Transcript Jello
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