the formation of a helical superstructure in the liquid crystalline polymers
13.9–13.10 (Green et al. 1990).
In order to prepare the single isomer of difunctionalized triphenylene monomer,
Wenz (1985) rationalized the synthesis of 2,3-difunctionalized triphenylene derivative.
Polycondensation of 2,3-difunctionalized triphenylene with various α,ω-diols having
different spacer lengths gave polyester 14.1–14.5. The polycondensation of malonic
acid diethyl ester afforded polymer 15 (Vandevyver et al. 1993). In polymers 16,
triphenylene units having chiral peripheral chains were linked together via ester
linkages (Green et al. 1990). Later on Boden et al. (1995) prepared pure
2,7-dihydroxy-3,6,10,11-tetrahexyloxy-triphenylene
and
2,11-dihydroxy-3,6,7,
10-tetrahexyloxy-triphenylene. Condensation of 2,3-dihydroxy-6,7,10,11-tetrahexyloxytriphenylene with 1,10-dibromodecane gave polymer 17. The polyetherification of 2,7-dihydroxy-3,6,10,11-tetrahexyloxytriphenylene and 2,11dihydroxy-3,6,7,10-tetrahexyloxytriphenylene with α,ω-dibromoalkanes furnished
polymers 18 and 19.1 (Boden et al. 1995). Polyesterification of 2,11dihydroxytetrahexyloxytriphenylene with α,ω-diacids produced polymers 19.2–19.4
(Wan et al. 2003). Thermal studies and GPC studies of these polymers can be seen in
Table 5. The polymer 14 melt at about 93
C and clear between 100 and 200
C,
whereas polymer 15 showed the glass transition at À10
C and isotropic transition at
31
C. On doping with electron-acceptor TNF, discotic nematic phase of polymer 15
transformed into more ordered columnar phase. This charge transfer polymer composite displayed thermal transition at 135
C from columnar phase to isotropic phase
(Vandevyver et al. 1993). Polymers 16.1 and 16.2 were amorphous in nature and
Table 5 Phase behavior of main-chain polymers based on triphenylene 14–18 (Ref 10: Wenz
1985; Ref 11: Vandevyver et al. 1993; Ref 9: Green et al. 1990; Ref 12: Boden et al. 1995)
Mesogen
n
Phase behavior
Ref
14
12
g 93 Col 163 I
10
15
6
g À 10 N 31 I
11
16.1
14
g 105 I
9
16.2
20
g 75 I
9
17
10
Cr 100 Col 115 I
12
18
11
Cr 98 Col 118 I
12
Table 6 Phase behavior of main-chain polymers based on triphenylene 19 (Ref 12: Boden et al.
1995; Ref 13: Wan et al. 2003)
Mesogen
Z
n
Phase behavior
Ref
19.1
CH 2
9
Cr 93 Col 120 I
12
19.2
CO
8
g 56 Col h 211 I
13
19.3
CO
10
g 40 Col h 198 I
13
19.4
CO
12
g 25 Col h 162 I
13
3 Liquid Crystalline Polymers Derived from Disc-Shaped Molecules
67
13.9–13.10 (Green et al. 1990).
In order to prepare the single isomer of difunctionalized triphenylene monomer,
Wenz (1985) rationalized the synthesis of 2,3-difunctionalized triphenylene derivative.
Polycondensation of 2,3-difunctionalized triphenylene with various α,ω-diols having
different spacer lengths gave polyester 14.1–14.5. The polycondensation of malonic
acid diethyl ester afforded polymer 15 (Vandevyver et al. 1993). In polymers 16,
triphenylene units having chiral peripheral chains were linked together via ester
linkages (Green et al. 1990). Later on Boden et al. (1995) prepared pure
2,7-dihydroxy-3,6,10,11-tetrahexyloxy-triphenylene
and
2,11-dihydroxy-3,6,7,
10-tetrahexyloxy-triphenylene. Condensation of 2,3-dihydroxy-6,7,10,11-tetrahexyloxytriphenylene with 1,10-dibromodecane gave polymer 17. The polyetherification of 2,7-dihydroxy-3,6,10,11-tetrahexyloxytriphenylene and 2,11dihydroxy-3,6,7,10-tetrahexyloxytriphenylene with α,ω-dibromoalkanes furnished
polymers 18 and 19.1 (Boden et al. 1995). Polyesterification of 2,11dihydroxytetrahexyloxytriphenylene with α,ω-diacids produced polymers 19.2–19.4
(Wan et al. 2003). Thermal studies and GPC studies of these polymers can be seen in
Table 5. The polymer 14 melt at about 93
C and clear between 100 and 200
C,
whereas polymer 15 showed the glass transition at À10
C and isotropic transition at
31
C. On doping with electron-acceptor TNF, discotic nematic phase of polymer 15
transformed into more ordered columnar phase. This charge transfer polymer composite displayed thermal transition at 135
C from columnar phase to isotropic phase
(Vandevyver et al. 1993). Polymers 16.1 and 16.2 were amorphous in nature and
Table 5 Phase behavior of main-chain polymers based on triphenylene 14–18 (Ref 10: Wenz
1985; Ref 11: Vandevyver et al. 1993; Ref 9: Green et al. 1990; Ref 12: Boden et al. 1995)
Mesogen
n
Phase behavior
Ref
14
12
g 93 Col 163 I
10
15
6
g À 10 N 31 I
11
16.1
14
g 105 I
9
16.2
20
g 75 I
9
17
10
Cr 100 Col 115 I
12
18
11
Cr 98 Col 118 I
12
Table 6 Phase behavior of main-chain polymers based on triphenylene 19 (Ref 12: Boden et al.
1995; Ref 13: Wan et al. 2003)
Mesogen
Z
n
Phase behavior
Ref
19.1
CH 2
9
Cr 93 Col 120 I
12
19.2
CO
8
g 56 Col h 211 I
13
19.3
CO
10
g 40 Col h 198 I
13
19.4
CO
12
g 25 Col h 162 I
13
3 Liquid Crystalline Polymers Derived from Disc-Shaped Molecules
67