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Molecular structure of calamitic LCs

Molecular structure of calamitic LCs. bridging groups. terminal groups. rigid ring systems. terminal groups. (+linking groups). (+linking groups). phenyl. carbonates. pyrimidinyl. esters. cyclohexyl. ketones. vinyl (stilbenes). thiophene. azomethine, imine (Schiff’s Base). cubane.

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Molecular structure of calamitic LCs

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  1. Molecular structure of calamitic LCs bridging groups terminal groups rigid ring systems terminal groups (+linking groups) (+linking groups) phenyl carbonates pyrimidinyl esters cyclohexyl ketones vinyl (stilbenes) thiophene azomethine, imine(Schiff’s Base) cubane azo acetylene (tolanes) biphenyl

  2. Structure and Properties p-hexaphenyl; Cr 435 S 465 N 565 I Longer chains lower the meltingpoint and promote smecticmesomorphism 4,4’-bis-(n-octyl)-p-terphenylCr 176 S 191 I n = 1: Cr 109 N (45) In = 5: Cr 24 N 35 I n = 8: Cr 21 SmA 33 N 40 n = 10: Cr 44 SmA 50 I 4-n-propyl-4’-n-heptanoyloxy-azobenzeneCr 42 N 71 I 4-n-heptyl-N-(4-n-pentyloxy-benzylidene)-anilineCr 29.5 CrG 33.9 SmB 51.0 SmC 53.1 SmA 62.8 N 78 I

  3. The Odd-Even Effect Terminal side-chains with odd carbon atoms generate higher clearing points thaneven numbered chains of comparable length. The carbon that makes the chaineven generates a deviation from the linear structure of the more favourableall-trans conformation of the chain. Both, melting and clearing temperatures arelowered due to this “disturbance”. n = 3: Cr 66 (N 25) In = 4: Cr 48 (N 16) I Branched Side-Chains Cr 4 (SmA -50 N -30) I

  4. Phasmids and Polycatenar Mesogens R2 = R5 = C12H25: Cr 110 SmC 277 N >300 I;R1 = R2 = R5 = C12H25: Cr 126 SmC 211 I;R1 = R3 = R5 = C12H25: Cr 120 Col 125 N I; Tetracatenars Hexacatenars N for short R (<C4)Col for long R (>C12) SmC in-between Col Cub

  5. Chain-Number Mediated Mesomorphism of Polycatenars Dicatenar Tetracatenar Hexacatenar SmA SmC Col Each molecular layer of the columnar stackscontains an assembly of 3-4 hexacatenars

  6. Synthesis of Intermediates

  7. Synthesis of Polycatenars

  8. Phase Diagram of Dicyanotetracatenars

  9. New Columnar Mesophase Structure withPolar Bent-Rod Polycatenars 154º bent angle Colh 6.3 D local dipole (AM1) 0.7-0.75 nm 0.7-0.8 nm

  10. New type of anti-parallel columnar packing of polar bent-rod hexacatenar

  11. Antiparallel Dipole-Dipole Nearest Neighbor Correlation Nematic liquid crystallinemodel compound Single Crystal Structure:Space Group P21

  12. Nearest Neighbor Interactions Dictated byShape and Dipolar Anisotropy polar arrangement non-polar arrangement • ferro- and anti-ferroelectricmaterials • flexoelectric materials • NLO active materials • biaxial N and SmA mesophases

  13. Mesomorphism of Bent-Rod Catenars with Strong Lateral Dipole S. Holger Eichhorn, Alexander Paraskos, Keiki Kishikawa, Timothy M. Swager Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue,Cambridge, Massachusetts 02139, USA Nematic Columnar Smectic C

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