Photoreactive main‐chain liquid‐crystalline polyesters: Synthesis, characterization, and photochemistry

Abstract

Three series of semiflexible and rigid main-chain polyesters containing photoreactive mesogenic units derived from p-phenylenediacrylic acid (PDA) and cinnamic acid have been synthesized by high-temperature polycondensation. The thermal and mesomorphic properties of the polymers have been determined. The photochemical behavior of polymer P-[1]-T, which contains a PDA unit, has been studied both in solution and in films. In solution, [2þ2] photocycloaddition, E/Z photoisomerization, and photo-Fries rearrangement can take place. In contrast, the dominant process in spin-coated films is the [2þ2] photocycloaddition reaction, which causes crosslinking of the polymer. In films, the photochemistry and induction of anisotropy are strongly influenced by the aggregation of the PDA phenylester unit. A dichroism of about 0.2 has been induced in films by irradiation with linearly polarized UV light, and thus the capability of these films to induce optical anisotropy and align liquid crystals has been demonstrated. Liquid-crystalline cells have been made with polarized irradiated films of P-[1]-T as aligning layers. A commercial liquidcrystalline mixture has been used for this study, and a similar liquid-crystalline order determined by polarized Fourier transform infrared to a commercial cell with rubbed polyimide as an aligning layer has been detected. Because of crosslinking of the irradiated P-[1]-T photoaligning layer, the photoinduced anisotropy is stable at high temperatures, and the liquid-crystalline molecules are insoluble in the irradiated polymer. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4907-4921, 2005

Study of green epoxy resins derived from renewable cinnamic acid and dipentene: synthesis, curing and properties

“…CA derivatives were used as building blocks to improve the properties of some polyesters in the literature. [34][35][36][37] Semi-exible and rigid main-chain polyesters containing photoreactive mesogenic units derived from CA were synthesized by hightemperature polycondensation. 35 In addition, CA-derived amidoamines, polyamides or amine adducts were used to cure the epoxy binders in the literature.…”

Synthesis and properties of new aromatic copolyesters containing phosphorous cyclic bulky groups

“…The objectives of designing melt processable polyesters with nematic structure are to reduce the melting temperature bellow the thermal stability limit and to obtain a melt that remains nematic until the onset of decomposition. The structural modifications that are commonly used to control the T m values of this class of polymers include the following: copolymerization of different sizes of mesogenic (LC forming) monomers to lower the symmetry of the polyester primary structure; the introduction of substituents of various sizes on either the aromatic dicarboxylic acid, the aromatic diol or both moieties to disrupt lateral packing; the introduction of noncoplanar 2,2 0 -substituted-4,4 0 -biphenols and 2,2 0 -substituted-4,4 0 -biphenylenedicarboxylic acids, and other structurally similar monomers to cause a reduction of inter-chain interactions; the introduction of kinked or bent (nonlinear) monomers to lower the persistence length of the polyester in the LC phase and to disrupt lateral interactions in the solid state [6][7][8][9][10][11][12].…”

Investigation on dual properties of photosensitive thermotropic liquid‐crystalline poly(benzylidene‐ether)s containing alkanones and methylene spacers in the main chain

“…The stretching vibration at 1581 cm −1 is attributed to exocyclic olefinic double bond (CC) group 43. The CH bending of olefinic carbon at 980 cm −1 proved the existence of the E configuration,44 and it was further supported and confirmed from the 1 H NMR study. All the polymers showed strong absorptions around 2953 and 1510 cm −1 due to methylene hydrocarbon spacer in the main chain and the aromatic ring CC stretching, respectively.…”