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

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

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

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 ( C 12 ) SmC in-between Col Cub

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

Synthesis of Intermediates

Synthesis of Polycatenars

Phase Diagram of Dicyanotetracatenars

New Columnar Mesophase Structure with Polar Bent-Rod Polycatenars nm Col h nm 154º bent angle 6.3 D local dipole (AM1)

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

Antiparallel Dipole-Dipole Nearest Neighbor Correlation Single Crystal Structure: Space Group P2 1 Nematic liquid crystalline model compound

Nearest Neighbor Interactions Dictated by Shape and Dipolar Anisotropy polar arrangementnon-polar arrangement ferro- and anti-ferroelectric materials flexoelectric materials NLO active materials biaxial N and SmA mesophases

Smectic C Columnar Nematic 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