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Polymer Parameters

Liquid crystalline polymers (LCPs) combine the properties of solids and liquids, exhibiting unique structural characteristics such as nematic and smectic phases. This overview explores their chemical composition, molecular weight distribution, morphology, and mechanical properties, highlighting developments in thermotropic and lyotropic LCPs, including high-strength materials like Kevlar. Key advancements from the 1970s and 1980s are presented, underlining the importance of cost-effective monomers and their potential applications. References include comprehensive literature on the physical properties and processing of LCPs.

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Polymer Parameters

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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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