Gelating abilities of metal salts of ricinelaidic acid. Structural and rheological considerations

Abstract

The gelating abilities of metal salts of ricinelaidic acid (D‐REA), the trans isomer of the naturally occurring cis isomer, D‐ricinoleic acid, have been examined in a wide range of liquids. D‐REA is not a good gelator due to its bent shape and low melting temperature. Although upon the formation of metal salts aids aggregation of D‐REA, their gelating ability differs dramatically depending on the nature of the metal cation. The salts with nickel(II), copper(II), and zinc(II) are inefficient gelators, while the calcium salt can gelate various organic liquids and the sodium salt is an ambidextrous gelator. Also, gels of calcium and sodium salts in nitrobenzene and/or in water are among the few known examples with crystalline gelator networks that exhibit thixotropic behavior. Structural insights from FT‐IR and powder X‐ray diffraction indicate that the specific nature of interactions of the salts at their head groups leads to different packing arrangements and changes the strength of the driving forces for 1D growth from secondary interactions. A short comparison between the gelating abilities of the D‐REA and the corresponding salts from 9,10‐dioxooctadecanoic acid, an acid of related structure, is included as well. Insights into the relationships among the interactions at the metal carboxylate centers, their ability to form molecular gels, and the properties of their aggregated structures are provided.

Processable UiO-66 Metal–Organic Framework Fluid Gel and Electrical Conductivity of Its Nanofilm with Sub-100 nm Thickness

“…Rheological measurements of fluid gel revealed the shear-thinning behavior with increasing shear strain rate, which is the characteristic of non-Newtonian fluids (Figure a). , Further measurement of the storage modulus ( G ′) and loss modulus ( G ″) was also carried out as a function of angular frequency (Figure b). The phase angles of both G ′ and G ″ are independent of the frequency, and G ″ remains smaller than G ′ throughout the frequency range, showing characteristic properties of gel state. , It is noted that G ′ and G ″ of the gels decrease with the increasing applied strain and exhibit the flowing-fluid behavior at high strain. , The viscosity of fluid gel was found to be lower by approximately 3 orders of magnitude than that of the nonflowing gel (comparing between Figures a and S2a), suggesting more fluid behavior compared to the nonflowing gel . Therefore, the rheological properties of the fluid gel indicate the suitable viscoelasticity of UiO-66 in the fluid gel state for further fabrication as nanofilms.…”

“…The phase angles of both G′ and G″ are independent of the frequency, and G″ remains smaller than G′ throughout the frequency range, showing characteristic properties of gel state. 40,58 It is noted that G′ and G″ of the gels decrease with the increasing applied strain and exhibit the flowing-fluid behavior at high strain. 37,39 The viscosity of fluid gel was found to be lower by approximately 3 orders of magnitude than that of the nonflowing gel (comparing between Figures 3a and S2a), suggesting more fluid behavior compared to the nonflowing gel.…”