Decyloxy Benzoic Acid Research Articles

Effect of the Phobic Segregation between Fluorinated and Perhydrogenated Chains on the Supramolecular Organization in Ionic Aromatic Dendrimers

Two novel series of codendrimers constituted by the grafting of poly(propylene imine) PPI-(NH2)16 (G = 3) with aromatic acids substituted with fluorinated and perhydrogenated chains in different proportions have been synthesized and their liquid crystalline properties have been investigated. Series I is generated by the ionic attachment of 4-decyloxybenzoic acid and 4-(1H,1H,2H,2H)-perfluorodecyloxybenzoic acid in different proportions. Series II results from the ionic junction of eight units of 3,4-didecyloxybenzoic acid or 3,4,5-tridecyloxybenzoic acid and eight units of 4-decyloxybenzoic acid or 4-(1H,1H,2H,2H)-perfluorodecyloxybenzoic acid. The liquid crystalline behavior has been investigated by means of differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffractometry (XRD). All codendrimers exhibit smectic A mesomorphism. Besides, two compounds belonging to series I present uncommon mesophases originated by the incompatibility of the fluorinated and perhydrogena...

Temperature-Dependent Raman Study of the Smectic to Nematic Phase Transition and Vibrational Analysis Using Density Functional Theory of the Liquid Crystalline System 4-Decyloxy Benzoic Acid

Room-temperature Raman spectra of the thermotropic liquid crystalline system, 4-decyloxy benzoic acid (4DBA) have been recorded and the experimentally observed bands are assigned by density functional theory (DFT) for the first time. The C-O and C-C stretching and C-H in-plane bending modes of the phenyl ring and C=O stretching modes of the -COOH group are the marker bands for the smectic (S) --> nematic (N) and nematic (N) --> isotropic (I) transitions for this system. The temperature-dependent Raman spectra for these bands in the heating cycle clearly characterize the S-->N and the N-->I transition over a range <1 degree C, which is much better than the earlier range of 23 degrees C for S-->N and 26 degrees C for the N-->I transition. The approximately 773, approximately 807, approximately 881, and approximately 1146 cm(-1) bands disappear, whereas a band at approximately 830 cm(-1) appears at the S-->N transition. The relative intensity of the approximately 1257 and approximately 1280 cm(-1) bands distinguishes the three phases, namely smectic, nematic, and isotropic, in 4DBA. The variation of line width and peak wavenumber of the approximately 1128 and approximately 1168 cm(-1) bands also clearly shows the two transitions. The molecular reorientation at the transition and the effect of local fields present in the liquid crystalline mesophases are also briefly discussed on the basis of changes in intensity, linewidth and peak wavenumber with temperature.

Change of thermotropic properties in liquid crystal with multiple phase transitions: Surface “aging” effect

The effect of surface “aging” on thermotropic properties of polymorphic mesogen, 4-butoxyphenylester of 4-decyloxybenzoic acid (BPEDBA) which exhibits the smectic G, smectic C, smectic A, and nematic mesophases has been investigated. Temperatures of direct and reverse phase transitions and temperature widths of the heterophase regions have been determined with high accuracy. The shift of the phase transition temperatures and change of the temperature widths of the heterophase regions under the influence of surface “aging” have been reported.

Novel Columnar Tetraphenylethenes via McMurry Coupling

Several tetraphenylethenes 2a, 4a–i with lipophilic side chains were synthesized and their mesomorphic properties were investigated. The most promising candidates turned out to be tetrakis[4-(trisalkyloxybenzoyloxy)phenyl]ethenes 4e–i with chain lengths between C7 and C12. Compounds 4 were prepared by a convergent strategy employing a McMurry coupling of 4,4′-dimethoxybenzophenone 1c, followed by demethylation and subsequent esterification of 2c with either 4-decyloxybenzoic acid 3a, 3,4-didecyloxybenzoic acid 3b, or O-alkylated gallic acids 3c–i. Despite the twisting of the central tetraphenylethene moiety compounds 4c–i display hexagonal columnar mesophases according to differential scanning calorimetry (DSC), polarizing microscopy, and X-ray diffraction studies.

