Solvent contribution to the stability of a physical gel characterized by quasi-elastic neutron scattering

TL;DR

This study uses neutron scattering to analyze how solvent molecules contribute to the stability of a physical gel, revealing differences in solvent immobilization in water and toluene.

Contribution

It provides detailed insights into solvent immobilization in a physical gel using neutron scattering, highlighting the different interactions in water and toluene.

Findings

Few toluene molecules are immobilized per gelator.

Approximately 10-14 water molecules are immobilized per gelator.

Neutron scattering reveals solvent behavior in molecular gels.

Abstract

The dynamics of a physical gel, namely the Low Molecular Mass Organic Gelator {\textit Methyl-4,6-O-benzylidene-$\alpha$ -D-mannopyranoside ($\alpha$-manno)} in water and toluene are probed by neutron scattering. Using high gelator concentrations, we were able to determine, on a timescale from a few ps to 1 ns, the number of solvent molecules that are immobilised by the rigid network formed by the gelators. We found that only few toluene molecules per gelator participate to the network which is formed by hydrogen bonding between the gelators' sugar moieties. In water, however, the interactions leading to the gel formations are weaker, involving dipolar, hydrophobic or $\pi-\pi$ interactions and hydrogen bonds are formed between the gelators and the surrounding water. Therefore, around 10 to 14 water molecules per gelator are immobilised by the presence of the network. This study shows that neutron scattering can give valuable information about the behaviour of solvent confined in a molecular gel.