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How do giant molecules wiggle?
Ashish Lele National Chemical Laboratory
Acknowledgement: Chirag, Omkar, NCL Academy
Contents
Giant molecules and their applications Unusual flow behaviour Solids, liquids and…. Wiggling motions
How do giant molecules wiggle? Ashish Lele National Chemical - - PowerPoint PPT Presentation
How do giant molecules wiggle? Ashish Lele National Chemical - - PowerPoint PPT Presentation
How do giant molecules wiggle? Ashish Lele National Chemical Laboratory Acknowledgement: Chirag, Omkar, NCL Academy Contents Giant molecules and their applications Unusual flow behaviour Solids, liquids and. Wiggling motions
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Giant molecules
C C H H H X C C H H H X
n n
Polymers OR Macromolecules
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Giant molecules
7300 >106 DNA 100 400,000 Silk 100 50,000 – 5,000,000 Polyethylene 10 720 Fullerene C60 2.8 78 Benzene 1.7 28 Ethylene 3.3 44 CO2 3.0 32 O2 1.5 2 H2
Molecular size (Å) Molecular weight (g/mol) Molecule
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Long chains?
Hermann Staudinger 1881-1965
Proposed the concept of polymers in 1920. Colloidal chemists rejected the idea.
- Awarded Nobel Prize in Chemistry in 1953.
Rightfully called the father of polymer chemistry.
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Can we live without them ?
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Why are they so popular?
Excellent properties Easy to shape into products Cheap Reusable Good service life …..
We consumed 7 million tons in 2008 !! (Mutha et al, 2006)
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How are they shaped?
Plastics Melt Shaping
heating flowing
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How are they shaped?
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How are they shaped?
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How are they shaped?
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Flow behaviour demos…
Rod climbing Extrudate swell Melt fracture Filament stretching Dilatency and yield stress
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Is this solid or liquid?
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Solids (Elastic)
x k F − =
Recovery (memory) Energy storage Hooke’s law
Homework: Can you render water elastic?
Robert Hooke 1635-1703
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Molecular origin of elasticity
Bond stretching Enthalpic Bond rotation Entropic
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Molecular origin of elasticity
R Nb T k F
B 2
3 =
0.1 0.2 0.3 0.4 2 4 6 8 10
R
probability distribution
N steps b R
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Liquids (Viscous)
Zero recovery (no memory) Energy dissipation Newton’s law
dy dv A F η − =
Sir Isaac Newton 1642-1727
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Viscoelasticity
Fading memory Short time elastic, long time viscous “Mountains flow before the Lord”
p
t De λ =
James Clerk Maxwell 1831-1879
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Wiggling in solutions
Robert Brown 1773-1858
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Wiggling in solutions
2 2
N T k b
B
ζ λ ≈
Rouse, P.E. Jr., 1953
Plucked string of a guitar
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Wiggling in melts
3 2
~ N D L N T k D
c bead B c
= = λ ζ
Pierre de Gennes 1932-2007
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Why are wiggling motions important?
Choosing the right polymer for an application. Choosing the right equipment for a polymer. Influence on solidification processes. Biological processes.
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THANK YOU!
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Rod climbing
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Extrudate swell
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Melt fracture
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