of the two chiral pairs, it is expected that the two structures form with equal
probability and that polymer films with alternating gyroid morphology are thus
constituted by grain mixtures of the two chiral pairs. In contrast, chiral BCPs can
discriminate between two chiral pairs due to differences in free energy between
them, leading to the formation of chiral structures. Ho et al. synthesized chiral BCPs
and obtained 3D chiral helices [32], where local interactions between chiral
components led to a chiral structure at the mesoscale.
Many of these noncubic 3D structures are believed to be metastable because
interfacial areas are usually larger than those of 1D lamellar or 2D hexagonal
structures, thus leading to higher enthalpic repulsions. Therefore, many of the
experimentally observed cases are believed to be long-lived metastable states.
3.4 Quasicrystalline Structures
A quasicrystal is a quasiperiodic structure that is ordered but aperiodic, i.e., it lacks
translational order. Its unit cell has defined angles and distances with respect to
other unit cells but long-range translational order is missing. In addition to
intriguing structural characteristics, the transport properties of quasicrystals are
expected to be unique due to the missing translational order. For example, Man
et al. showed that photonic quasicrystals are excellent candidates for photonic band
gap materials, where the existence of photonic waves is forbidden in photonic band
gap ranges [35].
There have been few reports to date on quasicrystalline structure formation
from BCPs. Hayashida et al. obtained a 2D quasicrystalline structure, a tiling
pattern with 12-fold symmetry, from an ABC star BCP and homopolymer blend
(see Fig. 3) [34]. The Bates group at the University of Minnesota generated a 3D
dodecagonal quasicrystal from diblock and tetrablock copolymers [33]. These
unique structures are mediated by macromolecular packing frustration. However,
a substantial number of unanswered questions about the structure formation await
further in-depth studies of these interesting morphologies.
BCPs offer a variety of structures including 1D, 2D, 3D, and quasicrystalline
structures. BCP SA is a useful approach for generating structures at the mesoscale,
ranging from a few to hundreds of nanometers. The structural diversity of BCP SA
provides facile access to nanostructures, but flexible polymer blocks used for structure formation usually lack useful chemical and physical properties for applications.
The Wiesner group has devoted much effort to combine BCP SA with the properties
of functional materials to exploit the power of BCPs as structure-directing agents.
The next section summarizes the synthetic strategies used by the Wiesner group for
the generation of functional nanomaterials from BCP SA with multiple levels of
structural characteristics.
Design and Applications of Multiscale Organic–Inorganic Hybrid Materials. . .
269
probability and that polymer films with alternating gyroid morphology are thus
constituted by grain mixtures of the two chiral pairs. In contrast, chiral BCPs can
discriminate between two chiral pairs due to differences in free energy between
them, leading to the formation of chiral structures. Ho et al. synthesized chiral BCPs
and obtained 3D chiral helices [32], where local interactions between chiral
components led to a chiral structure at the mesoscale.
Many of these noncubic 3D structures are believed to be metastable because
interfacial areas are usually larger than those of 1D lamellar or 2D hexagonal
structures, thus leading to higher enthalpic repulsions. Therefore, many of the
experimentally observed cases are believed to be long-lived metastable states.
3.4 Quasicrystalline Structures
A quasicrystal is a quasiperiodic structure that is ordered but aperiodic, i.e., it lacks
translational order. Its unit cell has defined angles and distances with respect to
other unit cells but long-range translational order is missing. In addition to
intriguing structural characteristics, the transport properties of quasicrystals are
expected to be unique due to the missing translational order. For example, Man
et al. showed that photonic quasicrystals are excellent candidates for photonic band
gap materials, where the existence of photonic waves is forbidden in photonic band
gap ranges [35].
There have been few reports to date on quasicrystalline structure formation
from BCPs. Hayashida et al. obtained a 2D quasicrystalline structure, a tiling
pattern with 12-fold symmetry, from an ABC star BCP and homopolymer blend
(see Fig. 3) [34]. The Bates group at the University of Minnesota generated a 3D
dodecagonal quasicrystal from diblock and tetrablock copolymers [33]. These
unique structures are mediated by macromolecular packing frustration. However,
a substantial number of unanswered questions about the structure formation await
further in-depth studies of these interesting morphologies.
BCPs offer a variety of structures including 1D, 2D, 3D, and quasicrystalline
structures. BCP SA is a useful approach for generating structures at the mesoscale,
ranging from a few to hundreds of nanometers. The structural diversity of BCP SA
provides facile access to nanostructures, but flexible polymer blocks used for structure formation usually lack useful chemical and physical properties for applications.
The Wiesner group has devoted much effort to combine BCP SA with the properties
of functional materials to exploit the power of BCPs as structure-directing agents.
The next section summarizes the synthetic strategies used by the Wiesner group for
the generation of functional nanomaterials from BCP SA with multiple levels of
structural characteristics.
Design and Applications of Multiscale Organic–Inorganic Hybrid Materials. . .
269