Side-chain liquid crystalline polymers polysiloxane

The concept of a side chain liquid crystal polymer has been demonstrated in a number of laboratories and is well documented in the literature (J ). Most of the side chain liquid crystalline polymers reported to date contain polysiloxane, polyacrylate or polymethacrylate main chains. More recent studies on the effect of backbone flexibility now include the use of flexible poly(ethylene oxide) or more rigid poly( a-chloroacrylate) chains. 

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.

Synthesis and mesomorphic properties of the first ferrocene-containing side-chain liquid crystalline polymers, 69, obtained by grafting either a 1,1 - or a 1,3-disubstituted ferrocene derivative functionalized by a vinyl group onto a polysiloxane have been reported [155J. These polymers showed enantiotropic SmC and/or SmA mesophases. 

The mesogenic behavior of 43 emphasizes the role played by the oc-tasilsesquioxane core when comparing with the related side-chain liquid-crystalline polysiloxanes [95,96]. It is remarkable that the thermal stability of the chiral nematic phase is similar in both the polymer and the dendrimer, suggesting that the cubic core does not perturb significantly the associations between the mesogens necessary to support the chiral nematic phase. 

Chang-Chien, G., Terminally carboxyl oligo(ethylene oxide) monomethyl ether-substituted side chain liquid crystalline polysiloxane polymer as stationary phase in capillary gas chromatography for the separation of polynuclear aromatic hydrocarbons, J. Chromatogr. A, 808, 201-209, 1998. 

Figure 23. Left Global and TS experiments obtained for a side-chain liquid-crystalline polysiloxane (data adapted from [177, 178], where more details are given), where at least three distinct relaxation processes can be found. Right Activation energy as a function of the temperature of the maximum of TS peaks obtained for the same polymer at different polarization temperatures, using r = 2 °C. The activation energy was calculated from the activation enthalpy, as reported in [177].

H J Coles and R Simon. Electro-Optic Effects in a Smectogenic Polysiloxane Side Chain Liquid Crystal Polymer, in "Recent Advances in Liquid Crystalline Polymers", L L Chapoy (ed),... 

Meng, F. Lian, J. Zhang, B. Sun, Y., Chiral Side-Chain Liquid-Crystalline Polysiloxanes Bearing Fluorinated Mesogens and Cholesteryl Groups. Eur. Polym. J. 2008, 44, 504-513. 

Lee, K.-J. Hsiue, G.-H. Wu, J.-L. Sha, Y.-A., Molecular Structure of Side-Chain Liquid Crystalline Polysiloxane in the Smectic C Phase from X-Ray Diffraction and Molecular Modeling Polymer 2007,48,5161-5173. 

Gray, G. W., Synthesis and properties of side chain liquid crystalline polysiloxanes, in Side Chain Liquid Crystal Polymers (C. B. McArdle, ed.), Blackie, Gla.sgow, 1989, pp. 106-129. 

Deschenaux and co-workers also isolated liquid crystalline polysiloxanes containing ferrocene in their side chains.236 These polymers contained either 1,3- or l,l -disubstituted ferrocene and were synthesized from the reaction of preformed polysiloxanes and vinyl organo-iron monomers. 

The side chain polysiloxane liquid crystalline polymers PI, P2 and P3 composed of the above three ferroelectric liquid crystals as the side groups exhibit the ferroelectric liquid crystal phase, their chemical formulae being respectively. 

Thus, the subject of the review are linear and cyclolinear etement-organic polymers forming a spedfic type of the mesophase state. The structure of the mesoj iases and the formation of liquid crystalline macromolecules, in wiiidi classical mesogens in the main or side chains are linked by flexible polysiloxane or poly-phosphazene spacers are similar to the liquid-crystalline polymers with organic spacers. Structure and properties of these polymers have been reviewed recently and, therefore, will not be considered in our article. 

Figure 4 The dielectric loss tangent of the liquid crystalline polymer of the polysiloxane main chain (the number of silicon is 31) and 4-cyanophenyl-4-propyloxy benzoate side chain (the number is 14, this polymer is named LCPP) dissolved in phenyl-substituted polydimethylsiloxane (Ph-PDMS, 15% phenyl content) as a function of frequency obtained at 20-60 "C. Reproduced with permission from T. Hao, A. Kawai, and F.lkazaki, J. Colloid and Interface Sci., 239(2001)106...

The author s group chose polyacrylate [102, 103], polyoxyethylene [104, 105], polysiloxane [103], and a polyacrylate/polysiloxane hybrid polymer [106] as the main chain according to the design in Fig. 1.26b-e. We attached various kinds of side-chain structures onto polymer main chains described above and checked the physical properties of these side-chain-type ferroelectric liquid crystalline polymers (FLCPs). 

Engel M, Hisgen B, Keller R, Kreuder W, Reck B, Ringsdorf H, Schmidt HW, Tschmner P (1985) Synthesis, structure and properties of liquid crystalline polymers. Pure Appl Chem 57 1009-1014 Finkelmann H (1982) Polymer Liquid Crystals. Academic ftess. New York Finkelmann H, Rehage G (1980) Investigations on liquid crystalline polysiloxanes, 1. Synthesis and characterization of linear polymers. Makromol Chem Rapid Commun 1 31-34 Finkelmann H, Rehage G (1984) Liquid crystal side chain polymers. Liquid crystal polymers II/III. Adv Polym Sci 60/61 99-172... 

Liquid crystalline imprinted materials have been synthesized (Fig. 24) from polysiloxanes with mesogenic side-chains. In some of them, acetophenone was chosen as template and was covalently linked to the mesomorphous network via a ketal link [ 199]. In the others, the templates (carbobenzoxy-L-phenylala-nine, 1,8-diaminonaphthalene or theophylline) were in interaction with the mesomorphous polymer via hydrogen bonding [200]. All the imprinted networks were obtained as dense membranes. 

The liquid crystalline side chain polymers investigated have either a polysiloxane (compounds SiCl and SIGN) or a polyacrylic (compound AcCN) polymer chain. These are coupled via flexible spacers with the mesogenic p-substituted benzoic acid phenylester groups. SiCl and SiCN are copolymers with p-methoxy components in excess. 

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