re: plastic magnets lead to cheap MRI??
vedr: ny plasticmagneter fører til billigere hjernescanning?
the original article was published in: Science, 2001, 294, 1503 "The
first pi-conjugated organic polymer magnet"
I have included some article references with chemical diagrams
scott@...
webposted 14.12.2001

Team Has 2 Words: Plastic Magnet
By Louise Knapp

2:00 a.m. Dec. 13, 2001 PST

The world's first organic polymer magnet has just made its debut;
soon, you may be able to scrap those metal magnets and
pull out a plastic version.

A team of scientists from the University of Nebraska has finally
managed to translate a theory they had been trying to prove
for 13 years into a working reality.

"It is a very challenging project but one that we thought was
feasible," said Andrzej Rajca, head of the project and
professor in the department of chemistry at the University of
Nebraska-Lincoln. (http://www.chem.unl.edu/)

The result is a piece of plastic that not only packs magnetic pull,
but is also cheaper and lighter than its metal
counterpart.

Its strongest attraction, however, is its flexibility. "It's a much
more malleable material," Rajca said.

"It's very hard to make a thin film out of metal and it is a very
expensive process, but plastic can be molded into any
shape."

Clifford Nickel, director of research at the Advanced Magnetic
Research Institute of North Carolina, studies the use of
magnets in medicine.Magnets have been used therapeutically in
medicine for nearly 2,000 years.

Iron atoms in red blood cells are believed to respond to magnetism.
When a magnet is placed on a patient's body, blood
flow through the area is enhanced.

Nickel believes the flexibility of Rajca's plastic magnet would make
it a useful tool in his field.

"You could tape it to the base of the skull or shoulders to treat
migraines. Where a metal magnet block would stick out
of your clothes, this would not," Nickel said.

But the plastic magnet in its current form also comes with a whopping
disadvantage: It only works in temperatures of 440
degrees below zero Fahrenheit.

The plastic magnet consists of an organic polymer made up of carbon
and hydrogen that has various electronic properties.

"One of the important characteristics of the material is that it is
arranged in such a way to give a number of unpaired
electrons. When aligned, these give rise to magnetic properties,"
Rajca said.

These unpaired electrons only align when they are in low temperatures;
higher temperatures produce a thermal motion that
disrupts the interaction and alignment of the unpaired electrons.

This isn't the only problem.

Organic magnets already exist, but they are based on crystals of small
molecules. "Unpaired electrons interact a lot more
strongly in a polymer than in a crystal or material consisting of
small molecules," Rajca said.

But the magnetic field they produce is still not as strong as their
metal counterparts.

"One disadvantage is that it won't have as many unpaired electrons per
volume that metal has," Rajca said.

"In iron, for instance, there are two unpaired electrons per atom. In
a plastic magnet, you only have one unpaired electron
per dozen atoms."

This means that the magnetic moment per volume, or the total
magnetization, in a plastic magnet will be lower than in a metal
magnet.

"A plastic magnet would have to be big to achieve the necessary
magnetic field, and the application often calls for a small
magnet," Nickel said.

Rajca, however, is confident that these problems can be overcome.

"If we can make the alignment between the unpaired electrons stronger,
then it will be able to withstand the thermal
disruption and have a stronger magnetic field," Rajca said.

Once these hurdles have been crossed, the plastic magnet can go into
production.

Rajca said it is difficult to speculate on applications for the
magnet, as the exact nature of the material is yet to be
determined.

"Most likely, it will be used for high-tech applications -- computer
memory devices -- not in electric motors or transformers
or for something you would put on your fridge," Rajca said.

Rajca did admit, however, that it will be a while before they produce
a practical material.

"It's difficult to predict how long. If we have a major breakthrough,
then it could be very soon, but who can tell?" Rajca
said.

See also:
Cheap Magnets Equal Cheap MRI
How 'Doing It' Is Done
New Armor for Magnetic Devices
Tinker around with Gadgets and Gizmos

Next Up: Magnetic Storms
Jan. 3, 2000

Custom-Made Body Parts
July 5, 1999

Power Lines Posing Health Risks
July 17, 2001

re: references from UNL website:
"searching for organic magnets" (with diagrams)
http://wwitch.unl.edu/rajca/rajcahome.html
the official press release from UNL:

Friday , December 14, 2001

Our research is in the area of Organic Chemistry with emphasis on the
design,
synthesis and study of molecules with novel molecular structure and
chemical
properties. We are interested in fundamental aspects of electronic
structure and its
dependence on the size ranging from fraction of nanometer to several
nanometers.
The objective is to prepare new class of organic materials with
magnetic, conducting and optical properties.
=

We are working on the preparation and =

investigation of very high spin organic =

molecules and polymers. This work is =

important to the understanding of organic =

magnetism and to the quest for organic =

magnets. Numerous very high spin organic =

molecules and polymers with dendritic and =

macrocyclic structures have been prepared by =

our research group. Follow this link to see =

their structures.

