Synthesis and characterization of some new main-chain liquid crystalline polymers with tetrakis(oxyethylene) and decamethylene spacers

Abstract

Two series of liquid crystalline, main-chain polyesters were synthesized having mesogenic triads based on substituted hydroquinones to form the center of the triad and two residues of p-hydroxybenzoic acid at either side. The two series differed only in the nature of the spacer; in one series it was the decamethylene and in the other the tetrakis(oxyethylene) unit. Both the type of lateral substituent and the type of spacer had a profound influence on the mesogenic properties compared to that of the unsubstituted polymer. The methyl substituent increased the temperature range of the mesophase. The ethyl substituent had a similar effect for the polymer with the decamethylene spacer, but its presence led to a marked decrease in the thermotropic properties for the polymer with the poly(oxymethylene) spacer.

Synthesis and characterization of novel organosoluble polyesters based on a DIOL with azaquinoxaline ring

“…However, limitations arise from their high melting temperature and limited solubility in most organic solvents 1–3. To obtain polyesters with considerably improved processing properties; several chemical modifications including: (i) the introduction of bulky, or nonsymmetrical substituents; (ii) the use of flexible spacer; (iii) the use of nonlinear or bent monomers; and (iv) copolymerization of different monomers have been previously reported 4–13. A number of thermally stable aromatic polyesters have been prepared,14–23 but in general the types of structures that impart thermal resistance also result in poor processing characteristics.…”

Influence of the monomer feeding sequence on the structure and properties of thermotropic liquid‐crystalline poly(ester imide)s

“…A large amount of work has been done to prepare thermotropic liquid‐crystalline (LC) poly(ester imide)s by Kricheldorf's and Lenz's groups since 1987 2–11. Yet, to the best of our knowledge, nearly all the reported poly(ester imide)s with higher molecular weights have been synthesized by the melt transesterification approach at high temperatures under reduced pressure 12.…”

Effect on TSDC relaxation spectra of substitutions in the mesogenic unit and in the flexible spacer of poly(tetramethylene terephtaloyl-bis-4-oxybenzoate)

“…[1][2][3][4][5] Depending on polarity and size of the substituents, not only the thermotropic behavior but also the nature of the mesophases formed may be affected. The correlation between these structural aspects and the liquid-crystal character of these polymers is of extraordinary importance for their technological applications due to the enhancement in processability and, very recently, the possibility of blending them with highperformance thermoplastic polymer matrices.…”