Bisoyi and Kumar (2008) studied the effect of inclusion of carbon nanotubes on
mesophase behavior of rufigallol-based main-chain polymers. They found that
insertion of small amount of carbon nanotubes does not affect the mesophase
structure of the pure compounds and only lowers the isotropic transition temperature. Increasing the amount of carbon nanotubes leads to decrease in isotropic
temperature. These room temperature liquid crystalline nanocomposites with broad
mesophase range and different electronic properties can be significant for many
device applications.
Discotic Main-Chain Polymers Based on Benzene
The very first benzene-based discotic main-chain liquid crystalline polymer was
prepared by Kreuder et al. (1985). These polymers were prepared via solution phase
polycondensation of difunctionalized monomers 4, 5 and 6 with various spacers
7 and 8 (Scheme 2).
Synthesis of tetraalkanoyloxy benzene polyesters 9.1–9.6 was achieved by
reacting equimolar mixture of dihyroxy tetraalkanoyloxy benzene 4 and flexible
spacer alkane-α,ω-dioic acid dichloride 7 in pyridine and toluene (Scheme 2). The
polymers 9.1 and 9.2 with short spacers were found to be non-mesomorphic
Scheme 1 Synthesis of rufigallol-based main-chain polyethers: (i) bromoalkane, NaOH, DMSO,
80
C, 24 h; (ii) α,ω-dibromoalkane, o-dichlorobenzene, aq. K 2 CO 3 , tetrabutylammonium bromide
(TBAB), 90
C, 14 days; (iii) α,ω dibromoalkane, o-dichlorobenzene, Cs 2 CO 3 , 90
C, 10 days
(redrawn from Raja et al. 1998)
Table 1 Phase behavior of discotic main-chain polyethers based on rufigallol (Ref 1: Raja et al.
1998; Ref 2: Bisoyi and Kumar 2008)
Mesogen
R
n
M w
Phase behavior
Ref
3.1
C 4 H 9
6
6800
g 72 Col r1 164 Col r2 175 I
1
3.2
C 4 H 9
8
17,000
g 72 Col h1 164 Col h2 176 I
1
3.3
C 4 H 9
10
6400
Col h1 133 Col h2 144 I
1
3.4
C 4 H 9
12
5400
Col h 138 I
1
3.5
C 8 H 17
6
7400
Col r 132 I
1
3.6
C 8 H 17
8
14,500
g 54 Col r 96 I
1
3.7
C 8 H 17
10
8800
Col r 108 I
1
3.8
C 8 H 17
12
7600
Col r 127 I
1
3.9
CH 2 CH 2 CH(CH 3 )
(CH 2 ) 3 CH(CH 3 ) 2
12
13,691
Col r 56.3 I
2
3 Liquid Crystalline Polymers Derived from Disc-Shaped Molecules
63
mesophase behavior of rufigallol-based main-chain polymers. They found that
insertion of small amount of carbon nanotubes does not affect the mesophase
structure of the pure compounds and only lowers the isotropic transition temperature. Increasing the amount of carbon nanotubes leads to decrease in isotropic
temperature. These room temperature liquid crystalline nanocomposites with broad
mesophase range and different electronic properties can be significant for many
device applications.
Discotic Main-Chain Polymers Based on Benzene
The very first benzene-based discotic main-chain liquid crystalline polymer was
prepared by Kreuder et al. (1985). These polymers were prepared via solution phase
polycondensation of difunctionalized monomers 4, 5 and 6 with various spacers
7 and 8 (Scheme 2).
Synthesis of tetraalkanoyloxy benzene polyesters 9.1–9.6 was achieved by
reacting equimolar mixture of dihyroxy tetraalkanoyloxy benzene 4 and flexible
spacer alkane-α,ω-dioic acid dichloride 7 in pyridine and toluene (Scheme 2). The
polymers 9.1 and 9.2 with short spacers were found to be non-mesomorphic
Scheme 1 Synthesis of rufigallol-based main-chain polyethers: (i) bromoalkane, NaOH, DMSO,
80
C, 24 h; (ii) α,ω-dibromoalkane, o-dichlorobenzene, aq. K 2 CO 3 , tetrabutylammonium bromide
(TBAB), 90
C, 14 days; (iii) α,ω dibromoalkane, o-dichlorobenzene, Cs 2 CO 3 , 90
C, 10 days
(redrawn from Raja et al. 1998)
Table 1 Phase behavior of discotic main-chain polyethers based on rufigallol (Ref 1: Raja et al.
1998; Ref 2: Bisoyi and Kumar 2008)
Mesogen
R
n
M w
Phase behavior
Ref
3.1
C 4 H 9
6
6800
g 72 Col r1 164 Col r2 175 I
1
3.2
C 4 H 9
8
17,000
g 72 Col h1 164 Col h2 176 I
1
3.3
C 4 H 9
10
6400
Col h1 133 Col h2 144 I
1
3.4
C 4 H 9
12
5400
Col h 138 I
1
3.5
C 8 H 17
6
7400
Col r 132 I
1
3.6
C 8 H 17
8
14,500
g 54 Col r 96 I
1
3.7
C 8 H 17
10
8800
Col r 108 I
1
3.8
C 8 H 17
12
7600
Col r 127 I
1
3.9
CH 2 CH 2 CH(CH 3 )
(CH 2 ) 3 CH(CH 3 ) 2
12
13,691
Col r 56.3 I
2
3 Liquid Crystalline Polymers Derived from Disc-Shaped Molecules
63