(Table 2). However, the polymers with long spacers 9.3, 9.4 and 9.5 were found to be
liquid crystalline. The liquid crystalline nature disappeared when spacer length in
polymer 9.6 was increased to 20 methylene units (Kreuder et al. 1985).
Replacing the flexible spacer, alkane-α,ω-dioic acid dichloride 7 with
terephthaloyl dichloride 8 gave the benzoate-based polyesters. Thermal analysis of
polyesters 10.1–10.4 showed that the polyesters 10.1, 10.2 and 10.3 with four lateral
alkyl chains were liquid crystalline (Table 3). However, polyester 10.4 having six
lateral chains did not exhibit any mesomorphism. The isotropization temperature of
these polymers depends on the lateral alkyl chain length of difunctionalized benzene
monomers. The synthesis of corresponding tetraalkoxy benzene-derived polybenzoates is shown in Schemes 3 and 4 (Schönherr et al. 1986; Ringsdorf et al.
1987). It was noticed that polymers with four lateral alkyl chains 11.1 and 11.2 were
liquid crystalline, whereas polymers with six lateral alkyl chains 11.3 and 11.4 were
found to be non-mesomorphic.
Scheme 2 Synthesis of tetraalkanoyloxy benzene polyesters: (i) pyridine, toluene, R.T., 5 days;
(ii) pyridine, toluene, À20
C, 2 h, R.T., 5 days (redrawn from Kreuder et al. 1985 and Schönherr
et al. 1986)
Table 2 Phase behavior of tetraalkanoyloxy benzene polyesters (Ref 3: Kreuder et al. 1985)
Mesogen
n
Mn
Phase behavior
Ref
9.1
7
–
g 54 I
3
9.2
8
10,400
g 55 I
3
9.3
10
9800
g 55 M 95 I
3
9.4
12
12,400
g 54 M 97 I
3
9.5
14
12,100
Cr 64 M 92 I
3
9.6
20
6600
g 30 I
3
64
S. Setia et al.