Synthesis of liquid-crystalline polymers

Synthesis of Liquid-Crystalline Polymers with Mesogenic Side Groups. 177... 

Recently, researchers have foimd successful routes to the formation of highly monodisperse liquid crystalline polymers with well defined structures via direct polymerization of the mesogens -. In particular, anionic polymerization is very attractive and allows synthesis of liquid crystalline polymers with well-defined structures, high stereoregularity, and a uniform chain length. In addition, living anionic polymerization is... 

Fig. 1 Synthesis of liquid crystalline polymer networks (x,y,z are the numbers of monomer units of one polymer chain x+y+z = 120 m is the number of methylene units of the flexible spacer)...

Investigation and Synthesis of Liquid Crystalline Polymers by Thin Film Polymerization... 

INVESTIGATION OF THE EFFECTS OF REACTION CONDITIONS ON THE SYNTHESIS OF LIQUID CRYSTALLINE POLYMERS... 

The contents of the project include (1) Synthesis of liquid crystal materials and its evaluation, (2) Synthesis of liquid crystalline polymers (LCP) and its evaluation,... 

Research Focus Synthesis of liquid crystalline interpenetrating polymer networks using photocrosslinkable mesogenic monomers. 

The development is reviewed of liquid-crystalline polymers whose mesophase formation derives from the nature of the chemical units in the main chain. The emphasis lies primarily on highly aromatic condensation polymers and their applications. The general properties of nematic phases formed by such polymers are surveyed and some chemical structures capable of producing nematic phases are classified in relation to their ability to form lyotropic and thermotropic systems. The synthesis, properties, physical structure and applications of two of the most important lyotropic systems and of a range of potentially important thermotropic polymers are discussed with particular reference to the production and use of fibres, films and anisotropic mouldings. 

Finkelmann, H., Koldehoff, J., Ringsdorf, H. 1979. Synthesis and Characterization of Liquid-Crystalline Polymers with Cholesteric Phase. Angew. Chem. Int. Ed. Engl. 17, 935... 

This paper presents some of our results on the synthesis and structure of thermotropic main-chain liquid crystalline polyethers based on bis(4-hydroxy-phenoxy)-p-xylene. It also deals with two areas in the field of liquid crystalline polymers that have received only little attention, namely the dielectric relaxation (5-10 and Gedde, U.W. Liu, F. Hult, A. Gustafsson, A. Jonsson, H. Boyd, R.H. Polymer submitted) and the kinetics of isotropic-mesomorphic state transitions (11-14. 32). They are both very important for the understanding of the nature of the mesomorphic state in polymers and for the understanding of similarities and differences of physical phenomena between liquid crystalline and semi-crystalline polymers. 

Synthesis. The main demand for the synthesis of this new type of liquid crystalline polymer is a high conversion and the absence of any side reactions for both reaction steps. For the first investigations described in this communication IR-spectroscopy was used to determine the conversion. The molecular weight distribution obtained from gel permeation chromatography (GPC) is used to monitor side reactions. 

Some polymers manifest liquid crystalline ordering, which does not have the full long-range three-dimensional periodicity of crystallinity but is far more ordered than amorphicity. Since many excellent books and articles have been published on such polymers and the author does not have much that is new to add to this background information, very little will be said about polymer liquid crystallinity in this book. Van Krevelen [3] has reviewed liquid crystallinity in polymers in a readable manner and discussed its effects on properties for which quantitative structure-property relationships are available. Adams et al [41] have published a valuable compendium of articles covering the theory, synthesis, physical chemistry, processing and properties of liquid crystalline polymers. Woodward [42] has discussed and illustrated liquid crystallinity in polymers with many beautiful micrographs. 

Carswell, R.. Cormack, P Sherrington, D and Moore. B,. Solid phase synthesis of liquid crystalline oligopeptides, RSC Polymer Symposium Wilton (1996). 