Supramolecular liquid crystals containing isoquinoline hydrogen-bonded acceptors

6-Dodecyloxyisoquinoline IS (1) has been synthesized and utilized as a proton acceptor to generate a series of novel mesogenic supramolecules. Two mesogenic supramolecular dimers IS-OBA and IS-COOBA have been constructed from a 1:1 molar ratio of IS complexed either with 4-decyloxybenzoic acid OBA (2) or with 4-decyloxycarbonylbenzoic acid COOBA (3). A kinked mesogenic supramolecular trimer, i.e. a double H-bonded complex (IS)-THDA, has been constructed from a 2:1 molar ratio of IS complexed with 2,5-thiophenedicarboxylic acid THDA (4). The mesogenic properties of the H-bonded complex (IS2)-THDA are compared with those of previously reported H-bonded complexes (C12PS)-THDA and (C12PP2)-THDA consisting of a 2:1 molar ratio of trans -4-dodecyloxy-4-stilbazole C12PS 2 (5) or 4-dodecyloxypyridine C12PP2 (6) with THDA. Significantly, the first isoquinoline-based supramolecular liquid crystals have been built, and their mesogenic properties have been introduced or modified by fused- N -heterocyclic rings.

Preliminary communication - The effects of bending sites on unconventionally shaped hydrogen-bonded liquid crystals

Angular mesogenic structures of hydrogen-bonded supramolecules have been constructed from a 1:1 molar ratio of 3(or 4)-decyloxybenzoic acid, MA (or PA), mixing either with trans-4-alkoxy-3'(or 4')-stilbazoles, CnM (or CnP), or with their analogous N -oxides (CnMO and CnPO) to form the hydrogen-bonded (H-bonded) complexes CnPPA, CnPMA, CnMPA, CnPOPA, CnPOMA and CnMOPA. By controlling the relative bending position of the H-bonded complexes, the variety of supramolecules offer new molecular structures of different linearities. By means of these bending effects we are able to tune the shape of the molecular architecture and thus to modify molecular packing as well as mesogenic properties. New liquid crystalline properties are introduced by the nonlinear effects of molecular geometry, and powder X-ray diffraction (XRD) patterns have confirmed their novel molecular architectures.

Synthesis and thermotropic properties of new discotic 1,3,5-trisubstituteds-triazinetriones obtained by cyclotrimerization of isocyanates

Abstract The synthesis of a number of s-triazine-2,4,6-triones (isocyanurates) by cyclotrimerization of 4-monoalkoxy-, 3,4-dialkoxy-, or 3,4,5-trialkoxyphenyl-, benzyl-, or styryl-isocyanates is reported. The thermal and phase behaviour of the novel compounds were investigated by optical polarized light microscopy and thermal analysis. No mesophase could be observed for any of the precursors except 4-decyloxybenzoic acid. Mesophases of the isocyanurates were observed only in the series containing 3,4-dialkoxyphenyl moieties. A vinylene group between the inner s-triazine ring and the outer phenylene rings gives low melting points and enantiotropic mesophases for C8 and longer alkyl chains. The phenylisocyanurates may exhibit a monotropic mesophase and normally have the highest melting points of the three types, whereas a methylene spacer suppresses formation of a mesophase. According to the textures observed, the mesophases are hexagonal columnar. This will have to be confirmed by X-ray scattering techniques.

Influence of the order parameter and of the director orientation on the surface tension of free nematic films

Abstract A radial hydrodynamic flow in the nematic phase of free, suspended cylindrical films of 4-n-heptyl- and decyloxybenzoic acid and in 4,4′-di-n-heptyl-oxyazoxybenzene has been observed. The flow starts about 7°C before the phase transition into the smectic C phase. Under the same experimental conditions such a hydrodynamic flow is not established in free nematic films of 4-n-heptyl-and octyloxy-4′-cyanobiphenyl, 4,4′-dimethoxyazoxybenzene and N-(4-ethoxybenzylidene)-4′-n-butylaniline after the completion of the transition from the isotropic liquid to the nematic phase. The observed hydrodynamic flow is explained by a non-linear temperature dependence of the surface tension.

Evidence for the "zigzag" model of the smectic-C phase in the liquid crystal 4(')-butoxyphenylester 4-decyloxybenzoic acid (4OP10OB): A high-resolution x-ray study.

