and show a clear transition from mesophase to isotropic phase. Table 9 summarizes
the thermal transition data of these polymers.
Kouwer et al. (2001) also synthesized side-chain pentaalkynylbenzene-based
co-polyacrylates 39.1–39.10. The quenching in the final stage involved two steps.
First step involved the partial quenching with an alcohol other than methanol and
secondly with excess methanol. All copolymers displayed nematic columnar phase
at lower temperatures. Thermal behavior of these polymers suggested that higher
weight percentage of discotic mesogen in the copolymer increases the glass transition as well as clearing temperature and induces the formation of nematic phase at
higher temperature.
Scheme 8 Synthesis of alkynylbenzene-based side-chain polyacrylates: (i) AIBN, dioxane;
(ii) 37, C 5 H 5 N, DMAP, CH 2 Cl 2 (redrawn from Kouwer et al. 2002a, b, 2003)
Table 9 Phase behavior of alkynylbenzene-based side-chain polyacrylates (Ref 18: Kouwer et al.
2003; Ref 19: Kouwer et al. 2002a; Ref 20: Kouwer et al. 2002b)
Mesogen
R
x
Phase behavior
Ref.
38.1
C 7 H 15
0.50
g À 15 I
18
38.2
OC 6 H 13
0.60
g 25 N 107 I
18
38.3
OC 6 H 13
0.63
g 24 N 113 I
18
38.4
OCH 3
0.63
g 41 N > 200 dec
19
38.5
OCH 3
0.70
g 50 N > 200 dec
19
38.6
OCH 3
0.83
g 45 N > 200 dec
19
38.7
H
0.72
g 53 I
20
3 Liquid Crystalline Polymers Derived from Disc-Shaped Molecules
75