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

Elliot Christ (1) , Christophe Blanc (2) , Abdelaziz Al Ouahabi (1) , David Maurin (2) , Rozenn Le Parc (2) , Jean-Louis Bantignies (2) , Jean-Michel Guenet (1) , Dominique Collin (1) , Philippe J. Mesini (1)

1 ICS - Institut Charles Sadron
2 L2C - Laboratoire Charles Coulomb

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.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Elliot Christ, Christophe Blanc, Abdelaziz Al Ouahabi, David Maurin, Rozenn Le Parc, et al.. Origin of Invariant Gel Melting Temperatures in the c-T Phase Diagram of an Organogel. Langmuir, 2016, 32 (19), pp.4975-4982. ⟨10.1021/acs.langmuir.6b00995⟩. ⟨hal-01344912⟩