This presentation exemplifies the latest Power Point dogma'

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This presentation exemplifies the latest Power
Point dogma.
dogma, n. A settled or established opinion,
belief, or principle
A full sentence at the top tells the main point.
Vertically aligned lists are avoided in favor of
diagonal arrangement to create visual tension.
Tasteful use of animation helps.
A page number helps reader ask questions.
Occasionally, put in something strange or fun to
keep professors and other tired listeners awake.
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You cannot measure absolute molecular
weightsDow manager, 1983

• Wrong!
• Correct, even in 1983 you NEED NOT always
  measure ABSOLUTE molecular weightsbut you could
  have.
• Correct in 2005 it is almost always
  essential to measure absolute M s.

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So, how would you analyze polymers and
nanoparticles for polydispersity?
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Here is the easiest equation in this talk.
SEC GPC GFC
Size Exclusion Chromatography Gel Permeation
Chromatography Gel Filtration Chromatography
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A riddle

• After a hurricane, many trees fall over and bend
  into a river. Also, a cow and a dog fall into
  that flooded river. Which one reaches the ocean
  first, cow or dog?

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In GPC, as when throwing a cat through a tree,
the big things come out first..

• Solvent flow carries molecules from left to
  right big ones come
• out first while small ones get caught in the
  pores.
• It is thought that particle volume controls the
  order of elution.
• But what about shape?

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Simple SEC is only simple when you dont have to
do it yourself.
log10M
Ve
pump
injector
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In simple GPC, you first make a map (calibrate),
then follow it.
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Are you straight?
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Use the right tool (column) for the job.
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OK, but how did you get the M values for the
standards?

• Osmometry
• Scattering
• MALDI
• Analytical ultracentrifugation End group
  analysis
• Goal in this class make it seem reasonable that
  it IS possible to measure M values.

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Osmometry is Real Science because it is tied
closely to thermodynamics.
Semipermeable membrane stops polymers, passes
solvent.
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Light scattering operates on thermodynamics
think of it as an osmometer without the membrane.

100,000 ?
x
q
Teaching Light Scattering to Exemplify and
Reinforce Basic Principles, D. S. Poche', P. S.
Russo, B. Fong, E. Temyanko and H. Ricks, J.
Chem. Ed.,  1999, 76 (November), 1534-1538.
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LS adds optical effects ? Size.
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Just add LS detectorand much complexity.
DRI
pump
injector
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This waterfall plot shows many slices of a
chroma-togram 13 angles were recorded 8 times
per second as the sample flowed by the MALS
detector.
Scattered intensity
Scattering angle
Ve
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The scattering envelope for a single slice
shows how Is decreases with angle.
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We add a viscometer in some cases.
LS90o
pump
injector
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Intrinsic viscosity is a secondary molecular
weight method so good its almost like the real
thing.

• Mark-Houwink-Sakurada relationship between the
  intrinsic viscosity and the molecular weight.

K and a are constants for a given polymer, not
strongly dependent on solvent or temperature, as
long as were talking about a good solvent.
These words have special meaning in polymer
science.
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Grubisic, Rempp Benoit, JPS Pt. B, 5, 753 (1967)
Universal Calibration lets you get the molecular
weight of one kind of polymer knowing only the
Mark-Houwink- Sakurada values of a standard (look
it up) and your unknown (uh-oh).
One of of the most important papers in polymer
science. Imagine the work involved! 6 pages long
w/ 2 figures. Selected for JPS 50th Anniv. Issue.
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Universal Calibration says that whatever comes
out at a particular volume has the same product ,
hM.
  ?A?MA ?S?MS f (Ve)
Universal Calibration A analyte S standard
h KM a
Mark-Houwink Relation
Combine to get these two equations, useful only
if universal calibration works!
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They were young when GPC was.
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They were young when GPC hit middle age.
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Here is a small subset of GPC spare parts.
To say nothing of unions, adapters, ferrules,
tubing (low pressure and high pressure), filters
and their internal parts, frits, degassers,
injector spare parts, solvent inlet manifold
parts, columns, pre-columns, pressure
transducers, sapphire plunger, and on it goes
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Other SEC Deficiencies

• 0.05 M salt at 10 am, 0.1 M salt at 2 pm?
• 45oC at 8 am and 50oC at noon?
• Non-size exclusion mechanisms binding.
• Big, bulky and slow (typically 30
  minutes/sample).
• Temperature/harsh solvents no fun.
• You learn nothing by calibrating.
• Columns are expensive, easily damaged.

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Must we separate em to size em?Your local
constabulary probably doesnt think so.
Atlanta, GA I-85N at Shallowford Rd. Sat.
1/27/01 4 pm
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Matrix Fluorescence Photobleaching Recovery is
an LSU-invented method designed to compete with
GPC for certain systems (aqueous commodity
polymers).

• Indicates targeted M.

G. J. Doucet, D. Dorman, R. Cueto, D. Neau, P.
S. Russo, D. DeKee, J. Pople Macromolecules
 2006, 39(26),  9446 9455.
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Ultimate Goal A Black Box for MWD
Press for MWD

• Matrix FPR
• Easily Maintained
• Accurate
• Precise
• Simple Concept
• Expedient
• Easy System Switch
• Basic Info Obtained
• Miniaturizable
• Detect Large Masses
• Labeling Required

• GPC
• Accurate
• Simple Concept
• Miniaturizable
• No Labeling Required
• Broad Distributions
• Pumps
• Parts

DOSY Easy System Switch Precise Accurate Obtain
Basic Info Labeling Required
DLS Form Factor Index Matching Long Acquisition
for Multiangle Experiments Precise Accurate
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In other words, the search continues.

• Two promising contenders are discussed next.
• MALDI-TOF most effective when the molecules are
  small, biological and not very polydisperse. Can
  be coupled to GPC!
• FFF like GPC only a flowing field replaces the
  stationary phase, stuff comes out backwards, and
  big stuff can be handled as well as small.

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MALDI-TOF stands for Matrix-Assisted Laser
Desorption Ionization Time-of-Flight Mass
Spectrometry.
http//www.astbury.leeds.ac.uk/Facil/MStut/mstutor
ial.htm
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These data obtained at LSU click the figure to
analyze these results.
?Guess what Mw/Mn is.
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Patience is a virtue.

• You 4010 students will get to practice with a
  MALDI dataset, but .
• thats enough MALDI for now.

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What about separating cows and elephants? Either
will float around the trees. How do you
separate them then?
Moo!
Eeee!
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Field Flow Fractionation, thats how!
In FFF, large nanoparticles are made to flow
between plates a field is applied to separate
them by size.
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The most commonly used field is flow itself one
or both plates are porous, and a cross-flow is
arranged.
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What happens because of the cross-flow?
Little nanoparticles come out first!

• At LSU, only one plate is porous.
• Everyone calls it AF4 Asymmetric Flow Field
  Flow Fractionation
• How to you get a crossflow then?

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Potential Advantages of FFF

• Handles a wider range of particles.
• May be easier for some aggressive solvents.

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AF4 can even separate large PTFE latex particles.

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Conclusion

• GPC is essential in any Nano Lab
• GPC may eventually get replaced.
• Matrix FPR
• FFF