Polyethers, liquid crystalline

Polyetherimides show no crystallinity as evidenced from calorimetry measurements. The heteroarylene like phenylquinoxaline [27], oxadiazole [30], and benzoxa-zole [56] activated polyethers show TgS from DSC thermograms, with no evidence of crystallization, indicating amorphous or glassy morphology. Furthermore, wide angle x-ray scattering measurements show no evidence of crystalline or liquid crystalline type morphologies, consistent with an amorphous structure. F polyether... 

Percec et al. have described the possibility of making hyperbranched polymers which exhibit liquid crystalline phases [34, 35]. They made hyperbranched polyethers based on an A B monomer having both a spacer and a... 

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. 

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... 

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]. 

Ortho-substitution is also used to prepare branched liquid crystalline polyethers of 3,4-(di-n-alkoxy)benzyI derivatives in which the cyclotetraver-atrylene disc-like mesogen is formed in situ during the polymer-forming Friedel-Crafts alkylation, [30-32],... 

Most of the liquid crystalline main-chain polymers synthesized are polyesters. For the present study where isothermal phase transition kinetics studies should be performed, this was a less suitable alternative since they undergo thermally induced reactions, i. e. transesterifications, and for this reason instead polyethers were chosen. Polyethers also have other advantages like lower transition temperatures and higher solubilities. 

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. 

The temperature independent relaxation time (t0) is also affected by the spacer length. The data of the liquid crystalline main-chain polyethers are in agreement with the data by Farrow et al. (291 on semicrystalline poly(methylene terephthalate) polymers. 

Various liquid crystalline copolyesters (LCP s) were used depending on the particular thermoplastic matrix which was selected. In this work three high performance matrices were used polyether-... 

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

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 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-... 

Organometallic polyurethanes containing backbone polyether units have been reported.184,185 The incorporation of ferrocenyl segments into the backbone of polyurethanes enhanced thermal stability.186 There have been a number of studies on the incorporation of ferrocenyl units into the backbone of polyesters 101.187-191 A number of polymers of this class exhibited liquid crystalline properties.189-192 The thermal stability and glass transition temperatures of these polymers decreased with an increase in the length of the alkyl chains. 

The Mesogenic Index has been applied to a substantial body of data on polyesters and polyamides drawn from from published literature including 22 systems where the critical concentration for onset of liquid crystallinity has been established with reasonable accuracy (Tables 2 and 3). The characteristic value of the MI at the onset of a liquid crystalline phase is generally found to be remarkably close to 10. When applied to the more limited data available on polyurethanes, polyethers, polycarbonates, the rule holds up well. 

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