Chemistry Reference
In-Depth Information
materials have been based on functionalized PDMS and lanthanide
ions,
355
or CdSe quantum dots.
356
Other unusual additives include oxetanes,
357
vinylic macromono-
mers,
358
silicon carbide,
359
superconductive carbon blacks,
360
silver-coated
fly ash,
361
metal oxides,
362
Tb
3+
for green emission,
363
antibacterial
agents,
364
and organic-inorganic hybrid copolymer fibers.365
365
In an inter-
esting reversal, transition element acetylacetonate salts were decomposed
in a PDMS matrix to give membranes with catalytic activity.
366
Porous materials, including aerogels and xerogels,
30,
31
can be synthesized
in cylindrical, hexagonal, or monoclinic
367
and hierarchically ordered
structures.
368,
369
Methods have been developed to prepare hybrid silica-
silicone PDMS nanofibers370
370
and nanocapsules that are hollow and have
controlled diameters.
371-373
Some polysiloxane capsules can be deformed
by external electric fields.374
374
PDMS sheets bombarded with gallium ions
form skins that are under strains not experienced by the underlying poly-
mer.
375
This strain causes a wrinkling into wavy or hierarchical patterns.
Gold films can also be used for this purpose.
278
Such materials could be
useful in microfluidic devices, for example, for mixing and stretching pro-
teins and polynucleotides.
An origami type of structure can be obtained by placing a droplet of a
liquid such as water on a sheet of PDMS placed on a superhydrophobic sur-
face.
376
Capillary forces then wrap the PDMS sheet around the droplet.
Square sheets of PDMS envelope the droplet in a cylindrical shape, while
triangular sheets seal it into the shape of a tetrahedral pyramid.
Replication techniques are available for transforming complex silica
shapes into the corresponding shapes of various polymers.
377
he process
can also be extended in the opposite direction, by converting the silica
into silicon. Specifically, a low-temperature reduction process has been de-
veloped to convert three-dimensional nanostructured silica micro-assem-
blies into microporous nanocrystalline silicon replicas.
378
Such materials
could be useful in a variety of applications, including sensors and biomedi-
cal devices.
Monte Carlo computer simulations have been carried out on a variety of
filled elastomers, including PDMS,
379-382
in an attempt to obtain a better
