Polyether thermotropic

LC polyesters belong to the class of thermotropic main-chain LCPs, which also comprises polymers such as polycarbonates, polyethers, polyphenylenes, polyester-imides, polymers containing azo- or azo V-oxide linking groups, some cellulose derivatives, and polypeptides such as po 1 y (y - be n zy 1 -1. - g 1 u tamate). Both from the academic and industrial points of view, polyesters are by far the most important representatives of this class of polymers. 

L. Rozes, Synthese de poly(polyester-bloc-polyether)s thermotropes. Approche des proprietes thermiques, viscoelastiques et rheologiques, These, de l Universite P. et M. Curie, Paris, 1996. 

Some particularities of the extraction of ions from an aqueous organic phase, and of the phase catalyzed polyetherification will be summarized. These will represent the fundamentals of our work on the synthesis of some novel classes of functional polymers and sequential copolymers. Examples will be provided for the synthesis of functional polymers containing only cyclic imino ethers or both cyclic imino ethers as well as their own cationic initiator attached to the same polymer backbone ABA triblock copolymers and (AB)n alternating block copolymers and a novel class of main chain thermotropic liquid crystalline polymers containing functional chain ends, i.e., polyethers. 

Three major topics of research which are based on phase transfer catalyzed reactions will be presented with examples. These refer to the synthesis of functional polymers containing functional groups (i.e., cyclic imino ethers) sensitive both to electrophilic and nucleophilic reagents a novel method for the preparation of regular, segmented, ABA triblock and (A-B)n alternating block copolymers, and the development of a novel class of main chain thermotropic liquid-crystalline polymers, i.e., polyethers. 

Recently we have developed a new class of thermotropic liquid crystalline (LC) main-chain pol3rmers, i.e., polyethers of mesogenic bis-phenols(16-17.23-26). Since the obtained polymers are not soluble in dipolar aprotic solvents, the only available synthetic avenue for their preparation consists in the phase transfer catalyzed polyetherification. 

Recently much effort has been made to induce liquid crystallinity in polyimides. Kricheldorf et al., Chen et al., and Sato et al. have suggested that an aromatic im-ide ring may be an excellent mesogen through their studies on thermotropic liquid-crystalline polyimide-esters [41-54] and polyimide-carbonates [55, 56]. Some thermotropic properties of aromatic polyether-imides have also been reported by Asanuma et al. [57]. 

Thermotropic Main-Chain Polyethers Based on Bis (4-hydroxy phenoxy) -p-xylene... 

JONSSON ETAL. Thermotropic Main-Chain Polyethers... 

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. 

Kinetics of Phase Segregation in Thermotropic Liquid-Crystalline Copolyester and Polyether Imide Blends... 

The first thermotropic liquid-crystalline dendrimer, 15, shown in Fig. 17, was reported by Percec and Kawasumi for a hyperbranched polyether structure that consisted of an AB2 monomer, with a mesogenic unit based on confer-... 

Within the extensive literature on this subject, there are many examples of the synthesis of thermotropic polyesters, polyesteramides, polycarbonates, polyethers, polyurethanes and polyester-imides. Until recently, the main omissions had been thermotropic polyamides and polyimides however, many examples of polyamides that show lyotropic behaviour have been known for a long time. 

One of the main features of nonionic water-soluble cellulose derivatives is that they exhibit, like some other polyethers, an inverse solubility-temperature behavior, i.e. there is phase separation on heating above the so-called lower critical solution temperature (LCST). The temperature at which a polymer-rich phase separates is normally referred to as the cloud point (CP). For ideal solutions, this temperature corresponds to the theta-temperature. Actually, for some derivatives, the cloud point may be preceded, if the concentration is not too low, by a sol-gel transformation with an increase in viscosity and possibly formation of liquid crystals (see Sect. 3.5). As it will be seen later, this reversible thermotropic behavior may be detrimental to the performance of the derivatives or can be advantageneously utilized to develop applications. 

Polyether dendrimer (thermotropic) Dibromalkanes with 1-(4-hydroxy-4 -biphenylyl-2-(4-hydroxyphenyl) 6-10 methylene units as flexible spacers those with 6, 8, and 10 CH2 units or with benzyl chain end exhibit nematic mesophase. [108]... 

Polyether dendrimers (thermotropic) Monomers 6-bromo-1-(4-hydroxy-4 -biphenylyl)-2-(4-hydroxyphenyl)hexane (TPH) 13-bromo-1 -(4-hydroxyphenyl)-2- [4-(6-hydroxy-2-naphthalenylyl)-phenyl]tridecane (BPNT) 13- bromo-1-(4-hydro-xyphenyl)-2-(4-hydro-4"-p- terphenylyl)tridecane (TPT) Chain ends benzyl or allyl or alkyl. TPH and BPNT show narrow nematic meosphase TPT nematic mesophase extends over 82 °C. Degree of branching for TPT with allyl end is 0.82. [137]... 

THERMOTROPIC POLYETHERS AND COPOLYETHERS A NEW CLASS OF MAIN CHAIN... 

This paper has presented the first set of available information on the synthesis and characterization of a new class of thermotropic liquid crystalline polyiners the polyethers. A brief comparison of the properties... 

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