Origin of Invariant Gel Melting Temperatures in the c–T Phase Diagram of an Organogel

Abstract

Binary c-T phase diagrams of organogelators in solvent are frequently simplified to two domains, gel and sol, even when the melting temperatures display two distinct regimes, an increase with T and a plateau. Herein, the c-T phase diagram of an organogelator in solvent is elucidated by rheology, DSC, optical microscopy, and transmitted light intensity measurements. We evidence a miscibility gap between the organogelator and the solvent above a threshold concentration, cL. In this domain the melting or the formation of the gel becomes a monotectic transformation, which explains why the corresponding temperatures are nonvariant above cL. As shown by further studies by variable temperature FTIR and NMR, different types of H-bonds drive both the liquid-liquid phase separation and the gelation.

Infrared and Raman spectroscopy of non-conventional hydrogen bonding betweenN,N′-disubstituted urea and thiourea groups: a combined experimental and theoretical investigation

“…6 The resulting one-dimensional chains are present in many crystals.1 Therefore, conventional strong and predictable oxygencentered HB interactions (OCHB) in urea derivatives are classically used for the synthesis of crystalline solids 7 with various architectures,3 from one-dimensional chains and nanotubes, 8 to layered and three-dimensional frameworks. 9,10 Thiourea derivatives have been far less used as design elements in crystal engineering 1 despite the fact that they can also self-organize by N-H … S=C hydrogen-bonding. 11 The sulfurcentered hydrogen bonding (SCHB) interactions are considered as nonconventional in nature.…”

A pH-/thermo-responsive hydrogel formed from N,N′-dibenzoyl-l-cystine: properties, self-assembly structure and release behavior of SA

“…39 Temperature measured by rheology experiments in which G 0 ¼ G 00 is denoted as T gel . 40 As depicted in Fig. 4, both G 0 and G 00 almost keep constant at low temperature but decrease rapidly at T gel .…”

“…S4 in ESI †), and the temperature corresponding to the maximum of the peak in DSC curves is denoted as T DSC . 40 By visual inspection, the samples are liquids above T DSC , and then become into gels below T DSC . The T DSC proles of DBC hydrogels prepared by varying concentrations (Fig.…”

Structure of Nanotubes Self-Assembled from a Monoamide Organogelator

“…The esters and aromatic compounds are fully miscible with alkanes, but N -alkyl amides and alkanes show a liquid-liquid phase separation [ 29 ]. As we have shown, an amide containing gelator, leads to such a liquid-liquid phase separation in the sol [ 30 ]. The location of the ester chains is supported by the fact that the parameters of the fits provide an almost invisible outer and inner layer.…”