This presentation exemplifies the latest Power Point dogma.

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A full sentence at the top tells the main point.

Vertically aligned lists are avoided in favor of diagonal arrangement to create visual tension.

A page number helps reader ask questions.

Tasteful use of animation helps.

Occasionally, put in something strange or fun to keep professors and other tired listeners awake.

dogma, n. A settled or established opinion, belief, or principle

“You cannot measure absolute molecular weights”Dow manager, 1983Wrong!

Correct, even in 1983: you NEED NOT always measure ABSOLUTE molecular weights…but 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?

Here is the easiest equation in this talk.

SEC = GPC = GFCSize Exclusion Chromatography

Gel Permeation ChromatographyGel 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?

Moo!

Woof!

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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 don’t have to do it

yourself.

degas

pump

injector

DRIVe

log 10

M

c

c

log 10

M

c

log10M7

In simple GPC, you first make a map (calibrate),

then follow it.

Ve

log M

Vo

Ve

logM

A

DRI

VeA

DRIA

MA

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Are you straight?GPC Calibration

log(Mw ) = 0.0009Ve3 - 0.0534Ve

2 + 0.6303Ve + 6.8161

R2 = 0.9996

0

20

40

60

80

100

120

14 16 18 20 22 24 26 28

Ve [mL]

Det

ecto

r R

espo

nse

0

1

2

3

4

5

6

7

8

log(

Mw)

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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?

• OsmometryScattering

MALDIAnalytical ultracentrifugation

End group analysisGoal 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.

h V = n R T

n = g/M

c = g/V

= c R T ...)1

( 2 cAM

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Light scattering operates on thermodynamics; think of it as an osmometer without the membrane.

100,000

x

c

...)21

( 2,

1

cAM

cRTc

IpT

s

q

2

)2/sin(π4 o

nq

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.

q = 0 in phase Is maximum

q > 0 out of phase, Is goes down 3

122g

s

RqI

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Just add LS detector…and much complexity.

degas

pump

injector

DRI

DRI

MALLS

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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.

3D Plot - PBLG

4 5

6 7

8 9

10 11

12 13

14 15

16 Scatterin

g angle

Ve

Scattered intensity

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The scattering “envelope” for a single slice shows how Is decreases with angle.

0.0 0.2 0.4 0.6 0.8 1.00

20000

40000

60000

80000

100000

120000

140000

c = 0.044 mg/mLM = 130000 g/mol

R/K

c

sin2( /2)

InterceptMolecular weight

SlopeSize

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We add a viscometer in some cases.

degas

pump

injector

DRI

LS90o

P viscometer

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Intrinsic viscosity is a secondary molecular weight method so good it’s

almost like the real thing.Mark-Houwink-

Sakurada relationship between the intrinsic viscosity and the molecular weight.

aKM][ K and a are constants for a given polymer, not strongly dependent on solvent or temperature, as long as we’re talking about a “good solvent”.

These words have special meaning in polymer science.

aKM /1)/]([

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Grubisic, Rempp & Benoit, JPS Pt. B, 5, 753

(1967)

One of of the most importantpapers in polymer science.Imagine the work involved!6 pages long w/ 2 figures.Selected for JPS 50th Anniv. Issue.

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).

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Universal Calibration says that whatever comes out at a particular volume has the same product , []M.

[] = KM a

 

[]AMA = []SMS= f

(Ve)

11 SA aSS

aAA MKMK

Mark-Houwink Relation

Universal Calibration A = analyte; S = standard

Combine to get these two equations, useful only if universal calibration works!1

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AS

S

a

A

aS

A K

MKM

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They were young when GPC was.

They were young when GPC hit middle age.

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 doesn’t think so.

Atlanta, GAI-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.

1000 10000 100000 10000000.0

0.2

0.4

0.6

0.8

1.0

Pullulan, 8% HPC Solution, M=12,200 and 48,000

CONTIN Exponential Exponential

FA

rbitr

ary

Un

its

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 Ultimate Goal: A Black Box for MWDMWD

Matrix FPREasily Maintained

AccuratePrecise

Simple ConceptExpedient

Easy System SwitchBasic Info Obtained

MiniaturizableDetect Large MassesLabeling Required

GPCAccurate

Simple ConceptMiniaturizable

No Labeling RequiredBroad Distributions

PumpsParts

Press for MWD

DLSForm Factor

Index MatchingLong Acquisition for

Multiangle ExperimentsPrecise

Accurate

DOSYEasy System Switch

PreciseAccurate

Obtain Basic InfoLabeling Required

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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/mstutorial.htm30

These data obtained at LSU: click the figure to analyze

these results.

0 2000 4000 6000 8000 10000 12000

0

100

200

300

400

File will download from the websiteCompute Mn,Mw,Mz MANUALLYCompute Mn,Mw,Mz in Excel or something elseYou can subtract the mass of silver from each peakWe hope Dr. Tracy McCarley will give a tour of the MALDI

a.i.C

ount

s

Mass

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 ….

that’s 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, that’s 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. 1.Everyone calls it AF4 = Asymmetric Flow Field Flow Fractionation2.How to you get a crossflow then? 36

Potential Advantages of FFF

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

solvents.

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30 35 4040

60

80

100

120

140

160

180

0.0

0.2

0.4

0.6

0.8

1.0

RMS radius vs Time

AF4 separation of algoflontm

LS 90o

rms

radi

us (

nm)

time (min)

rel

ativ

e in

tens

ity

AF4 can even separate large PTFElatex particles.

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Conclusion

GPC is essential in any Nano LabGPC may eventually get replaced.

Matrix FPRFFF

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