Cross-Linked Columnar LC Phase-Forming Polymers
Columnar mesophases may also form in cross-linked polymers which are typically
prepared by polymerizing a multifunctional monomer in its columnar LC phase.
All three HBC monomers shown in Chart 13 exhibit a broad Col h phase temperature range suitable for thermal polymerization. The polymerization of HBCV1
gives a very low conversion and a product mixture with DP up to 4, probably due
to the low concentration of polymerizable groups. In contrast, thermal polymerization of HBCV2A and HBCV2MA leads to corresponding cross-linked polymers
with ~60% conversion. Both cross-linked polymers exhibit a highly ordered Col h
phase in a very broad temperature range from À50 to 300
C (decomposition)
(Brand et al. 2000).
Similar to HBCs, phthalocyanines PcHA, PcHMA, and PcCuMA were successfully polymerized thermally in the Col h phase. X-ray diffraction has shown that the
resulting cross-linked polymers retain the highly ordered Col h phase with a tight
π-stack (intra-stack spacing ~ 0.33 nm) (van der Pol et al. 1990).
Besides the addition reaction of vinyl groups, azide-alkyne [3 + 2] cycloaddition
was also utilized to cross-link discotic molecules (Kayal et al. 2013). A 1:1 mixture
of CuTAPA3 and CuTAPB3 exhibits its Col h phase over À50 to 100
C. The mixture
was slowly cross-linked via thermally activated azide-alkyne [3 + 2] cycloaddition at
65
C while in its Col h phase. The X-ray diffraction results showed that the phase
structure hardly changes during the reaction which eventually leads to an insoluble
3D network polymer in its Col h phase. In contrast, the cross-linking reaction of
thesame mixture in solution, catalyzed by Cu
+
, produced an amorphous insoluble
polymer, highlighting the importance of carrying out cross-link reaction with
the monomer in its columnar LC phase.
PTP1-5-m, m =
8, 10, 12, 14, 16
PTP2-5-m, m = 8, 14, 20
PTP3
PTP4-p-m, p =5, 7; p =12, 14, 20
PolyPc1, R = C 8 H 17
Chart 12 Structures of columnar LC phase-forming polymers with mesogens in the main-chain
140
S. Jin
Columnar mesophases may also form in cross-linked polymers which are typically
prepared by polymerizing a multifunctional monomer in its columnar LC phase.
All three HBC monomers shown in Chart 13 exhibit a broad Col h phase temperature range suitable for thermal polymerization. The polymerization of HBCV1
gives a very low conversion and a product mixture with DP up to 4, probably due
to the low concentration of polymerizable groups. In contrast, thermal polymerization of HBCV2A and HBCV2MA leads to corresponding cross-linked polymers
with ~60% conversion. Both cross-linked polymers exhibit a highly ordered Col h
phase in a very broad temperature range from À50 to 300
C (decomposition)
(Brand et al. 2000).
Similar to HBCs, phthalocyanines PcHA, PcHMA, and PcCuMA were successfully polymerized thermally in the Col h phase. X-ray diffraction has shown that the
resulting cross-linked polymers retain the highly ordered Col h phase with a tight
π-stack (intra-stack spacing ~ 0.33 nm) (van der Pol et al. 1990).
Besides the addition reaction of vinyl groups, azide-alkyne [3 + 2] cycloaddition
was also utilized to cross-link discotic molecules (Kayal et al. 2013). A 1:1 mixture
of CuTAPA3 and CuTAPB3 exhibits its Col h phase over À50 to 100
C. The mixture
was slowly cross-linked via thermally activated azide-alkyne [3 + 2] cycloaddition at
65
C while in its Col h phase. The X-ray diffraction results showed that the phase
structure hardly changes during the reaction which eventually leads to an insoluble
3D network polymer in its Col h phase. In contrast, the cross-linking reaction of
thesame mixture in solution, catalyzed by Cu
+
, produced an amorphous insoluble
polymer, highlighting the importance of carrying out cross-link reaction with
the monomer in its columnar LC phase.
PTP1-5-m, m =
8, 10, 12, 14, 16
PTP2-5-m, m = 8, 14, 20
PTP3
PTP4-p-m, p =5, 7; p =12, 14, 20
PolyPc1, R = C 8 H 17
Chart 12 Structures of columnar LC phase-forming polymers with mesogens in the main-chain
140
S. Jin