2,5-norbornadiene), as a 1,2-insertion catalyst because the Rh complex catalyst
would not be poisoned by the polar ester group. For the two polyacetylenes obtained,
only the polymer with a medium length of alkyl tails shows an SmA phase, while the
other one with a methyl end group is not liquid crystalline. With the same method
using WCl 6 -Ph 4 Sn catalysts, they also synthesized mesogen-jacketed polyacetylenes
containing a terphenyl side-chain core (Peng et al. 2010). A short spacer was
introduced to facilitate polymerization. The polymers show enantiotropic SmA
phases. Owing to stronger “jacketing” effect of the terphenyl mesogens, the more
extended and planar conformation with a better conjugation for the disubstituted
polyacetylene leads to the better photoluminescence compared with the monosubstituted polyacetylene.
Recently, Yu et al. successfully synthesized polyacetylene MJLCPs containing a
Tp unit and a short spacer in the side chain, as shown in Chart 5, using [Rh(NBD)Cl] 2
as the catalyst (Yu et al. 2013). Unlike the mesogen-jacketed polyacetylenes synthesized by Chen et al., these polymers possess a columnar shape and form Col h phases
owing to the introduction of the Tp unit.
Polymer Reaction
MJLCPs can also be prepared from polymeric precursors through polymer reaction.
Polymethylhydrosiloxane can undergo hydrosilylation with the addition of vinyl
compounds such as styrenic derivatives. Such a reaction has been employed in the
synthesis of conventional SCLCPs. MJLCPs with a short spacer were obtained with
this method, as shown in Scheme 11 (Zhang et al. 2010). Although the polysiloxane
OOC
COO
OR
RO
OOC
COO
OR
RO
R = -CH3, -C6H13
[Rh(NBD)Cl]2
Toluene
x
Scheme 10 Synthesis of polyacetylene-based MJLCPs (Chen et al. 2006a)
n = 1, 3
OC 6 H 13
C 6 H 13 O
C 6 H 13 O
OC 6 H 13
OC 6 H 13
(CH 2 ) n
O
x
Chart 5 Chemical structure
of polyacetylene-based
MJLCP with triphenylene in
the side chain
2 Mesogen-Jacketed Liquid Crystalline Polymers: Molecular Design and. . .
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