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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


  1. How do giant molecules wiggle? Ashish Lele National Chemical Laboratory Acknowledgement: Chirag, Omkar, NCL Academy

  2. Contents � Giant molecules and their applications � Unusual flow behaviour � Solids, liquids and…. � Wiggling motions

  3. Giant molecules H H H H Polymers OR n C C C C Macromolecules n H H X X

  4. Giant molecules Molecular size ( Å) Molecule Molecular weight (g/mol) H 2 2 1.5 O 2 32 3.0 CO 2 44 3.3 Ethylene 28 1.7 Benzene 78 2.8 Fullerene C 60 720 10 Polyethylene 50,000 – 5,000,000 100 Silk 400,000 100 DNA >10 6 7300

  5. Long chains? � Proposed the concept of polymers in 1920. � Colloidal chemists rejected the idea. Hermann Staudinger 1881-1965 Awarded Nobel Prize in Chemistry in 1953. � � Rightfully called the father of polymer chemistry.

  6. Can we live without them ?

  7. 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)

  8. How are they shaped? heating flowing Plastics Melt Shaping

  9. How are they shaped?

  10. How are they shaped?

  11. How are they shaped?

  12. Flow behaviour demos… � Rod climbing � Extrudate swell � Melt fracture � Filament stretching � Dilatency and yield stress

  13. Is this solid or liquid?

  14. Solids (Elastic) � Recovery (memory) � Energy storage = − F k x � Hooke’s law Robert Hooke 1635-1703 Homework: Can you render water elastic?

  15. Molecular origin of elasticity Bond stretching Bond rotation Enthalpic Entropic

  16. Molecular origin of elasticity 0.4 probability distribution R 0.3 N steps 3 k T 0.2 = b B F R 2 Nb 0.1 0 0 2 4 6 8 10 R

  17. Liquids (Viscous) � Zero recovery (no memory) � Energy dissipation dv = − η F A � Newton’s law dy Sir Isaac Newton 1642-1727

  18. Viscoelasticity James Clerk Maxwell 1831-1879 � Fading memory � Short time elastic, long time viscous λ = � “Mountains flow before the Lord” De t p

  19. Wiggling in solutions Robert Brown 1773-1858

  20. Wiggling in solutions Rouse, P.E. Jr., 1953 ζ 2 b λ ≈ 2 N k T B Plucked string of a guitar

  21. Wiggling in melts Pierre de Gennes 1932-2007 2 k T L = λ = 3 B D ~ N ζ c N D bead c

  22. 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.

  23. THANK YOU!

  24. Rod climbing

  25. Extrudate swell

  26. Melt fracture

  27. Filament stretching

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