Jello
•
Polymer: Gelatin
– Protein collagen from skin, bones and
connective tissue
•
Thermoreversible
– natural state, collagen exists as fibers that
contain three polypeptide chains entwined
into a helical structure.
– Upon heating the relatively weak
(noncovalent) bonds holding the three
polypeptides together break down,and some
of the stronger, covalent bonds, and produces
a solution in which the polypeptides are
arranged into an amorphous structure
Jello
•
Thermoreversible (cont.)
–
–
–
gelatin cools below a certain
temperature, the molecules tend to
associate to regain some of their
original helical structure. Junction zones
form, local regions return to the original
form: three polypeptide chains in a
helical formation
Junction zones are capable of entraining
large amounts of water.
If the gel is reheated, it will convert
back to a liquid because the forces
favoring the amorphous state (mainly
configurational entropy) outweigh those
favoring the aggregated state (mainly
hydrogen bonds)
Above is an example of a nanoporous polymer/inorganic hybrid material, which exhibits the
synergistic properties of organics and inorganic materials. The polymer-carbon hybrid materials
exhibit the same chemical properties of the organic polymers while the pore stability against
mechanical compression, thermal and chemical treatments is greatly enhanced. The resultant
materials, exhibiting the surface properties like organic polymers, maintains almost the same
electric conductivity of the carbon framework. The synthesis strategy can be extended to various
compositions of hydrophilic and hydrophobic organic polymers
http://rryoo.kaist.ac.kr/res-3.html
Photonic Crystals
•Photonic crystals are periodic dielectric structures that have a band gap that
forbids propagation of a certain frequency range of light.
•This property enables one to control light with amazing facility and produce
effects that are impossible with conventional optics.
•Sub-micrometer spheres assembled in the laboratory are referred to as synthetic
opals derived from sub-micrometer colloidal spheres (silica or polymer), which
can be induced to spontaneously organize on a crystalline lattice.
•By using the synthetic opal as a template a much more interesting photonic
crystal can be made, the so-called inverted opal, which is a replica of the original
opal.
•Photonic crystal can be used for optical communications, interconnects for
optical circuits, photonic-crystal fibers, waveguide intersections, etc.
SEM image for periodic structure assembled from PMMA
(poly(methyl methacrylate)) spheres