Main-chain liquid-crystalline 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... 

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. 

Identification of Highly Ordered Smectic Phases in a Series of Main-Chain Liquid-Crystalline Polyethers... 

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. 

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. 

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. 

Percec V, Shaffer TD, Nava H (1984) Functional polymers and sequential copolymers by phase transfer catalysis. 10. Polyethers of mesogtmic bisphenols a new class of main-chain liquid crystalline polymers. J Polym Sci Polym Lett Ed 22 637-647... 

---