We report, for the first time to our knowledge, on high-resolution x-ray scattering measurements of the liquid crystal 4'-butoxyphenylester 4-decyloxybenzoic acid (4OP10OB) with emphasis on the smectic-C phase and the smectic-A to smectic-C phase transition. From angular scans in reciprocal space we found that the smectic-C layer planes undergo a continuous tilt ${\ensuremath{\varphi}}_{p}$ with respect to temperature that can be described either by a Landau-type mean-field theory (which includes a sixth-order term in ${\ensuremath{\varphi}}_{p}$) or by a simple scaling form: ${\ensuremath{\varphi}}_{p}$\ensuremath{\sim}[(${T}_{c}$-T)/${T}_{c}$${]}^{0.44}$, where ${T}_{c}$ is the smectic-A\char21{}smectic-C transition temperature. Simultaneous measurements of the lattice spacing in the smectic-C phase suggest that the molecules do not behave like rigid rods. We found that the diamagnetic part of the molecule strongly couples to the magnetic field and tilts independently of the aliphatic end chains. The end chains are melted and thus maintain an almost-temperature-independent contact angle to the layer planes. Our measurements are consistent with the ``zigzag'' model of Bartolino, Doucet, and Durand.

IR dichroism of individual vibrational bands of liquid crystals in various phase states

Decytoxybenzoic acid was chosen for the investigation. The appearance of two smectic phases, of types "C" and "D" [4], and a nematic phase is observed for this acid, having a long alkyl chain. In the nematic liquid crystal (NLC)~ the molecules' long axes lie parallel to each other without formation of a layered structure. However, the domains in the nematics are arranged rather chaotically, and, even in the presence of orientational effects (for example, rubbing of KBr plates), some disorder is possible, something which will affect the dichroism value in this liquid-crystalli ne state. The phase transition from the nematic to the 'C" smectic state can occur during simple translation of the centers of gravity of the molecules with formation of alayered structure. But if the phase transition is to other types of smectic states, rotation of the molecules about the center of gravity is also possible. Thus, in a smectic liquid crystal (SLC) of type "C," the molecules are arranged in layers, and the inclination of the molecules in the layer with respect to the plane of the layer makes an angle close to 35 ~ [5]. During phase transition to a smectic state of type "D," this angle must change. Figure 1 shows the IR spectra of decyloxybenzoic acid in polarized light for various phase states. An identical sign of the dichroism of individual vibrational bands was observed in the phase states of the nematic liquid crystals, "C" smectic liquid crystals, and solid crystals, although the absolute value of the dichroism changed during nematic liquid-crystal-" C" smectic liquid-crystal-. ..- solid-crystal-ph as e transitions. In the "D" smectic liquid-crystalli ne state, the sign of the dichroism changed to the sign which was opposite to that of other phase states. This may indicate that the direction of the dipole moment of vibrational transitions of individual groups of atoms in the molecule changed by some angle in comparison with their location in the nematic liquid-crystalli ne, "C" smectic liquid-crystalli ne, and solid-crystallin e states. Reorientation of the molecules in the "D" smectic liquid crystals occurred with respect to their location in the "C" smectic liquid crystals. Table 1 gives the values of the dichroism and its sign for individual vibrational bands of decyloxybenzoic acid and the assignment of these bands according to the data of [6] and [7]. From Table 1, it is evident that the dichroism sign changed for the bands belonging both to the alkyl chain and to vibrations of the benzene ring. However, the d[chroism value of the bands belonging to vibrations of the benzene-ring skeleton was insignificant and differed little from their dichroism value in the "C" smectic liquidcrystalline and nematic liquid-crystalli ne states, although the sign of the dichroism changed to the opposite sign. This indicates that the location of the dipole moment of these groups of atoms changed by an angle close to 9 0 ~ in comparison with its location in the "C" smectic liquid-crystalli ne and nematic liquid-crystalli ne states. The maximum change in the dichroism value in the "C" smectic liquid crystals was observed in the band of benzene-ring bending vibrations. Apparently, during transition to this liquid-crystalli ne state from the nematic liquid-crystalli ne state, not only rotation of the benzene ring occurred, but also its rotation by some angle about the molecule's long axis so that the change in the dipole moment of this vibration lay in thedirec