temperature. A wide range of the phase diagram is dominated by the L followed by C
phase of the PS in LC matrix. Cubic micelles were not discernable from the X-ray
results. Due to the short size of the spacer, the authors observed homogeneous
anchoring of the mesogens and only N LC phase. The strong influence of the N
phase in preventing highly curved interfaces is attributed to the absence of S
structures.
Tokita et al. (2007) reported that when the LC block is in the N phase, the BCP
cylinders and the LC director were oriented parallel to the shear direction and when
the N phase transformed into SmA, the cylindrical axis and the LC director orientation changed and they were aligned parallel to the loading direction. They attribute
this BCP structure transformation to the favorable orientation of the Sm layers
parallel to the shear plane. de Jeu et al. (Al-Hussein et al. 2005) reported the bulk
and thin film phase behavior of a polymethyl methacrylate (PMMA) and a poly
(acrylate) block copolymer having semifluorinated alkyl side chains that form Sm
LC layers. In thin films of the C forming sample ( f
LC ~ 0.65), they observed that the
Sm layers (matrix) are aligned in a favorable orientation (parallel to the substrate)
forcing the orientation of the PMMA C axis to orient perpendicular to the substrate.
However, in a typical coil-coil system, the preferred orientation of the cylindrical
long axis is parallel to the substrate. They attribute this unique C orientation to the
Sm layer formation in the system. Since the LC block is the majority, the overall
BCP morphology is dictated by the orientation of the Sm LC layers and since the
preferred orientation of the Sm layers is parallel to the substrate, the PMMA
cylinders adopt a perpendicular orientation in order to be commensurate with the
Sm layers.
Verploegan et al. (2007) also reported the strong influence of Sm LC phase in
dictating the overall BCP morphology. In a poly(styrene-b-vinyl methylsiloxane)based cylinder-forming SC-LCBCP system that forms Sm LC layers, PS C were
oriented in transverse direction and the Sm layer normal was parallel to the C axis.
The C retained their transverse orientation even when the LC was in the isotropic
phase although one would expect the cylinders to adopt their favorable orientation
(parallel to the shear direction) in such a situation. The authors conclude that the LC
layers possess residual preferential orientation even in the isotropic state. This LC
orientation influence is so strong that it prevents the C reorientation.
Osuji and co-workers recently reported macroscopic alignment of SCLCP BCP
using magnetic fields (Gopinadhan et al. 2010, 2011, 2013; Hu et al. 2014; Majewski
et al. 2010, 2013; Zhou et al. 2011). Figure 17 shows an example of the structure of a
poly(ethylene oxide-b-6-(4
0 -cyanobiphenyl-4-yloxy)-hexyl methacrylate) PEO-bPMA/CB block copolymer membrane (Majewski et al. 2010). In particular,
LiClO 4 was selectively doped into the PEO cylindrical domains for ion conduction
and the alignment of PEO cylinders was directed by the smectic poly(MA/CB) block
upon magnetic field exposure. In this work, the parallel (//) and perpendicular (⊥)
directions were defined as the PEO cylinders parallel and orthogonal to the electrode
surface, respectively. The conductivity anisotropy A reached ~ 10
3 under 5 T
magnetic field, suggesting the effective blocking of ion migration transverse to the
PEO cylinder long axis direction. Interestingly, a nearly ten-fold increase of the σ ⊥
7 Structure and Assembly of Liquid Crystalline Block Copolymers
203
phase of the PS in LC matrix. Cubic micelles were not discernable from the X-ray
results. Due to the short size of the spacer, the authors observed homogeneous
anchoring of the mesogens and only N LC phase. The strong influence of the N
phase in preventing highly curved interfaces is attributed to the absence of S
structures.
Tokita et al. (2007) reported that when the LC block is in the N phase, the BCP
cylinders and the LC director were oriented parallel to the shear direction and when
the N phase transformed into SmA, the cylindrical axis and the LC director orientation changed and they were aligned parallel to the loading direction. They attribute
this BCP structure transformation to the favorable orientation of the Sm layers
parallel to the shear plane. de Jeu et al. (Al-Hussein et al. 2005) reported the bulk
and thin film phase behavior of a polymethyl methacrylate (PMMA) and a poly
(acrylate) block copolymer having semifluorinated alkyl side chains that form Sm
LC layers. In thin films of the C forming sample ( f
LC ~ 0.65), they observed that the
Sm layers (matrix) are aligned in a favorable orientation (parallel to the substrate)
forcing the orientation of the PMMA C axis to orient perpendicular to the substrate.
However, in a typical coil-coil system, the preferred orientation of the cylindrical
long axis is parallel to the substrate. They attribute this unique C orientation to the
Sm layer formation in the system. Since the LC block is the majority, the overall
BCP morphology is dictated by the orientation of the Sm LC layers and since the
preferred orientation of the Sm layers is parallel to the substrate, the PMMA
cylinders adopt a perpendicular orientation in order to be commensurate with the
Sm layers.
Verploegan et al. (2007) also reported the strong influence of Sm LC phase in
dictating the overall BCP morphology. In a poly(styrene-b-vinyl methylsiloxane)based cylinder-forming SC-LCBCP system that forms Sm LC layers, PS C were
oriented in transverse direction and the Sm layer normal was parallel to the C axis.
The C retained their transverse orientation even when the LC was in the isotropic
phase although one would expect the cylinders to adopt their favorable orientation
(parallel to the shear direction) in such a situation. The authors conclude that the LC
layers possess residual preferential orientation even in the isotropic state. This LC
orientation influence is so strong that it prevents the C reorientation.
Osuji and co-workers recently reported macroscopic alignment of SCLCP BCP
using magnetic fields (Gopinadhan et al. 2010, 2011, 2013; Hu et al. 2014; Majewski
et al. 2010, 2013; Zhou et al. 2011). Figure 17 shows an example of the structure of a
poly(ethylene oxide-b-6-(4
0 -cyanobiphenyl-4-yloxy)-hexyl methacrylate) PEO-bPMA/CB block copolymer membrane (Majewski et al. 2010). In particular,
LiClO 4 was selectively doped into the PEO cylindrical domains for ion conduction
and the alignment of PEO cylinders was directed by the smectic poly(MA/CB) block
upon magnetic field exposure. In this work, the parallel (//) and perpendicular (⊥)
directions were defined as the PEO cylinders parallel and orthogonal to the electrode
surface, respectively. The conductivity anisotropy A reached ~ 10
3 under 5 T
magnetic field, suggesting the effective blocking of ion migration transverse to the
PEO cylinder long axis direction. Interestingly, a nearly ten-fold increase of the σ ⊥
7 Structure and Assembly of Liquid Crystalline Block Copolymers
203