Recently, we reported preparation and
magnetic properties of an organic pi-conjugated =

polymer with very large magnetic moment =

(approximate average S = 5000) and magnetic =

order at low temperature (about 10 K). This is =

the first report of a pi-conjugated organic =

polymer magnet (Science, 2001, 294, 1503).

In the area of organic conductors, our
efforts are aimed at the synthesis and study
of chiral pi-conjugated molecules and polymers, precursors to organic
chiral
semiconductors/conductors. The target
molecules include molecules related to a
hypothetical allotrope of carbon
(3-dimensional graphite) and sulfocarbons
(CnSm). A number of chiral organic molecules with interesting
molecular
structure and properties are being prepared in our research group.

Chiral pi-Conjugated Molecules and Polymers


Many molecules and a few polymers with intrinsically chiral
pi-conjugated system are known. However, the traditional approach to
pi-conjugated polymers and small
donor/acceptor molecules, directed at interesting material properties,
is based on attaching chiral non-pi-conjugated pendants to the
approximately planar pi-conjugated system of
polymers and small donor/acceptor molecules. An alternate approach
may rely on introducing pi-conjugated chiral group, such as chiral
binaphthyls or tetraphenylenes, as part of the
polymer chain or network.

Organic conductors, superconductors, and magnets are based on
electroactive pi-conjugated molecules and polymers. For planar
pi-conjugated systems, the material properties
are typically limited by weak intermolecular interactions in 3D.
Electrical conductivity of many organic polymers strongly depends on
orientation/order of polymer chains; in particular,
p-stacking of molecular/oligomeric/polymeric radical ions appears to
play an essential role. Transition temperatures for organic magnets
and superconductors were greatly improved with
the advent of fullerene, replacing the pancake-like planar
pi-conjugated systems.

Typical p-stacks, involving planar pi-conjugated molecules, are
reminiscent of "stacks of pancakes". Tetra-o-phenylenes may be viewed
as four such "
pancakes" arranged in a double helical segment, rigidly fixed at 60
degree dihedral angles and pointing in four different directions.
Extended helices or double
helices may enhance properties derived from chirality (chiral
currents, chiral optical properties) and serve as platforms to orient
pendant groups.
Based upon this concept, our research group has prepared various
chiral tetra-o-phenylene derivatives, including the octaphenylene,
which is the first
molecule with double-helical pi-conjugated system. In addition,
biphenylene dimers, molecular fragment of a 2D carbon net were
prepared.

selected publications:
The first pi-conjugated organic polymer magnet =

(Science, 2001, 294, 1503)

A. Rajca, J. Wongsriratanakul, S. Rajca, "Magnetic Ordering in an
Organic Polymer", Science, 2001, 294, 1503.

A. Rajca, H. Wang, P. Bolshov, S. Rajca, "Greek Cross Dodecaphenylene:
Sparteine-Mediated Asymmetric Synthesis of Chiral D2-Symmetric
p-Conjugated
Tetra-o-phenylenes, Tetrahedron, 2001, 57, 3725-3735.

A. Rajca, Very High-Spin Organic Polymers, Polymer News, 2001, 26,
43-47 (Feature Article).

A. Rajca, H. Wang, V. Pawitranon, T. J. Brett, J. J. Stezowski,
Synthesis and Structure of Tetrathiophene with a Chiral
1,1'-Binaphthyl Kink", Chem. Commun.,
2001, 1060-1061.

A. Rajca, S. Rajca, J. Wongsriratanakul, C. R. Ross, II,
"4,6-Bis-(trifluoromethyl)-N,
N'-di-tert-butyl-1,3-phenylenebis(aminoxyl) and its
Bis(trifluoroacetylacetonato)manganese(II) Complex: Synthesis, X-ray
Crystallography, and Magnetism", Polyhedron, 2001, 20, 1669-1675.

S. Rajca, A. Rajca, "Polyarylmethyl Polyradicals as Organic Spin
Clusters", J. Solid State Chem., 2001, 159, 460-465

A. Rajca, "Organic Spin Clusters, Fractals, and Networks with Very
High-Spin", in Hyper-structureed Molecules III, H. Sasabe, Ed., Gordon
and Breach, in press.



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