A main-chain nonracemic chiral liquid crystalline (LC) polyester was synthesized using
an A-Btype condensation reaction of a chiral monomer,
R-(-)4'-{
-[2-(
p-hydroxy-
o-nitrophenyloxy)-1-propyloxy]-1-heptyloxy}-4-biphenylcarboxylic acid,
and was abbreviated as PET(R*-7). Wide-
angle X-ray diffraction (WAXD)experiments combined with differential sc
anning calorimetry measurements revealed multiple phase tr
ansitionsincluding a chiral twist grain boundary A (TGBA*) phase, a chiral smectic A (SmA*) phase, a chiral smectic C(SmC*) phase,
and a highly ordered monoclinic crystalline (
KM) phase with decreasing temperature. Flat-elongated
and right-h
anded double-twisted helical single crystals were grown thermotropically in the smectic LC states.Both crystal types possessed the identical monoclinic unit cell:
a = 1.04 nm,
b = 0.46 nm,
c = 5.59 nm,
=
= 90
,
and
= 84.2
based on the WAXD
and selected area electron diffraction results. Uniaxial elongationof centimeter-sized films (along the
xz-pl
ane in a three-dimensional, 3D, coordinate system) of submillimeterthickness (along the
y-axis) resulted in macroscopic smectic monodomains. Analysis of the detailed 2D WAXDresults indicated that in the SmA* phase the molecules are parallel to the layer normal in the direction of elongation.However, in the SmC* phase, the 3D macroscopic monodomain was constructed with the layers which possessa 13
synclinically tilted layer normal with respect to the elongation direction (the
z-axis). The molecules in the3D monodomains of SmC* phase were tilted ~8
synclinically with respect to the elongation direction withinthe "in-pl
ane" of the film (within the
xz-pl
ane), tr
anslating to a ~21
tilt with respect to the layer normal. Duringthe crystallization of the K
M phase in the SmA* phase, the
c-axis of the K
M crystal is along the elongationdirection (the
z-axis), yet the
d-spacing of the (00
l) (
l = even number) pl
anes were slightly larger th
an the layerspacing of the SmA* phase. When the crystallization occurred in the 3D monodomain of the SmC* phase, on theother h
and, the synclinically tilted LC layers
and the tilted layer normal orientation with respect to the elongationdirection (the
z-axis) were retained in the K
M crystal, although the
d-spacing of the (00
l) (
l = even number)pl
anes was larger th
an the layer spacing of the SmC* phase. The most striking observation was that in order toform the K
M crystals in the SmC* phase the molecules must undergo a remarkable reorientation (~21
tilting)to became a single-crystal-like monodomain while retaining the synclinically tilted layer structure.
