Temperature dependence of the i.r. spectra of liquid crystalline p-heptoxybenzoic acid and p-octoxybenzoic acid

An FT-IR spectroscopic study of the role of hydrogen bonding in the formation of liquid crystallinity for mixtures containing bipyridines and 4-pentoxybenzoic acid

“…In each set of spectra, the high intensity C-H stretching signals are superimposed on a broad band centred at n $2900 cm À1 , associated with the fundamental vibration of hydrogen bonded hydroxyl groups, OH, and referred to as the A-type band. 8,51,52 Its appearance, together with the absence of contributions arising from free hydroxyl groups at n > 3500 cm À1 , is indicative of extensive hydrogen bonding. 53 This view is further supported by the observation of the B-type bands in the 2700-2500 cm À1 range, assigned to resonances between the fundamental stretch and in-plane bending of OH groups.…”

“…1(b), and this homologous series remains the focus of considerable research activity, see for example. [6][7][8][9][10] This concept in molecular engineering was later extended by Kato and Frechet, who mixed unlike hydrogen bond donors and hydrogen bond acceptors resulting in hydrogen bonded heterocomplexes, 2, and this approach is sketched in Fig. 1(c).…”

Hydrogen bonding and liquid crystallinity of low molar mass and polymeric mesogens containing benzoic acids: a variable temperature Fourier transform infrared spectroscopic study

“…The bands observed in the carbonyl region of the FTIR spectra for benzoic acids have been assigned to three differing species, namely, cyclic dimers ($1681 cm À1 ), open dimers ($1700 cm À1 ) and monomeric species (>1720 cm À1 ), which coexist in dynamic equilibrium, see Figure 9. [8,[53][54][55][56][57] We have performed a semi-quantitative assessment of the variation of the relative amounts of each of these species with temperature by deconvoluting the carbonyl band into three Lorentzian-Gaussian peaks, see Figure 10, and the temperature dependence of the relative area of each peak is shown in Figure 11. In the crystal phase, the lowest frequency contribution appears at unexpectedly low wavenumbers ($1670 cm À1 ).…”

Chemically Triggered Changes in Mechanical Properties of Responsive Liquid Crystal Polymer Networks with Immobilized Urease

“…The activation of LCN films with acyl fluoride groups as well as the incorporation of urease was monitored via attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) (Figure 2A). After treatment with XtalFluor-E, the C O antisymmetric stretching band at 1682 cm −1 , assigned to the carboxylic acid dimers, 32 shifted to a higher wavenumber (1801 cm −1 ). This shift is indicative of the acyl halide CO stretching, 33 signaling complete conversion of carboxylic acids to acyl fluorides.…”