H
H
H
H
H
Ph
Yellow
Closed form
(Pale yellow)
Open form
(Dark purple)
Red
Ph
O
O
OR
+
O
hν
UV (>260 nm)
UV (<260 nm)
hν' or Δ
hν' or Δ
hν
hn 1
hn 2 or Δ
O
O
O
O
O
O
O
O
OR
OR
RO
trans-azobenzene
cis-azobenzene
N
N
N
N
N
NO 2
NO 2
O
N
Fig. 1 Structure of common chromophore molecules and their photoactivity
UV
Radiation off
LC phase
Isotropic Phase
Mesogen
trans- Azo
Fig. 2 Pictorial
representation of trans-cis
isomerization under
irradiation and resultant
LC-iso-transition and back
process
394
A. B. Samui
H
H
H
H
Ph
Yellow
Closed form
(Pale yellow)
Open form
(Dark purple)
Red
Ph
O
O
OR
+
O
hν
UV (>260 nm)
UV (<260 nm)
hν' or Δ
hν' or Δ
hν
hn 1
hn 2 or Δ
O
O
O
O
O
O
O
O
OR
OR
RO
trans-azobenzene
cis-azobenzene
N
N
N
N
N
NO 2
NO 2
O
N
Fig. 1 Structure of common chromophore molecules and their photoactivity
UV
Radiation off
LC phase
Isotropic Phase
Mesogen
trans- Azo
Fig. 2 Pictorial
representation of trans-cis
isomerization under
irradiation and resultant
LC-iso-transition and back
process
394
A. B. Samui