either columnar or smectic, is directly correlated with the size of the side chain. While
the first MJLCPs have laterally attached mesogenic side chains, bulky side chains
that are not mesogenic can also be used to construct MJLCPs. The “jacketing” effect,
i.e., the steric hindrance caused by the densely packed side chains, forces the polymer
backbone to take an extended-chain conformation. Many factors, such as MW,
backbone flexibility, tail length, and architecture, influence the phase behaviors of
MJLCPs. With the understanding of the chemical structure-phase behavior relationships, molecular design for MJLCPs can be executed by carefully choosing molecular parameters including the shape and rigidity of the side chain, the structure of the
polymer backbone, and so on. MJLCPs can be synthesized by radical polymerizations that do not require highly pure solvents and reagents. Many controlled/living
radical polymerization methods, such as nitroxide-mediated radical polymerization
(NMRP) and atom transfer radical polymerization (ATRP), can also be employed.
Recently, another living polymerization method, ring-opening metathesis polymerization (ROMP), has been applied in the synthesis of MJLCPs with a polynorbornene
backbone. With the use of such controlled polymerization methods, the length of the
rodlike or sheetlike MJLCP chain can be tuned by adjusting the MW. In addition,
MJLCPs can also be synthesized by polymer reactions from prepolymers like poly
(methylsiloxane)s. Furthermore, MJLCPs can also be obtained by taking advantage
of supramolecular chemistry, with the application of hydrogen bonding, ionic interaction, and other non-covalent interactions. Future directions in the study of MJLCPs
will be to address the main challenges by designing monomers that can be more
easily synthesized and polymerized, establishing cost- and time-saving synthetic
methods, applying calculation and computer simulation that can accurately predict
phase behaviors and guide molecular design, and developing functional MJLCP
materials.
Keywords
Mesogen-jacketed liquid crystalline polymer · “Jacketing” effect · Liquid
crystalline phase · Columnar phase · Smectic phase · Structure-property
relationship · Free radical polymerization · Controlled/living radical
polymerization · Nitroxide-mediated radical polymerization (NMRP) · Atom
transfer radical polymerization (ATRP) · Reversible addition-fragmentation chain
transfer (RAFT) · Ring-opening metathesis polymerization (ROMP)
Definition
Mesogen-jacketed liquid crystalline polymers (MJLCPs) are side-chain polymers
that have significant chain rigidity and form liquid crystalline (LC) phases. The first
MJLCPs have laterally attached mesogenic side chains that are connected to the
polymer backbone via a short spacer or with one carbon-carbon single bond. With
further understanding of these LC polymers (LCPs), side chains of MJLCPs can also
be bulky ones that are not mesogenic.
30
Z. Shen
the first MJLCPs have laterally attached mesogenic side chains, bulky side chains
that are not mesogenic can also be used to construct MJLCPs. The “jacketing” effect,
i.e., the steric hindrance caused by the densely packed side chains, forces the polymer
backbone to take an extended-chain conformation. Many factors, such as MW,
backbone flexibility, tail length, and architecture, influence the phase behaviors of
MJLCPs. With the understanding of the chemical structure-phase behavior relationships, molecular design for MJLCPs can be executed by carefully choosing molecular parameters including the shape and rigidity of the side chain, the structure of the
polymer backbone, and so on. MJLCPs can be synthesized by radical polymerizations that do not require highly pure solvents and reagents. Many controlled/living
radical polymerization methods, such as nitroxide-mediated radical polymerization
(NMRP) and atom transfer radical polymerization (ATRP), can also be employed.
Recently, another living polymerization method, ring-opening metathesis polymerization (ROMP), has been applied in the synthesis of MJLCPs with a polynorbornene
backbone. With the use of such controlled polymerization methods, the length of the
rodlike or sheetlike MJLCP chain can be tuned by adjusting the MW. In addition,
MJLCPs can also be synthesized by polymer reactions from prepolymers like poly
(methylsiloxane)s. Furthermore, MJLCPs can also be obtained by taking advantage
of supramolecular chemistry, with the application of hydrogen bonding, ionic interaction, and other non-covalent interactions. Future directions in the study of MJLCPs
will be to address the main challenges by designing monomers that can be more
easily synthesized and polymerized, establishing cost- and time-saving synthetic
methods, applying calculation and computer simulation that can accurately predict
phase behaviors and guide molecular design, and developing functional MJLCP
materials.
Keywords
Mesogen-jacketed liquid crystalline polymer · “Jacketing” effect · Liquid
crystalline phase · Columnar phase · Smectic phase · Structure-property
relationship · Free radical polymerization · Controlled/living radical
polymerization · Nitroxide-mediated radical polymerization (NMRP) · Atom
transfer radical polymerization (ATRP) · Reversible addition-fragmentation chain
transfer (RAFT) · Ring-opening metathesis polymerization (ROMP)
Definition
Mesogen-jacketed liquid crystalline polymers (MJLCPs) are side-chain polymers
that have significant chain rigidity and form liquid crystalline (LC) phases. The first
MJLCPs have laterally attached mesogenic side chains that are connected to the
polymer backbone via a short spacer or with one carbon-carbon single bond. With
further understanding of these LC polymers (LCPs), side chains of MJLCPs can also
be bulky ones that are not mesogenic.
30
Z. Shen