Dear Pontic,
Thank you for your very perceptive question about this interesting
family of compounds.
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What do Chromacenes do?
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Chromacenes are part of the wider group called metallocenes: A type of
organometallic complex compound in which metal ions are sandwiched
between two or more cyclopentadienyl rings. (The New Penguin
Dictionary of Science)
A representation of a metallocene can be found at the Frequently Asked
Questions page of Advanced Chemistry Development:
An example structure would be Cp2MCl2
Where Cp2 is the cyclopentadienyl anion
And M is one of (Iron, Chromium, Nickel, Cobolt, Vanadium, and
Titanium), hence ferrocene, chromacene etc.
http://www.acdlabs.com/faq/drawing.html
From now on, I shall follow the general practice of referring to
metallocenes rather than the specific Chromacene when referring to
their general use, production and properties.
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There prime industrial use is as catalysts in the production of
polymers and therefore there applications are as wide as the use of
polymers which include: foams, extrusions, moldings, coatings, plastic
film, vehicles, photocopiers and laser discs.
This U.S. Department of Energy, Office of Science document: “Five
Years of Basic Science Accomplishments” highlights their importance:
“The discovery of metallocene catalysts caused major advances in
polymer production (e.g., polyethylene, polypropylene), the most
widespread of synthetic materials. The ability to control the
orientation of each link of a polymer chain allows control of
crystallinity, density, softening point, and other important
properties. A recent improvement in these catalysts is the synthesis
of bimetallic complexes in which two catalytic centers and two
cocatalytic centers are held in close proximity in solution or
adsorbed on surfaces. By altering the nature of the centers, it is
possible to control rate of reactivity, the degree of chain branching,
and plastic rigidity.”
http://www.er.doe.gov/production/bes/BES_Accomp_FY97_FY01.doc
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How are Chromacenes Formed?
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Patent 6,239,300 Describes one possible Metallocene production process
“A number of process steps are provided that can be combined to
produce bridged cyclopentadienyl-fluorenyl metallocenes. The process
steps include production of a cyclopentadiene compound from
dicyclopentadiene; production and recovery of a fulvene compound using
the cyclopentadiene compound; production of a raw metallocene product
using the fulvene compound; and recovery of the pure metallocene from
the raw product. “
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=/netahtml/search-adv.htm&r=4&p=1&f=G&l=50&d=pall&S1=(metallocene.TTL.+AND+production.TTL.)&OS=ttl/metallocene+and+ttl/production&RS=(TTL/metallocene+AND+TTL/production)
OR from makeashortlink.com
http://makeashorterlink.com/?H23813071
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How do they change the frequency of light?
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This description at the University of Hamburg was the simplest
explanation I could locate:
http://www.tu-harburg.de/et7/forschung/optik/optik_e.html
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Also from Unsbo:
“A light wave consists of electric and magnetic fields which vary
sinusoidally at high frequencies. When light propagates through matter
it will therefore induce motion of the charged particles that
constitute the material. In a dielectric medium the charges are bound
together and will start to oscillate in the applied electric field;
they form oscillating electric dipoles.”
I think essentially the asymmetric structure of doped metallocenes
allow them to form strong dipoles in the presence of heat and a static
electric field. Furthermore, this polar alignment is maintained
following cooling.
“…For low light intensities, i.e. small amplitudes of the electric
field E, the charges can follow the field almost exactly and the
relationship between E and P is essentially linear. For larger
amplitudes the motion of the particles will be distorted and nonlinear
terms will be important.” (Usbo)
Ie frequency doubling and tripling
Additionally, their ease of fabrication, stability, transparency and
other physical characteristics qualify them as excellent candidates
for the creation of non-linear optical devices. However, as the papers
below state, there are still problems to solve.
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Can they be found on the surface of stainless steel?
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I understood this to mean, can chromasene catalyzed polymers be found
on the surface of stainless steel. The answer is yes, the polymers can
be applied to a wide range of surfaces. One of the applications using
stainless steel I noticed was medical catheters. However, I would be
happy to provide more detail of any specific application. Your
question seemed to indicate that you had a particular application in
mind. If you let me know by selecting “clarify answer” I would be
happy to provide further details.
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Links:
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The New Penguin Dictionary of Science:
http://www.xrefer.com/entry/642890
A Dictionary of Science, Oxford University Press
http://www.xrefer.com/entry/490158
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Other links:
This Kenrich Petrochemicals, Inc. document lists many advantages of
metallocene catalyzed polymers:
“…Metallocene-like titanium catalysis provides greater strength,
regeneration and copolymerization - allows more regrind. 1% CAPS®
L12/L gives up to 20% faster extrusion, injection & blow molding at
10% lower temperatures. Other benefits are: adhesion promotion:
phosphato flame retardance: dispersion; hydrophobicity;
anti-corrosion; and finer foam cell structure.”
http://www.devicelink.com/expo/plast01/matsupl.html
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Despite its significance, metallocene catalyzed polymers only
accounted for 1% of the polymer market at the time of this article by
Polymer Age of June 26, 2000:
“metallocene materials was up by 30 per cent - although they still
only represent around 1 per cent of the total market.”
http://www.polymer-age.co.uk/archive28.htm
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Long, Nicholas, Imperial College of Science Technology and Medicine,
notes:
“We are designing new new precursors, featuring metallocene and/or
transition metal fragments and conjugated organic units such as
alkynes and vinylidenes, that can undergo polymerisation. There is
great potential application of these materials, especially as
molecular wires and switches and in the field of nonlinear optics. We
have produced small donor-acceptor type systems which potentially have
second-order non-linear optical properties (where the frequency of
light is doubled) but have concentrated on longer chain or
mixed-valence p-delocalised species to act as third-order non-linear
optical materials (trebling the frequency of light).”
http://www.ch.ic.ac.uk/long/nlresin.htm
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Very detailed review of compounds with non-linear optical responses:
Thierry Verbiest,* Stephan Houbrechts, Martti Kauranen, Koen Clays and
Andre´ Persoons, "Second-order nonlinear optical materials: recent
advances in chromophore design"
http://perswww.kuleuven.ac.be/~p1005260/JMaterChem1997.pdf
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Unsbo, Peter, Non-linear Optics:
http://www.optics.kth.se/fysik2/staff/pu/thesis/node19.html
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Search Strategies:
Chromascene OR chromasene
Metallocene formation
Metallocene “stainless steel” bonding resin
Metallocene structure
metallocene light properties
metallocene light frequency doubling
Patent database, then within the database :
Chromascene OR chromasene
Metallocene
Metallocene production
[Thanks also to pinkfreud for the spelling suggestion]
Naturally, I would be happy to elaborate or clarify any of the above.
Please just select clarify answer to provide guidance.
Regards, |
