanoporous Plastics Marc Hillmyer University of Minnesota DMR0094144

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Bicontinuous Nanoporous Plastics Marc Hillmyer
University of Minnesota (DMR-0094144)
Block copolymers are excellent precursors to
nanoporous materials.1 Selective chemical etching
of the minority component in a self-assembled AB
diblock copolymer results in a nanoporous version
of the majority component. We have demonstrated
this in cylinder-forming polystyrene-polylactide
(PS-PLA) diblock copolymers using PLA as the
etchable block.2 We showed that orientation of
the cylinders was required for the generation of
macroscopic nanoporous samples. Etching of the
gyroid morphology has been more challenging due
to limited regions of stability in the AB diblock
morphology diagram. Recently, we have shown that
by vitrification of a PS-PLA diblock copolymer
that forms the gyroid phase at high temperatures,
this interesting bicontinuous morphology can be
trapped at room temperature. Subsequent
degradation of the PLA component by chemical
etching (with aqueous HI) gave nanoporous PS
monoliths with bicontinuous channels.3 These
materials may prove to be very useful in
applications associated with selective
separations and nanomaterial templating. 1
Hillmyer Adv. Polym. Sci. in press. 2 Zalusky et
al. J. Am. Chem. Soc. 2002, 124, 12761. 3 Mao and
Hillmyer, unpublished results.
polystyrene
Cartoon of a nanoporous gyroid sample
nanochannel
Scanning electron microscopy image of a
nanoporous PS sample with the gyroid morphology
Small-angle X-ray scattering data for a PS-PLA
sample with the gyroid morphology before (black)
and after (red) etching