Angewandte Fluororganische Chemie: Synthese ... - Fluorine

H 7 C 3
H 7 C 3
H 7 C 3
Oligo(1,3-dioxane) Concept: Results
O
O
O
O
O
O
O
O
CN
C 3 H 7
O
O
C 59 S B (53) N 82.1 I
T NI,extr = 19.3°C
Δε = 9.4 Δn = 0.061
γ 1 = 295 mPa·s
C 82 S B 125 I
T NI,extr = -0.7°C
Δε = 8.3 Δn = 0.048
γ 1 = 98 mPa·s
C 5 H 11
C 169 S B 234 I
• insufficient solubility
in ZLI-4792
Oligo(1,3-dioxane) Based Liquid Crystals
Influence of Conformation on Dielectric Anisotropy
P. KIRSCH: Angewandte fluororganische Chemie: Synthese, Pharmazeutika, Flüssigkristalle 46
Dielectric Anisotropy ( )
14
12
10
8
6
4
2
0
O
O
H
O
O
R
H
H
O
O
anti H
gauche
180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0
Torsion Angle
• Most polar non-fluorinated material so far
which is still suitable for AM-LCD
• Very low birefringence (Δn)
• Significantly improved rotational viscosity (γ 1 )
• Disadvantages are smectic B phases and poor
solubility in fluorinated LC host mixtures
• Clear demonstration of the strong influence of
the conformational equilibrium on electrooptical
properties
4.5. Brücken innerhalb des mesogenen Grundkörpers:
Phase Sequence /ºC
120
100
80
60
40
20
0
Die Difluoroxymethylenbrücke
74.7
N
C
F
F
F
F
CCP-3F.F.F (1) F
CCQU-3-F (2)
91.5
1 2
Operating Temperature
Range
CF 2 O Bridged Liquid Crystals
Physical Properties
Dielectric Anisotropy (Δε)
12
10
8
6
4
2
0
1 2
Rotational Viscosity (γ 1 ) /mPa·s
180
160
140
120
100
80
60
40
20
0
O
F
F
F
1 2
Driving Voltage Switching Time
Route A
Synthesis of CF 2 O Bridged Liquid Crystals
Prior Work on Aromatic Systems
R CHO
SF4 R CHF R 2
Br2 , hν
CF2Br PhONa
Route B
R CF 3 R CF 2 Cl
AlCl 3
S
S
DAST or NBS, Bu4NH2F3 R Br R
1. Mg
2. CSCl
Route C
2
R
Cl
PhOH,
pyridine
O
X
O
Lawesson's Reagent
Route D
R
X
O
• A. Haas, M. Spitzer, M. Lieb, Chem. Ber. 1988, 121, 1329-1340.
• E. Bartmann, Adv. Mater. 1996, 8, 570-573.
• E. Bartmann, K. Tarumi (Merck KGaA), DE 19531165, 1995.
• M. Kuroboshi, T. Hiyama, Synlett 1994, 251-252.
• T. Ando et al. (Chisso Corp.), EP 0844229, 1998.
O
O
3
2.5
2
1.5
1
0.5
0
0 ) /kcal mol -1
R
Relative Torsion Energy ( H f
R CF2O PhONa
X