Liquid crystalline polymers crown ethers

Percec and Rodenhouse presented the first main-chain liquid crystalline polymer with a crown ether moiety in the backbone of the polymer [83], Liquid crystalline polyethers 63 were obtained by phase transfer catalyzed polyetherification of... 

LIQUID CRYSTALLINE POLYMERS CONTAINING CROWN ETHERS AND POLYPODANTS... 

Figure 12. The molecular architecture of liquid crystalline polymers containing crown ether ligands.

Fig. 4. Examples of organic molecules that are able to recognize each other to form supermolecules (a) individual crown ether molecules coordinated with selected metal cations [14] (b) supramolecular assembly to form oligomeric liquid crystals based on three hydrogen bonds [74] (c) supramolecular assembly to form a polymer-like chain (according to Lehn et al. [80]) supramolecular assembly to form side-chain liquid-crystalline polymers using (d) one hydrogen bond (according to Kato and Frechet [76]) (e) two hydrogen bonds (according to Kato et al. [77]) and (f) ionic complexation (according to Bazuin and Tork [78]).

A variety of polymers containing liquid crystalline crown ethers of the molecular shape discussed in this section is known throughout the literature, most of which originate from Percec s laboratory. 

Scheme 11 Liquid crystalline crown ether polymer poly(22)...

A variety of other liquid crystalline crown ether containing polymers were synthesized, all possessing the same mesophase-stabilizing effect of polymerization (polymer effect) [38, 39]. 

Most interesting are the effects of salt complexation on the mesomorphic behavior of liquid crystalline crown ethers and liquid crystalline crown ether polymers. Sodium triflate was added to poly(17) [34] and poly(25) (Scheme 14) [39]. The enantiotropic nematic and smectic phases of poly(17) were changed dramatically [40]. With increasing amounts of salt, the clearing temperatures are shifted to higher values while the melting transition increases only slightly. 

Scheme 14 Complexation of liquid crystalline crown ether polymers poly(17, 25)...

Commonly, polymers with a poly(siloxane) backbone and pendant side chain liquid crystalline groups are used. The side chain liquid crystalline groups are organic complexes with zinc, nickel, or crown ethers. This type of polymers is addressed as mesomorphic poly(siloxane). Side chains based on 4-biphenyl-4-allyloxybenzoate exhibit a special separation performance for racemic compounds. ... 

Stroganov V, Ryabchun A, Bobrovsky A, Shibaev V (2012) A novel type of crown ether-containing metal ions optical sensors based on polymer-stabilized cholesteic liquid crystalline films. Macromol Rapid Commun 33 1875-1881... 

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