• make a new phase of carbon, called linear carbon• explosion in laboratory at Allied Chemical• injury and the end
Others persistedlinear carbon is now coming closer to possiblesuccess
The story started from….• Heeger, McDiaramid, and Shirakawas discovery of conducting behavior in doped polyacetylene samples
Application nowadays• photovoltaic cells• field-effect transistors• chemical sensors
From Harvard University Digital Library for Physics and Astronomy• Improved photovoltaic cells and electrodes for use therein, particularly electrodes employing amorphous silicon or polyacetylene coating are produced by a process which includes …….. http://adsabs.harvard.edu/abs/1983doe..reptV....S
From Harvard University Digital Library for Physics and Astronomy• Planar and sandwich types of polyacetylene metal-semiconductor field- effect transistors (MESFETs) have been fabricated. http://nina.ecse.rpi.edu/2dfet/images/ntype2_big.gif http://adsabs.harvard.edu/abs/1991JaJAP..30.2101C
Chemical Sensor• Polyacetylene based nonlinear optical material prepared by ring-opening metathesis polymerization of cyclooctatetrene derivatives.
Polyphenylenevinylene• Main material of Polymer Light Emitting Diode(PLED) http://www.euso.be/euso/home/images/test2.pdf
Polydiacetylenes• applications in optical limiters, waveguides, and thermometric sensors
Special properties• per-chain stiffness close to diamond• high coefficients for tripling the frequency of incoming light• negative thermal expansion coefficients tunable to near zero by introducing defects
Most Application• printed inks containing diacetylene microcrystals have been used as time- temperature indicators
Mechanism• Diacetylenes typically have an actuation energy for thermal polymerization of about 20 to 28 kcal/mol, which can be tuned to closely match the activation energy and degradation rate for important perishables
Good color indicator• Color changes of the diacetylene microcrystals during thermal polymerization provide a visual indication of whether a perishable product in the same thermal environment has degraded as a result of integrated time-temperature exposure
• Over a billion of these diacetylene polymerization-based indicators have been used on individual vaccine vials since 1996 to assist disease eradication in parts of the world that do not have a reliable cold chain
• The United States Army is using these diacetylene indicators on cartons of their MREs (Meals Ready to Eat)
Explosive compound• Though the advantages mention before, there is a problem on synthesis Polydiacetylenes• With increasing n, crystals comprising only polyynes--that is, R − (C ≡ C) n − R molecules-- become increasingly unstable, unless R is a bulky substituent group
Dangerous…..• At room temperature, it can explode if subjected to physical shock, and it decomposes slowly under ambient light, forming an insoluble material with a graphite-like appearance
Solution?• Poly(diiododiacetylene), or PIDA represents a possible solution to the general problem of polydiacetylene synthesis
Why is it?• The abundance of transition metal–catalyzed reactions available for adding substituents in place of a carbon-halogen bond makes PIDA a potential precursor to a wide variety of polydiacetylenes.• Sn2 Sn1 − δ− Nu + C X C Nu + X− δ+ δ− + δ C X C + X− − C + Nu C Nu Organic Chemistry Bruice
A complex compound• C4I2 is complexed with a specially chosen agent, an oxalamide. In these crystals, 1,4-addition polymerization of diacetylene occurs spontaneously to produce single crystals of the complexed polydiacetylene
Getting Better• The complexing agent appears to stabilize the polymerized C4I2 against explosive decomposition and eliminates the type of disorder
Disorder comes from nature• Disordered along the direction of the molecular axis. In these crystals, the alignment between adjacent monomers is random, preventing ordered polymerization
Problem caused from disorder• Obtaining the desired optical and electronic properties of a given conjugated polymer requires a highly ordered molecular structure
Way to solve the problem• if the diynes are first aligned appropriately in the solid state at a distance commensurate with the repeat distance in the target polymer, then their arrangement in space will control their reactivity, leading to ordered topochemical polymerization
Best distance• Distance of 4.9A is highly preferable for the aligned dynes with target to form highly order structure.
Conclusion• With all the efforts to make the polydiethylene mentioned before, we shall have a blueprint on how could these material be utilized and how to make it real.
• Whether or not linear carbon synthesis is practical by the poly(C4I2) route, the idea with using poly C4I2 has provided both an exciting new electronic material and a route that could lead to novel related and derivative materials.
References• Dangerously Seeking Linear Carbon Ray H. Baughman Science mag Vol. 312. no. 5776, pp. 1009 - 1110• Preparation of Poly(diiododiacetylene), an Ordered Conjugated Polymer of Carbon and Iodine Aiwu Sun, Joseph W. Lauher, Nancy S. Goroff Vol. 312. no. 5776, pp. 1030 - 1034• Harvard University Digital Library for Physics and Astronomy• Organic Chemistry ver 4 BruiceOriginal Image Source:( Images used in this PowerPoint are modified by Stan Yang)http://stc-mditr.org/research/oeoaomd/projects/2.2.1.cfmhttp://nina.ecse.rpi.edu/2dfet/images/ntype2_big.gif