New polymer syntheses. 102. Aspirin-modified LC polyesters based on PET and 4-hydroxybenzoic acid

Abstract

Four series of liquid‐crystalline copolyesters were prepared by the transesterification of poly(ethylene terephthalate) (PET) with 4‐acetoxybenzoic acid (4‐ABA) or mixtures of 4‐ABA and acetylsalicylic acid (ASA). Two series consisted of 30 mol % PET, and the other two series consisted of 40 mol % PET. The molar ratio of 4‐HBA and ASA was varied in all four series from 0 to 25 mol %. One 30% PET series and one 40% PET series were prepared with the addition of acetic acid, which caused a more perfect randomization of the sequence but yielded slightly lower molecular weights. The incorporation of ASA reduced the crystallinity, which vanished completely at a salicylic acid (SA) content greater than 10 mol %. SA also reduced the stability of the nematic phase, but all the copolyesters were thermotropic up to a 20 mol % SA content. Furthermore, the molecular weights decreased with the increasing incorporation of ASA. Despite this negative trend, the melt viscosity and the storage and loss moduli passed a maximum between 5 and 10% SA. Obviously, the incorporation of SA favored the formation of entanglements. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2013–2022, 2000

Synthesis, Dielectric, and Photochemical Study of Liquid Crystalline Main Chain Poly(ester imide)s Containing Cinnamoyl Moieties

“…All copolyesters of this work were prepared with 5% of isosorbide, because all previous studies of isosorbide-containing copolyesters have shown that higher fractions are unfavorable for the formation of a Grandjean texture. ,− Isosorbide is known 29 to possess a high helix twisting power, and obviously, a high molar fraction of isosorbide generates helices with a pitch which is too small for the interaction with visible light. The substituted hydroquinones were selected as diphenols because the para position of the hydroxy groups favors the formation of LC phases and because substituted hydroquinones have proven in previous studies to favor the formation of noncrystalline cholesteric poly(ester imide)s. In contrast, the incorporation of catechol results in amorphous copoly(ester imide)s as expected from similar studies of catechol countaining LC polyesters . The chemical structure and composition of all polyesters were checked by elemental analyses (see Table ) and by IR and 1 H NMR spectroscopies.…”

“…The substituted hydroquinones were selected as diphenols because the para position of the hydroxy groups favors the formation of LC phases and because substituted hydroquinones have proven in previous studies 30 to favor the formation of noncrystalline cholesteric poly-(ester imide)s. In contrast, the incorporation of catechol results in amorphous copoly(ester imide)s as expected from similar studies of catechol countaining LC polyesters. 31 The chemical structure and composition of all polyesters were checked by elemental analyses (see Table 2) and by IR and 1 H NMR spectroscopies. The elemental analyses showed the greatest difference of calculated and experimental values for the C atoms.…”

Review on: liquid crystalline polyazomethines polymers. Basics, syntheses and characterization

“…In the last few decades, many MC-LCPs and SC-LCPs have been synthesized and investigated [48][49][50][51][52][53][54][55][56][57][58][59][60]. These polymers include: polyesters, polyethers, polyamides, polyurethanes, polysiloxanes, polyamines, polythioether, and polyazomethines.…”

Macrocycles 14. Polycondensations of Aspirin and Other Monomers of Salicylic Acid

“…Finally, it should be mentioned that addition of aspirin to copolycondensations of other monomers also resulted in a systematic reduction of the molecular weight. [18] Again the formation of hair-pin conformations and cyclizations is the most obvious explanation.…”