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Polymer Fiber Morphology and Mechanical Properties in Liquid Crystal Polymers

Explore the hierarchical structure of liquid crystal polymers, from skin to core, macrofibrils to microfibrils, and folded chain crystals. Learn about the mechanical properties and morphology transitions of these polymers, including crystalline and amorphous regions. Discover the role of mesogens and the mesophase in determining long-range order in liquid crystal polymers.

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Polymer Fiber Morphology and Mechanical Properties in Liquid Crystal Polymers

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  1. Polymer Parameters • Chemical structure • Chemical composition and distribution • Sequence length and distribution • Molecular weight and distribution • Chain isomerism • Morphology • Topology • Additives • Cost

  2. Hierarchical Fiber Morphology “skin” “core” macrofibril (~1 µm diameter) microfibril (50 nm)

  3. Folded Chain Crystal Habit polymer melt crystallization

  4. Polytehylene

  5. Polyethylene

  6. Fiber Drawing semicrystalline lamellae microfibril

  7. Mechanical Properties microfibril amorphous 6 GPa 320 GPa crystalline

  8. Mesogens (liquid crystals)

  9. Crystal & Isotropic Liquid Long-range order - orientational - translational

  10. Polyphenyls

  11. Crystal  Mesophase  Isotropic

  12. Nematic LC Long-range order - orientational

  13. Polyphenyls

  14. NversusSA

  15. N, SA, SC

  16. Typical Calamitic Mesogen n = 6

  17. Mesogens

  18. Calamitic vs. Discotic Nematics

  19. Polymer Liquid Crystals

  20. PLCs Thermodynamics

  21. Liquid Crystalline Polymers (LCPs) • 1970’s: lyotropic LCPs (Kevlar) - ultra-high strength fibers • 1980’s: thermotropic Polyesters - stronger, low CTE, low viscosity,

  22. Ultra-high Strength Polymers react diamines with diacids Poly(p-benzamide)s 1967 Stephanie Kwolek & Paul Morgan (DuPont)

  23. “Stronger than steel?”

  24. Origin of Strength? “skin” “core” macrofibril (~1 mm diameter) extended-chain crystal habit microfibril (50 nm)

  25. I to N Transition

  26. 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.

  27. 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)

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