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Polymer Parameters. Chemical structure Chemical composition and distribution Sequence length and distribution Molecular weight and distribution Chain isomerism Morphology Topology Additives Cost. Hierarchical Fiber Morphology. “skin”. “core”. macrofibril (~1 µ m diameter).

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Polymer parameters l.jpg
Polymer Parameters

  • Chemical structure

    • Chemical composition and distribution

    • Sequence length and distribution

  • Molecular weight and distribution

  • Chain isomerism

  • Morphology

  • Topology

  • Additives

  • Cost


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Hierarchical Fiber Morphology

“skin”

“core”

macrofibril (~1 µm diameter)

microfibril (50 nm)


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Folded Chain Crystal Habit

polymer melt

crystallization




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Fiber Drawing

semicrystalline

lamellae

microfibril


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Mechanical Properties

microfibril

amorphous

6 GPa

320 GPa

crystalline



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Crystal & Isotropic Liquid

Long-range order

- orientational

- translational



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Crystal  Mesophase  Isotropic


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Nematic LC

Long-range order

- orientational



N versus s a l.jpg
NversusSA


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N, SA, SC




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Calamitic vs. Discotic Nematics




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Liquid Crystalline Polymers (LCPs)

  • 1970’s: lyotropic LCPs (Kevlar)

    - ultra-high strength fibers

  • 1980’s: thermotropic Polyesters

    - stronger, low CTE, low viscosity,


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Ultra-high Strength Polymers

react diamines with diacids

Poly(p-benzamide)s

1967 Stephanie Kwolek & Paul Morgan (DuPont)



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Origin of Strength?

“skin”

“core”

macrofibril (~1 mm diameter)

extended-chain

crystal habit

microfibril (50 nm)


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I to N Transition


Liquid crystalline polymers lcps26 l.jpg
Liquid Crystalline Polymers (LCPs)

  • 1970’s: lyotropic LCPs (Kevlar)

    - ultra-high strength fibers

  • 1980’s: thermotropic Polyesters

    - stronger, low CTE, low viscosity,

Key: Inexpensive monomers.


Liquid crystalline polymers lcps27 l.jpg
Liquid Crystalline Polymers (LCPs)

  • Some introductory literature

  • E. T. Samulski “The Mesomorphic State”, Chapter 5 in Physical Properties of Polymers, 3rd Edt, Cambridge University Press (2004)

  • D. Acierno and A. A. Collyer, Rheology and Processing of Liquid Crystal Polymers, Chapman & Hall (1996)

  • N. A. Plate, Editor. Liquid Crystalline Polymers, Plenum Press, NY (1993).

  • A. A. Collyer, Edt. Liquid Crystal Polymers: From Structures to Applications, Elsevier Applied Science Publishers, London (1992).

  • A. M. Donald and A. H. Windle, Liquid Crystalline Polymers, Cambridge University Press (1991)