Liquid crystalline polymers hydrogen bonding

Figure 5.9 Examples of supramolecular side chain liquid crystalline polymers (SSCLCPs) based on hydrogen bonding (6 and 7) and coulombic interactions and hydrogen bonding (8).

It is reasonable to assume that the complementary units form the expected triply hydrogen bonded pairs, so that the entirely different behaviour of the pure compounds and of the 1 1 mixtures may be attributed to the spontaneous association of the complementary components into a polymolecular entity based on hydrogen bonding. The overall process may then be described as the self-assembly of a supramolecular liquid-crystalline polymer based on molecular recognition (Figure 40). The resulting species (TP2, TU2) is represented schematically by structure 174. 

SchetnelO Examples of hydrogen-bonded side-chain liquid-crystalline polymers [92,241, 242]... 

Side-chain liquid-crystalline polymers were also prepared using double hydrogen bonds (Scheme 11) [243]. All these examples have in common a flexible spacer connecting the mesogenic unit to the polymer backbone. That this is not always required is demonstrated by yet another class of supramolecular hquid-crystalhne polymers obtained by hydro-... 

High resolution solid-state NMR spectroscopy is also a very powerful method for characterizing the solid structure and the local motion of different solid polymers. We recently characterized the crystalline-noncrystalline structure for different crystalline and liquid crystalline polymers, such as polyolefins [7-12], polyesters [13-15], polyether [16], polyurethanes [17, 18] and polysaccharides, including cellulose [19-29], amylose [30, 31] and dextran [32]. On the basis of these analytical methods, we also investigated the intra- and intermolecular hydrogen bonds of PVA in both crystalline and noncrystalline regions as well as in the frozen solution state. In this chapter. 

The formation of covalent cross-linking in liquid-crystalline polymers is useful to lock in the molecular order in solid states, which leads to static functionality [114, 115]. For hydrogen-bonded mesogenic networks, the use of the dynamic nature of H-bonding induces dynamic properties [108, 109]. It is important to choose an appropriate method of cross-linking for the purpose of the use of network materials. 

Fig. 19. Hydrogen-bonded liquid-crystalline polymer blend...

The topic of hydrogen bonded liquid crystalline materials has been reviewed by several groups [2,27,29-31]. Herein only the important and recent development on hydrogen bonded supramolecular low molecular weight LCs will be introduced. Supramolecular liquid crystalline polymers will not be included in this chapter. 

Kato T, Hirota N, Fujishima A, Frechet JMJ. 1996. Supramolecular hydrogen bonded liquid crystalline polymer complexes. Design of side chain polymers and a host guest system by noncovalent interaction. J Polym Sci A 3 57 62. 

Viswanathan S, Dadmun MD (2004) Miscible blends containing a liquid crystalline polymer via optimized hydrogen bonding correlation to theory. J Polym Sci B Polym Phys 42 1010-1022... 

Viswanathan S, Dadmun MD (2003) Optimizing hydrogen-bonding in creating miscible liquid crystalline polymer blends by structural modifications of the blend components. Macromolecules 36 3196-3205... 

Figure 23 Supramolecular side-chain liquid crystalline polymers 39-43 representing three classes of side-chain functionaiization (a) polyactylate-based side-chain SPs with mesogen formed through complexation (b) polysiloxane-based side-chain SPs with mesogen formed through complexation, and (c) conjugation of a mesogen via hydrogen bonding to a traditional covalent polymeric backbone.

Scheme 8. Generation of nonsymmetrical liquid crystalline dimers, twin dimers and side chain liquid crystalline polymers by specific hydrogen bonding interactions.

DESIGN OF NEW TYPE OF LIQUID CRYSTALLINE POLYMERS THROUGH INTERMOLECULAR HYDROGEN BONDING... 

Schematic illustration of the structure of a typical side-chain LC polymer is shown in Scheme I. Mesogenic units are covalently attached to the polymer backbone via a flexible spacer.Our aim in the present study is to construct new type of side-chain liquid crystalline polymers through intermolecular hydrogen bonding in place of covalent bonding. Hydrogen bonding may be used to connect the part where the broken line shows in Sceme I. We describe self-assembly of LC polymers through selective recognition between a polymer side chain and low-molecular-weight molecules.

A Novel Structure of Side-Chain Liquid Crystalline Polymer Built through Intermolecular Hydrogen Bonding... 

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