functionalized triphenylene (TP) derivatives 44 with 10-undecenyl bromide to
produce 3,6,7,10,11-pentakis(pentyloxy)-2-(10-undecenyoxy)-triphenylene 45.
This triphenylene 45 when reacted with Si-H containing polymers gave rise to
side-chain triphenylene polymers 46 and 47 (Scheme 10). Thermal transitions of
these polymers are given in Table 10. Polymer 46 went from glassy to columnar at
À19
C and then to isotropic at 39
C on thermal annealing at 20
C for 2 days. In
another report by Werth and Spiess (1993), different thermal behavior was observed
from glassy to Col at À41
C and then to isotropic at 75
C. They have explained the
dependence of thermal behavior on polymer processing. The clearing temperature of
these polymers increased on decreasing the spacer length as shown in Table 11. The
polymers with ester linkages 49 exhibit higher clearing temperature as compared to
polymer with ether linkages 46–48 (Kreuder and Ringsdorf 1983; Hüser and Spiess
1988; Werth and Spiess 1993; Hüser et al. 1989).
Scheme 9 Synthesis of hexabenzocoronene-based side-chain ionic polymers (redrawn from
Thunemann et al. 1999, 2000, 2003)
3 Liquid Crystalline Polymers Derived from Disc-Shaped Molecules
77