cooled from the LC phase. The similar behavior in PBPCS was confirmed by
experimental results such as those of differential scanning calorimetry (DSC) and
PLM, as shown in Fig. 6 (Chen et al. 2010; Zhao et al. 2006). The unusual transition
from the isotropic liquid to the LC phase during heating is entropy driven, which can
be rationalized by the higher entropy gain owing to the increased freedom of side
chains when the MJLCP is in the LC state compared to the entropy loss of the main
chain in the ordered LC phase.
Chirality Transfer
MJLCPs have interesting behaviors in chirality transfer. As shown in Scheme 1, the
MJLCP PMBPS with chiral groups attached at the ends of the side-chain mesogen
has a helical secondary structure formed during the free radical polymerization
(Yu et al. 2003b). The helical conformation is maintained even when the chiral
groups are chemically removed from the side chain.
During the free radical polymerization of bulky vinyl monomers containing
laterally attached p-terphenyl groups and a single asymmetric center, the stereogenic
centers in the side chains of the monomers can transfer the chirality to the propagating polymer chains (Cui et al. 2009). In addition, optically active helical
mesogen-jacketed copolymers obtained from the radical copolymerization of a chiral
monomer and an achiral monomer display an unusual linear optical activitycomposition relationship, in sharp contrast to the “sergeants-and-soldiers” and
“majority” rules (Cui et al. 2010).
Fig. 6 Unusual phase behavior of PBPCS (polymer 5 with n = 4). (a) DSC thermograms show
enantiotropic transitions which have small but non-negligible latent heat. PLM results (inset
micrographs) show that the sample is birefringent at high temperatures, indicating the existence
of a mesophase, while the sample is isotropic at low temperatures. (b) The wormlike chain changes
to a rodlike chain during heating, which is driven by entropy, and this transformation is reversible
upon cooling. The rods self-organized into a Col hn phase which has weak lateral hexagonal order.
(Reprinted and adapted with permission of the American Chemical Society (Zhao et al. 2006) and
the Royal Society of Chemistry (Chen et al. 2010))
2 Mesogen-Jacketed Liquid Crystalline Polymers: Molecular Design and. . .
37
experimental results such as those of differential scanning calorimetry (DSC) and
PLM, as shown in Fig. 6 (Chen et al. 2010; Zhao et al. 2006). The unusual transition
from the isotropic liquid to the LC phase during heating is entropy driven, which can
be rationalized by the higher entropy gain owing to the increased freedom of side
chains when the MJLCP is in the LC state compared to the entropy loss of the main
chain in the ordered LC phase.
Chirality Transfer
MJLCPs have interesting behaviors in chirality transfer. As shown in Scheme 1, the
MJLCP PMBPS with chiral groups attached at the ends of the side-chain mesogen
has a helical secondary structure formed during the free radical polymerization
(Yu et al. 2003b). The helical conformation is maintained even when the chiral
groups are chemically removed from the side chain.
During the free radical polymerization of bulky vinyl monomers containing
laterally attached p-terphenyl groups and a single asymmetric center, the stereogenic
centers in the side chains of the monomers can transfer the chirality to the propagating polymer chains (Cui et al. 2009). In addition, optically active helical
mesogen-jacketed copolymers obtained from the radical copolymerization of a chiral
monomer and an achiral monomer display an unusual linear optical activitycomposition relationship, in sharp contrast to the “sergeants-and-soldiers” and
“majority” rules (Cui et al. 2010).
Fig. 6 Unusual phase behavior of PBPCS (polymer 5 with n = 4). (a) DSC thermograms show
enantiotropic transitions which have small but non-negligible latent heat. PLM results (inset
micrographs) show that the sample is birefringent at high temperatures, indicating the existence
of a mesophase, while the sample is isotropic at low temperatures. (b) The wormlike chain changes
to a rodlike chain during heating, which is driven by entropy, and this transformation is reversible
upon cooling. The rods self-organized into a Col hn phase which has weak lateral hexagonal order.
(Reprinted and adapted with permission of the American Chemical Society (Zhao et al. 2006) and
the Royal Society of Chemistry (Chen et al. 2010))
2 Mesogen-Jacketed Liquid Crystalline Polymers: Molecular Design and. . .
37