FIGURE 11.12 Photomicrographs of the nematic Schlieren texture that can be observed using a polarizing microscope. (Reproduced from Noel, C., Synthesis characterization and recent developments of liquid crystalline polymers, Makromol. Chem. Macromol. Symp., 22, 95, 1988. With permission.)... 

Noel, C., Synthesis characterization and recent developments of liquid crystalline polymers, Makromol. Chem. Macromol. Symp., 22, 95, 1988. 

H.Finkelmann, J.Koldehoff, and H.Ringsdorf, Synthesis and characterization of liquid crystalline polymers with cholesteric phase, Angew.Chem.Int.Ed.Engl. 17 935 (1978). 

Sawada, Y. Tomita, I. Rozhanskii, I.L. Endo, T. Synthesis of liquid crystalline organometallic poly(aryl-ene)s containing 1,3-type ((r " -cyclobutadiene)cobalt moieties in the main chain. J. Inorg. Organomet. Polym. 2000. 10 (4). 221-230. 

B. Synthesis of Liquid-Crystalline Hybrid Polymers Using POSS as a Component of Copolymerization ... 

Chemical Structures and Synthesis. A variety of chemical structural units are available for use in the design and synthesis of liquid crystalline pol3nners. Flexible main chain pol3nners are depicted below in schematic form along with examples of chemical subunits. Rigid main chain polymers lack the flexible segment D. 

Ringsdorf and his group have reported the synthesis and thermal characterization of liquid crystalline polymers with methacrylate and acrylate backbones in which the mesogenic groups are in pendant side chains.2,9,11 Some of their results are shown in Figure 6. 

H Ringsdorf and A Schneller. Synthesis, Structure and Properties of Liquid Crystalline Polymers. Brit.Pol.J. 13 43 (1981). 

Wittmann JC, Lotz B (1985) Polymer decoration the orientation of polymer folds as revealed by the crystallization of polymer vapors. J Polym Sci, Polym Phys Ed 23 205-211 Wunderlich B, Grebo wig J (1984) Thermotropic mesophases and mesophase transitions of linear, flexible macromolecules. Adv Polym Sci 60/61 1-59 Zhou QF, Li HM, Feng XD (1987) Synthesis of liquid-crystalline polyacrylates with laterally substituted mesogens. Macromolecules 20 233-234... 

Figure 3.13 Reaction scheme for synthesis of liquid crystalline epoxy by chemical modification of DGEBA resin. Reprinted with permission from K. Sadagopan, D. Ratna and A.B. Samui, Journal of Polymer Science Part A Polymer Chemistry Edition, 2003, 41, 3375 2003, John Wiley and Sons Publishers...

Polymethylsiloxane (PMS) materials with ID (PDMS) or 2D/3D (PMS) siloxane backbone have drawn considerable fundamental and technological interest because of their applications as components of nanocomposites, copolymers for synthesis of ion conducting polymeric materials, chromatographic adsorbent, a component of medicinal preparations (e.g., Cleocin, Universal Washaid, United States), implants, adjuvant Capsil (Aquatrols, USA Scotts, USA), a vaccine adjuvant, etc. Additionally, PMS in the form of hydrogel (CpMs 10 wt%) is utilized as a medicinal enterosorbent Enterosgel (Kreoma-Pharm, Ukraine). Functionalized PMSs are used for modification and functionalization of solid surfaces. They are also used as supports for catalysts, or as polymer backbones for preparation of liquid crystalline polymers. 

The synthesis and mesogenic behaviour of many liquid crystalline polymers has been published however, in the vast majority of cases the molecular weights and polydispersities have not been determined. Accordingly, there are difficulties in truly relating mesogenic behaviour to polymer structure. The synthesis of liquid crystal polymers is considered in Chapter 8. 

The next step was the synthesis of liquid crystalline polysiloxanes with oxadiazole groups in the mesogenic unit. The polymers were prepared by a polymeranalogous reaction of the monomers 10 and 11 with poly(hydrogenmethylsiloxane) 15. 

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