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Mesogen-Jacketed Liquid Crystalline Polymers: Molecular Design and Synthesis

  • Zhihao ShenEmail author
Living reference work entry

Abstract

Mesogen-jacketed liquid crystalline polymers (MJLCPs) are rigid side-chain polymers that can form columnar and smectic liquid crystalline (LC) phases. Their liquid crystallinity is dependent on the molecular weights (MWs), and many MJLCPs exhibit reentrant phase behaviors. The size of the structure formed by an MJLCP, 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) 

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Beijing National Laboratory for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center for Soft Matter Science and Engineering, College of Chemistry and Molecular EngineeringPeking UniversityBeijingChina

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