Keywords
Columnar · Mesophase · Liquid crystal · Column · Discotic · Entropy · Selfcompacting · Rigidified · Rigid-rod · π-stack · Side-chain · Main-chain ·
Minidendron · Cross-linked
Definition
Columnar phase-forming polymers are those polymers can organize into a
columnar mesophase where “columns” arrange in a two-dimensional longrange order while only short-range positional order exisits along the column
direction.
Introduction
Columnar phases usually refer to those mesophases or liquid crystalline (LC) phases
having lateral two-dimensional (2D) long-range ordered organization of columns
and short-range positional order along the column axis direction. The X-ray diffraction pattern of such a phase features usually resolution-limited diffractions from the
long-range ordered packing of columns, while all other diffractions are diffuse.
When polymers are in a columnar mesophase, they share some common properties
of a mesophase such as self-healing, self-organization, and the ability to respond to
external stimuli.
Although columnar phases were observed as early as the 1950s by means of
X-ray diffraction in micellar systems (Luzzati et al. 1957) and gels of
deoxyribonucleic acid and nucleoproteins (Luzzati and Nicolaieff 1959), much
of the recent interest stems from the observation of the disk-shaped molecules
(discotics) forming columnar phases (Chandrasekhar et al. 1977; Destrade et al.
1979) and the promising electronic/optoelectronic applications of such materials
(Adam et al. 1994; van de Craats et al. 1999). In a sense, “discotic” has been
considered as nearly a synonym of “columnar.” However, discotics are neither
necessary nor sufficient for a columnar phase to form. Since a columnar mesophase is a “two-dimensional array of liquid tubes” (de Gennes and Prost 1995),
the key structural elements in all columnar phases are straight columns without
long-range intracolumn positional order. Depending on the column constituent,
most columnar phase-forming polymers fall in two types. In the first type of
polymers, a column consists of a whole cylindrical polymer chain. In contrast,
columns arise as a result of self-assembly of subunits (mainly mesogens) in the
second type of polymers. In this contribution, molecular features that are essential to the appearance of a columnar mesophase in these two types of polymers are
analyzed, along with the corresponding phase structure (Chart 1).
118
S. Jin
Columnar · Mesophase · Liquid crystal · Column · Discotic · Entropy · Selfcompacting · Rigidified · Rigid-rod · π-stack · Side-chain · Main-chain ·
Minidendron · Cross-linked
Definition
Columnar phase-forming polymers are those polymers can organize into a
columnar mesophase where “columns” arrange in a two-dimensional longrange order while only short-range positional order exisits along the column
direction.
Introduction
Columnar phases usually refer to those mesophases or liquid crystalline (LC) phases
having lateral two-dimensional (2D) long-range ordered organization of columns
and short-range positional order along the column axis direction. The X-ray diffraction pattern of such a phase features usually resolution-limited diffractions from the
long-range ordered packing of columns, while all other diffractions are diffuse.
When polymers are in a columnar mesophase, they share some common properties
of a mesophase such as self-healing, self-organization, and the ability to respond to
external stimuli.
Although columnar phases were observed as early as the 1950s by means of
X-ray diffraction in micellar systems (Luzzati et al. 1957) and gels of
deoxyribonucleic acid and nucleoproteins (Luzzati and Nicolaieff 1959), much
of the recent interest stems from the observation of the disk-shaped molecules
(discotics) forming columnar phases (Chandrasekhar et al. 1977; Destrade et al.
1979) and the promising electronic/optoelectronic applications of such materials
(Adam et al. 1994; van de Craats et al. 1999). In a sense, “discotic” has been
considered as nearly a synonym of “columnar.” However, discotics are neither
necessary nor sufficient for a columnar phase to form. Since a columnar mesophase is a “two-dimensional array of liquid tubes” (de Gennes and Prost 1995),
the key structural elements in all columnar phases are straight columns without
long-range intracolumn positional order. Depending on the column constituent,
most columnar phase-forming polymers fall in two types. In the first type of
polymers, a column consists of a whole cylindrical polymer chain. In contrast,
columns arise as a result of self-assembly of subunits (mainly mesogens) in the
second type of polymers. In this contribution, molecular features that are essential to the appearance of a columnar mesophase in these two types of polymers are
analyzed, along with the corresponding phase structure (Chart 1).
118
S. Jin