Macromolecules, Vol. 37, No. 1, 2004
Polymers with Banana-Shaped Mesogens 77
Ta ble 3. X-r a y Resu lts for P olym er s a n d th e Str u ctu r e of
th e Mesop h a se
and 4.00 nm, respectively indicating layer structure.
The second reflections (d2) for them were found to be
1.82 and 1.85 nm, respectively, corresponding to the
intermolecular distance including four mesogens. The
structure of the mesophase is proposed to be a two-
dimensional rectangular structure, where exists some
regularity perpendicular to normal layer. This me-
sophase has been designated as a B1 phase. As already
reported, the compounds with m/X/Y ) 12/H/H9 and
7/mono-Cl/H12 formed a B1 phase, but the compound
with 12/Cl/H12 only formed a SmC phase. Note that in
the case of our polymers m/X/Y ) 12/Cl/F or 12/Cl/Cl.
polymer
Miller plane
d spacing (nm)
d ) 3.67
3g
(001)
(002)
(001)
(002)
(003)
(001)
(100)
(001)
(100)
3h
d ) 4.65
3j
d1 ) 3.79
d2 ) 1.82
d1 ) 4.00
d2 ) 1.85
3k
presented. In Figures 5-7, at room temperature, all of
the polymers display crystalline XRD patterns, indicat-
ing a lamellar structure. When these polymers were
heated to 220, 185, and 160 °C, respectively (above the
transition temperatures of 200, 166, and 138 °C by DSC,
in that order), in the small angle region, polymer 3g
has two peaks at q ) 1.71 and 3.36 nm-1 (Figure 5b),
polymer 3h has three peaks at q ) 1.35, 2.79, and 4.18
nm-1 (Figure 6b), and polymer 3k has two peaks at q
) 1.59 and 3.48 nm-1 (Figure 7b), while their entire
wide angle regions exhibit only diffuse scattering. This
is indicative of the smectic layer structure. When the
polymers 3g and 3h were heated to 280 and 240 °C,
respectively (above the transition temperatures of 248
and 231 °C by DSC, in that order), all reflections in the
small angle region disappeared. By cooling isotropic
melts, these two polymers retained the smectic layer
structure as shown in Figures 5d and 6d. Note that only
polymer 3h could crystallize when cooled further (see
Figure 6e). In the case of polymers 3j and 3k , cooling
experiments could not be achieved due to thermal
decomposition at the temperature of the isotropic state.
In Table 3, Miller planes and d spacings for meso-
phases of the four polymers (3g, 3h , 3j, and 3k ) are
summarized. In the small angle region, polymer 3g
shows two reflections in the ratio 1:2, which are indexed
as (001) and (002). The layer spacing (d) was measured
to be 3.67 nm, indicating tilt of the molecules. As the
length of repeating unit was measured as 4.6 nm by
assuming the polymethylene chain to be fully extended
in the all-trans-conformation, the tilt of the molecules
was estimated to be about 40°. Similarly, Watanabe et
al.9 reported that B2 phase of the compound with m/X/Y
) 7/H/H only gave two reflections indexed as (001) and
(002) with a missing (003) plane. Although the XRD
patterns of the mesophase formed by polymer 3g can
be compared with those of model compounds already
reported, the existence of the B2 phase could not be
directly proven, because the melt viscosity of the
polymer is too high to investigate its switching proper-
ties. Furthermore, Pelzl et al.37 reported that the
compound with m/Y ) 8/H and one Cl atom in the
central core (X ) mono-Cl) had three equally spaced
reflections (three orders) indexed as (001), (002), and
(003), whereas we11 reported that the compound with
m/X/Y ) 8/H/F showed three reflections in the small
angle region with an integral spacing ratio. In Table 3,
polymer 3h shows three reflections in the ratio 1:2:3,
which are indexed as (001), (002), and (003). Neverthe-
less, we could not have presumed that polymer 3h gives
a B2 phase without the tilt of the molecules. This
mesophase has been identified merely as a smectic A
phase with d ) 4.65 nm. In the Table 3, in the small
angle region, polymers 3j and 3k show two reflections
which are indexed as (001) and (100). The first reflec-
tions (d1) for the two polymers were measured to be 3.79
Con clu sion
The following conclusions can be drawn from the
present work.
1. Twelve new azomethine polymers containing ba-
nana-shaped mesogenic unit have been synthesized and
characterized. The molecular structures were identified
by FT/IR and NMR spectroscopy, and the results were
in accordance with the expected molecular formula.
2. All of the polymers were soluble only in strong acid
such as H2SO4 or CF3CO2H, etc. The inherent viscosities
were in the range of 0.37-0.79 dL/g.
3. All of the polymers were semicrystalline. The
values of Tm were in the range 120-224 °C.
4. Four polymers with m ) 6 (3b, 3d , 3e, and 3f)
produced a nematic phase on heating, while two poly-
mers with m ) 6 (3a and 3c) as well as two polymers
with m ) 12 (3i and 3l) were not thermotropic liquid
crystals.
5. Of the polymers with m ) 12, the mesophase of
polymer 3g has been designated to be a B2 phase, that
of polymer 3h has been identified as a SmA phase, and
those of polymers 3j and 3k have been designated as a
B1 phase.
Ack n ow led gm en t. This work was supported by
Grant No. R01-2001-000-00433-0 from the Basic Re-
search Program of the Korea Science & Engineering
Foundation. The X-ray measurements were performed
at Pohang Accelerator Laboratory. E-J .C. thanks Pro-
fessor Edward T. Samulski at the University of North
Carolina at Chapel Hill for the discussion about deter-
mination of B-phases.
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