Behaviour of a solvent trapped in a physical molecular gel

Abstract

Physical gels formed by amphiphilic molecules, namely in this study Methyl-4,6-O-benzylidene- -D-mannopyranoside, can be form either in polar and protic liquid-like water or in organic apolar solvent such as toluene. The solvent, that influences the supramolecular organization of the gelators, plays an important role in the stability and formation of the gel phase. Gelator–solvent interactions govern not only the assembly but also the solvent diffusion in the material. We present here measurements of neutron scattering (Time of Flight and Neutron Spin Echo) characterizing this microscopic behaviour. In addition, we show that transient grating spectroscopy provides valuable information through the characterization of the longitudinal acoustic wave propagating in the system. Opposite effects on the speed of sound in the gels are observed for the two solvents investigated, being relevant of the interactions between the gelators and the surrounding liquid.

Keywords:

• molecular gel
• physical gel
• neutron scattering
• Transient Grating Spectroscopy
• picosecond dynamics
• sound propagation

Acknowledgements

We thank Michel Bouriau for the help in setting up the TG experiment, and Thomas Derbomez for the help during the TG measurements. We also thank M.A. Gonzalez and J. Ollivier for their assistance during the experiments at the ILL.

Notes

No potential conflict of interest was reported by the authors.